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Departments of 1 Psychology and of 4 Medicine, University of Washington, Seattle 98195; 3 Department of Veterans Affairs, Puget Sound Health Care System, Seattle 98108; and 2 Geriatric Research, Education and Clinical Center, Department of Veterans Affairs, Puget Sound Health Care System and Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington 98195
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ABSTRACT |
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 TOP
 ABSTRACT
 INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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The anatomic connections
of the paraventricular nucleus of the hypothalamus (PVN) are such that
it is ideally situated to modulate and/or control autonomic responses
to a variety of stressors, including hypoglycemia. In our experimental
model of hypoglycemia-associated autonomic failure (HAAF), a syndrome
in which the counterregulatory response to hypoglycemia is partially
compromised via unknown mechanisms, activation of the PVN is blunted
(15). We hypothesized that this blunted PVN activation
during HAAF may be sufficient to cause the impaired counterregulatory
response. To test this hypothesis, we anesthetized the PVN with
lidocaine during insulin-induced hypoglycemia in rats and measured
counterregulatory hormone levels. PVN inactivation decreased indexes of
the sympathoadrenal response (plasma epinephrine and norepinephrine)
and the hypothalamic-pituitary axis response (ACTH). Inactivation
decreased the peak epinephrine response to hypoglycemia by almost half
(
42 ± 6% from control; P = 0.04) and the peak
norepinephrine response by 34 ± 5% (P = 0.01).
The peak plasma ACTH levels attained were suppressed by 35 ± 6%
(P = 0.02). Adrenal corticosterone and pancreatic
glucagon responses were not impaired. This pattern of neuroendocrine
response is unlike that previously seen with our HAAF model. Control
infusions of lidocaine 
1 mm anterior or posterior to the PVN did not
simulate this neuroendocrine pattern. Thus it appears that decreased
PVN activation, as occurs with HAAF, may be involved in specific
components of HAAF (i.e., blunting the sympathoadrenal and
hypothalamic-pituitary-adrenocortical axis response), but
not in others (i.e., blunting the glucagon response).
paraventricular nucleus; hypothalamus; stress; rat; lidocaine
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INTRODUCTION |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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THE PARAVENTRICULAR NUCLEUS (PVN) of the hypothalamus responds to physiological and psychological stressors (21) by increasing the synthesis and release of vasopressin (VP) and corticotropin-releasing factor (CRF), which stimulate the release of ACTH from the pituitary (57) and, consequently, release of glucocorticoids (e.g., corticosterone) from the adrenal cortex. The PVN also sends direct projections to autonomic preganglionic cells in the spinal cord and parasympathetic nuclei in the brain stem (23, 36, 46, 50) and may activate the sympathetic and parasympathetic nervous systems through these autonomic centers (4, 22, 58). Adrenomedullary epinephrine release secondary to sympathetic activation, in concert with plasma corticosterone, represents the essential neuroendocrine response to stressors. This response may be reduced on repeated challenge with that same stressor (7-10, 17). A clinically important example of a blunted neuroendocrine response to a repeated physiological stressor is the defective counterregulatory response to repeated hypoglycemia in insulin-requiring diabetic patients, known as hypoglycemia-associated autonomic failure (HAAF) (9). Hypoglycemia stimulates the neuroendocrine response described above, as well as glucagon release by the pancreas, and pituitary growth hormone release. HAAF is the blunting of these responses after repeated hypoglycemic episodes, as can happen with intensive insulin therapy.
HAAF has been modeled experimentally in both human subjects (11, 12) and animals (45). We previously reported (15) that repeated bouts of insulin-induced hypoglycemia in rats result in HAAF (decreased epinephrine, glucagon, and corticosterone responses to hypoglycemia). Concomitantly, activation of several hypothalamic nuclei, including the PVN, was blunted. Hypoglycemia after prior intracerebroventricular corticosterone did not produce HAAF. In those rats, activation of hypothalamic nuclei was blunted except for the PVN. Therefore, we hypothesized that decreased PVN activation might be a determining factor for the impaired neuroendocrine response seen during repeated hypoglycemia. To test this hypothesis in the current study, we induced hypoglycemia in rats to a level comparable to our prior study while inactivating the PVN by infusion of lidocaine. We predicted that anesthetizing the PVN would blunt the neuroendocrine response to hypoglycemia in a manner similar to the blunted neuroendocrine response caused by antecedent hypoglycemia.
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METHODS |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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Subjects. Male Wistar rats (Simonsen Laboratories, Gilroy, CA; 350-400 g) were maintained on a 12:12-h light-dark schedule (lights on at 7 AM; lights off at 7 PM) with ad libitum access to food and water and were studied during the lights-on portion of the light cycle. All procedures were approved by the Animal Studies Subcommittee of the Department of Veterans Affairs Puget Sound Health Care System Research and Development Committee and adhere to the "Guiding Principles for Research Involving Animals and Human Beings" set forth by the American Physiological Society (3).
Surgery.
All animals underwent bilateral implantation of intravenous Silastic
catheters according to the method of Scheurink et al. (42)
under ketamine-xylazine anesthesia [60 mg/kg ketamine (KetaFlo, Abbott
Laboratories, Chicago, IL), 7.8 mg/kg xylazine (Xyla-Ject, Phoenix
Pharmaceutical, St. Joseph, MO)] with supplemental doses (25 mg/kg) of
ketamine when necessary. One catheter was placed in the linguofacial
vein and the other in the submaxillary vein and advanced to the right
atrium. Catheters were tunneled subcutaneously and exteriorized through
a midline incision in the scalp. Rats were then placed in a stereotaxic
frame (David Kopf Instruments, Tujunga, CA), and bilateral 26-gauge
stainless steel guide cannulas (Plastics One, Roanoke, VA) were
implanted, aimed at the PVN using the stereotaxic coordinates 2.2
anteroposterior, ± 0.5 mediolateral, 7.0 dorsoventral from bregma
according to the atlas of Paxinos and Watson (40).
Two separate control groups received cannulas either 1 mm anterior to
the PVN placement [control anterior (CA); n = 11] or
1 mm posterior to the PVN placement [control posterior (CP);
n = 8]. The intracranial cannulas and intravenous
catheters were held in place by acrylic cement (Lang Dental, Wheeling,
IL) to four skull screws (Small Parts, Miami Lakes, FL). Animals
received 3 ml sc lactated Ringer solution (Baxter Pharmaceutical
Products, New Providence, NJ) and 0.2 ml im Gentamicin antibiotic
(Bayer, Leverkusen, Germany) and were maintained on a circulating-water heating pad until recovery from anesthesia. Catheter lines were filled
with 25-60% polyvinylpyrrolidone (PVP10, Sigma, St. Louis, MO)/heparin (1,000 U/ml; Elkins-Sinn, Cherry Hill, NJ) and kept patent
by a heparin (100 U/ml) flush every 3 days. All animals were allowed to
reach their presurgery weights (~7 days) before study.
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Experimental procedures.
Before performing experiments, animals were familiarized with square
acrylic test chambers (~30 × 30 × 30 cm) by being placed in them for several hours each day for 2-3 days (at least 1 patency check was done during this time). The bottoms of the test
chambers were removable and held bedding while occupied by the animals. After this, all animals were subjected to a 2-day procedure. On day 1, animals were allowed to acclimate to the test
chambers for 30 min and given a 10-min PVN infusion of 0.1 M
PBS vehicle (pH = 7.4; Oxoid, Bastingstoke, UK) to habituate the
animals to the infusion procedure. On day 2, the animals
were placed in the test chambers for at least 2 h before
experimental procedures began. Injection and withdrawal cannulas were
connected, and the experiment began once the animals were observed to
be "calm" (~10-15 min after connecting cannulas). The
preexperiment habituation sessions in the test chambers, preexperiment
patency checks, and the day 1 injection procedure ensured
well-adapted animals and relatively stress-free baseline conditions on
day 2. Animals received insulin (Novolin R, regular human
insulin, recombinant DNA origin, Novo Nordisk, Princeton, NJ; 0.5 U · 100 g body
wt · h
1 iv) over 120 min along with
PVN infusions of lidocaine (2%; Sigma; n = 10) or
vehicle (n = 11). Infusions were carried out by
programmable syringe pumps (SP101i, World Precision Instruments,
Sarasota, FL). The time course and number of intracerebral infusions
are given in Fig. 2. This timing was
based on the functional pharmacokinetics of lidocaine in brain tissue
(33, 47) and the goal of establishing a lidocaine block of
PVN neuronal activity for the duration of the insulin infusion. Data
from a number of studies indicate that a single infusion of lidocaine
at this dose anesthetizes various regions of the central nervous
system, including the PVN, for approximately 15-20 min (1,
2, 16, 33, 35, 39, 44, 47, 56). Therefore, a 10-min infusion was
made every 25 min. Lidocaine was infused at a rate of 0.1 µl/min, a
rate that causes no discernible tissue damage on histological
evaluation (unpublished observations). The volume of functional spread
in brain tissue is 
1.0 mm3 for this rate and
volume of infusion [based on studies using similar and higher
rates/volumes (1, 6, 29, 34, 39, 44, 47)]. Blood samples
(1.5 ml) were drawn every 30 min and immediately replaced with donor
blood drawn from unstressed rats immediately before the day
2 procedure. The same procedure was carried out for the two
anatomic control groups, CA and CP.
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Histology.
After the day 2 infusions, each animal was overdosed with
pentobarbital sodium (Nembutal, Abbott Laboratories, Chicago, IL), 0.3 µl of fast green dye (VWR, West Chester, PA) was infused into the PVN
to mark the site of injection, and then animals were perfused transcardially with 0.9% saline followed by 4% paraformaldehyde. Brains were removed and placed in 4% paraformaldehyde at 4°C for 3 days. Brains were submersed in 30% sucrose followed by freezing at
80°C in embedding media (Fisher, Pittsburgh, PA), until sectioning at 40 µm. Tissue sections were mounted on slides and checked for cannula placement. Only neuroendocrine data from animals with correctly
placed cannulas were included in data analysis.
Plasma assays.
Blood samples were obtained for the measurement of neuroendocrine
responses and stored at 80°C until assayed. Assays were as
described previously (15). Blood for the catecholamine
assays was collected on EGTA:glutathione (2.3 mg/ml:1.5 mg/ml; Sigma). Tubes for glucagon assays contained 10 µl of 1 M benzamidine (Sigma) and 1 U heparin. Blood for glucose, corticosterone, and ACTH assays was
collected on EDTA and aprotinin (0.7 trypsin inhibitor unit; Sigma). A radioenzymatic method as described in Evans et al.
(14) was used for determination of plasma epinephrine and
norepinephrine. An RIA procedure was used for plasma corticosterone
measurement as described in van Dijk et al. (53). Plasma
glucose was measured spectrophotometrically, after a glucose oxidase
reaction, with a Dynatech MR5000 microplate reader connected to a
personal computer running Dynatech Biolinx software (Dynatech
Laboratories, Chantilly, VA). Glucagon was assayed by the Linco
glucagon RIA kit (Linco Research, St. Charles, MO).
Measurements of ACTH were made using the Nichols Institute Diagnostics
immunoradiometric assay kit (Nichols Institute Diagnostics, San Juan
Capistrano, CA).
Statistical analysis.
Data from the plasma assays were analyzed using repeated-measures ANOVA
with time as the repeated measure and treatment (vehicle or
lidocaine) as the between-groups factor. In the event of
significant main effects or interactions, Fisher's protected least
significant difference post hoc tests were done to determine
significant differences, and t-tests were done where
appropriate. Data expressed as percentage of control were analyzed
using ANOVA, with treatment (lidocaine, vehicle, or repeated
hypoglycemia) as the between-groups factor. Significance for all tests
was taken as P 0.05.
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RESULTS |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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PVN inactivation and the counterregulatory response.
Both vehicle and lidocaine PVN rats demonstrated significant decreases
in plasma glucose during intravenous insulin infusion (Table
1; main effect of time:
F4,17 = 353, P < 0.0001).
The declines in plasma glucose levels did not differ between the two groups (Table 1; no interaction between time and treatment:
F4,68 = 1.02, P = 0.40).
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11
pg/ml) but significant decrease in ACTH at time 0 (P = 0.05; Table 1). This difference disappeared by 30 min into the hypoglycemia (P = 0.44), and the plasma
ACTH levels in the lidocaine and vehicle groups remained similar to
each other until 90 min, at which point the lidocaine group
demonstrated lower plasma ACTH at both 90 and 120 min (Table 1;
interaction between time and treatment:
F4,68 = 2.6, P = 0.02).
Despite the effect on plasma ACTH levels, the peripheral release of
corticosterone was not significantly affected by intra-PVN lidocaine
(Table 1; no effect of treatment: F1,17 = 1.17, P = 0.29; and no interaction between time and
treatment: F4,68 = 0.77, P = 0.55).
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82 pg/ml (P = 0.009) and again at 60 min (P = 0.046) and maximally blunted at
120 min (3,084 pg/ml; P = 0.044) in this group (Table
1; interaction between treatment and time:
F4,68 = 3.15, P = 0.01).
The increase of plasma norepinephrine was also blunted by PVN
lidocaine. The peak plasma norepinephrine concentration decreased by
34 ± 5% (P = 0.013 vs. control; Fig. 3; effect
of treatment: F1,17 = 7.7, P = 0.01). Plasma norepinephrine levels in the
lidocaine group were slightly lower at time 0 (85 pg/ml;
P = 0.002) but returned to control levels until 120 min
when they were decreased 453 pg/ml (P = 0.01)
relative to vehicle (Table 1; interaction between treatment and time:
F4,68 = 2.72, P = 0.037).
PVN lidocaine did not alter pancreatic glucagon release in response to
hypoglycemia (Fig. 3; Table 1; no interaction between time and
treatment: F4,68 = 1.04, P = 0.39).
Inactivation of regions surrounding the PVN. Cannulas were placed 1 mm anterior to the PVN (CA) and 1 mm posterior to the PVN (CP) at the same dorsoventral coordinate to test if diffusion of the lidocaine to adjacent structures may have produced the changes in the counterregulatory response. Lidocaine infusion in the CA group did not alter the decline of plasma glucose (Table 2; no effect of treatment: F1,9 = 0.17, P = 0.69; no treatment-time interaction: F4,36 = 0.65, P = 0.63). Unlike intra-PVN lidocaine, CA lidocaine did not blunt the hypoglycemia-induced rise in plasma ACTH, corticosterone, epinephrine, norepinephrine, or glucagon (Table 2 and Fig. 4). Lidocaine infusion in the CP rats did not alter the decline of plasma glucose during hypoglycemia (Table 2; no effect of treatment: F1,6 = 1.04, P = 0.35; no treatment-time interaction: F4,24 = 0.78, P = 0.55). CP lidocaine did not blunt the hypoglycemia-induced rise in plasma ACTH, corticosterone, or glucagon (Table 2 and Fig. 4). The plasma catecholamine response to hypoglycemia was decreased by lidocaine infusion in the CP group (epinephrine, effect of treatment: F1,6 = 15.6, P = 0.008; epinephrine, treatment-time interaction: F4,24 = 6.3, P = 0.001; norepinephrine, effect of treatment: F1,6 = 6.5, P = 0.043; norepinephrine, treatment-time interaction: F4,24 = 3.8, P = 0.016). Peak epinephrine and norepinephrine levels were decreased by 57 ± 4% (P = 0.0003) and 41 ± 2% (P = 0.005), respectively (Fig. 4) at the last time point (120 min) (P = 0.003 and 0.005, respectively; Table 2).
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DISCUSSION |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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Figure 5 summarizes the primary
findings of this study and compares the results of PVN inactivation
with those we observed in HAAF (15). Although plasma
glucose levels decreased equivalently for vehicle and lidocaine
treatments within the PVN group (Table 1), the counterregulatory
response was not equivalent for those treatments. Lidocaine block of
PVN activity resulted in two types of changes in the levels of plasma
ACTH and the catecholamines measured during the 2-h insulin infusion.
One change was a small decrease (compared with later changes) in the
baseline levels of these hormones. This change disappeared during the
session (see RESULTS and Table 1). The other change, larger
in magnitude, was a blunting of the rise in the levels of these
hormones during the peak of the neuroendocrine response to hypoglycemia
(see RESULTS, Table 1, and Fig. 3). Both of these changes
may reflect a role of the PVN in increasing the level of activation or
the "tone" of the hypothalamic-pituitary-adrenocortical axis and
autonomic nervous system. This is consistent with other findings of
modest baseline effects of PVN inactivation/stimulation on indexes of autonomic function (see below) (16, 27, 32, 39, 55).
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PVN lidocaine resulted in decreased release of ACTH. Because CRF and AVP, two factors that regulate ACTH release from the pituitary, are released by parvocellular PVN neurons (31), this is an expected outcome. In fact, this degree of blunting of the ACTH response appears to be the same as that achieved with prior hypoglycemia in the HAAF model (15; Fig. 5). A complete block of ACTH release was not observed, perhaps because 1) CRF and AVP are not the sole factors that regulate ACTH release (25, 37, 52), nor is the PVN the sole regulator of ACTH release (5); 2) even with permanent physical lesion of the PVN, stimulated ACTH release is not always completely abolished; and 3) the lidocaine infusions may not have inactivated the entire population of CRF and AVP neurons in all the rats.
Concomitant with the decrease in ACTH, one might have predicted a decrease in plasma corticosterone as well. In the HAAF model, corticosterone was indeed modestly but significantly blunted at 120 min. In the current study, the rise in corticosterone was not significantly blunted by PVN lidocaine (Table 1). It is possible that the adrenal cortex response may be maximal even at the blunted level of ACTH seen in the lidocaine rats: ACTH-induced corticosterone secretion plateaus even with increasing levels of plasma ACTH (26, 51). It is also possible that the reduction in ACTH in the lidocaine group translates into a shortened duration of corticosterone response. It has been shown across species that increases in plasma ACTH can increase the duration of the glucocorticoid response without affecting the amplitude of that response (26, 28, 54). Thus in the current study, decreased plasma ACTH in the PVN lidocaine rats might decrease the duration of the corticosterone response. This might in fact be occurring in our animals, because the level of corticosterone at t = 60 min was not different from the level at t = 120 min in the PVN lidocaine rats (P = 0.33 by 2-tailed t-test; 185 ± 7 vs. 195 ± 6 µg/dl), while in the PVN vehicle rats, corticosterone was still rising from t = 60 min to t = 120 min (P = 0.005; 179 ± 8 vs. 219 ± 8 µg/dl). However, this remains speculative because we observed no difference between the treatment groups (lidocaine vs. vehicle) over time (no time-treatment interaction: P = 0.55). Another possibility, but also speculative, is based on evidence that autonomic innervation of the adrenal gland may decrease adrenal sensitivity to ACTH, an effect that is removed (i.e., adrenals are disinhibited) by denervating the adrenals (24). If, as reflected in plasma norepinephrine and epinephrine, PVN lidocaine results in decreased sympathetic activity, the adrenals may be more sensitive to ACTH (i.e., disinhibited) and thus produce increased plasma corticosterone at lower levels of ACTH.
PVN lidocaine also resulted in blunted adrenomedullary epinephrine release as reflected in decreased plasma epinephrine levels and in decreased plasma norepinephrine relative to vehicle controls (Table 1; Fig. 3). This indicates that PVN inactivation reduces the adrenomedullary response to hypoglycemia as well as the overall sympathetic nervous system response. Thus the PVN plays a role in maintaining the sympathoadrenal response to hypoglycemia. This is consistent with the anatomic data showing that a number of neurons in the PVN project directly to autonomic nuclei in the brain stem and spinal cord (23, 30, 36, 46, 50). These neurons are found throughout the PVN (especially in the dorsal and lateral areas) and include a small number originating in the magnocellular PVN (see Figs. 2 and 4 in Ref. 30). The functionality of these neurons has been demonstrated in numerous physiological experiments (e.g., Refs. 16, 27, 32, 39, 55) demonstrating changes in autonomic indexes such as blood pressure, sympathetic nerve activity, gastric motility, and plasma epinephrine and norepinephrine levels with PVN stimulation. To our knowledge the current study is the first demonstrating that alteration of activity of PVN neurons changes the sympathoadrenal response to hypoglycemia, although the probable anatomic basis for this has been established (23, 36, 38, 46, 50). The somewhat modest effect seen here is consistent with findings by others either measuring plasma catecholamines (32, 41) or other physiological endpoints of sympathetic activity (39, 56) after PVN manipulations. Interestingly, the plasma norepinephrine response was not altered or blunted with HAAF in our previous study (15), even though c-FOS staining indicated that PVN activation was markedly blunted with HAAF. This may indicate that the activity of other brain structures involved in the control of the sympathetic response resulted in a stimulation of norepinephrine output masking the inhibitory component of PVN blunting.
The pancreatic glucagon response is blunted in our HAAF model, but was not after PVN inactivation (Fig. 5). This response has been shown to be maintained by redundant sympathetic and parasympathetic autonomic inputs. All of these inputs need to be compromised to significantly decrease the glucagon response (19, 20). This suggests that HAAF disrupts these inputs more completely than PVN inactivation alone, again indicating the involvement of other brain regions and/or peripheral structures in addition to the PVN in HAAF. Recently, Schöfl et al. (43) have demonstrated that in a population of patients with damage to the hypothalamus as a result of craniopharyngioma, the sympathoadrenal response to hypoglycemia was abolished while the sympathetic response to orthostatic challenge was unchanged. They found no change in the glucagon response in these patients, indicating that central nervous system sites that may modulate the glucagon response may not be in the hypothalamus (see below) and are not the same sites modulating sympathetic responses. Although the extent of damage in these patients was not reported, and basal medial structures such as the ventromedial nucleus probably regulate sympathetic activity as well (41), the finding does suggest that activation of hypothalamic structures is important and specific for the sympathoadrenal component of the response to hypoglycemia.
We are confident of the anatomic specificity of the effects of our
lidocaine infusions into the PVN for a number of reasons. The
literature indicates that the volume of functional spread of lidocaine
in brain tissue is 1.0 mm3 for this rate and volume of
infusion [based on studies using similar and higher rates/volumes
(1, 6, 29, 34, 39, 44, 47)]. Additionally, Patel and
Schmid (39) showed that lidocaine injected just dorsal or
lateral to the PVN did not produce alterations of autonomic function,
while intra-PVN injections did (see Fig. 4 in Ref. 39). In
the CP group, lidocaine infusion 1 mm posterior to the PVN produced an
effect that was distinct from that in the PVN group. CP lidocaine did
not alter baseline (time 0) levels of hormones, and the
catecholamine response to hypoglycemia was curtailed at the final time
point. There was no change in the ACTH response, suggesting no
diffusion into the PVN. Examination of the brain sections from the CP
group revealed that the infusions occurred just above the dorsomedial
nucleus of the hypothalamus (DMH). The DMH is known to have anatomic
projections to the PVN, as well as autonomic cell groups in the brain
stem (48, 49), and studies have demonstrated that
stimulation or inhibition of the DMH results in autonomic changes
(13, 18, 59). We are currently evaluating the potential
contribution of the DMH to the normal response to hypoglycemia and to
HAAF. In the CA group, injections 1 mm anterior to the PVN had no
effect on the rise in catecholamines or ACTH in response to
hypoglycemia, indicating no diffusion beyond 1 mm into the PVN.
Perspectives
We previously reported that there is a dramatic decrease in hypoglycemia-induced activation of the PVN after prior hypoglycemia (15). Anatomically, the blunting was relatively homogeneous across the PVN, not favoring what has been considered an "autonomic region." In attempting to replicate this homogeneous inactivation, we infused lidocaine into the PVN during hypoglycemia. Anesthetizing the PVN resulted in a blunting of the autonomic and HPA components of the counterregulatory response, similar to that produced by repeated hypoglycemia. The complete counterregulatory response, however, may require activation of both PVN and areas such as the arcuate and dorsomedial hypothalamic nuclei and posterior hypothalamic regions. Additionally, endocrine tissues (e.g., pancreatic
-cells,
adrenomedullary cells, etc.) and/or the peripheral innervation of these
tissues may have a role in these phenomena, changing release parameters
and/or sensitivity to neurotransmitters and humoral factors. Thus while
PVN activation must play a critical role in the sympathoadrenal
response to hypoglycemia, it is not responsible for the complete
counterregulatory response to a single bout of hypoglycemia, and its
inactivation cannot be solely responsible for the impaired
counterregulatory response that occurs with multiple bouts of hypoglycemia.
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ACKNOWLEDGEMENTS |
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We thank A. Scheurink (Univ. of Groningen, Groningen, the Netherlands) for helpful discussion regarding the experimental procedures. We gratefully acknowledge the technical efforts of the Metabolism Laboratory staff, J. Wade, R. Hollingworth, and K. Cueno for glucose and catecholamine assays. The technical assistance of E. Colasurdo and C. Sikkema with corticosterone and ACTH assays is gratefully acknowledged. The technical assistance of A. Zavosh with glucagon assays is greatly appreciated. We thank M. Hoen for histological preparations.
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FOOTNOTES |
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Support for these studies was provided by grants from the American Diabetes Association, the Juvenile Diabetes Foundation, and the Department of Veterans Affairs Merit Review Program. S. B. Evans is supported by a Dick and Julia McAbee Endowed Fellowship in Diabetes Research. G. J. Taborsky, Jr., received support from National Institute of Diabetes and Digestive and Kidney Diseases Grant R01-DK-50,154. D. P. Figlewicz is also supported by NIDDK Grant R01-DK-40,963.
Address for reprint requests and other correspondence: S. B. Evans, VA Puget Sound Health Care System, Metabolism (151), 1660 South Columbian Way, Seattle, WA 98108 (E-mail:ngevans{at}u.washington.edu).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
October 10, 2002;10.1152/ajpregu.00439.2002
Received 22 July 2002; accepted in final form 20 September 2002.
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REFERENCES |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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1.
Albert, DJ,
and
Madryga FJ.
An examination of the functionally effective spread of 4 microliters of slowly infused lidocaine.
Behav Neural Biol
29:
378-384,
1980[ISI][Medline].
2.
Albert, DJ,
and
Wong RCK
Hyperreactivity, muricide, and intraspecific aggression in the rat produced by infusion of local anesthetic into the lateral septum or surrounding areas.
J Comp Physiol Psychol
92:
1062-1073,
1978[ISI][Medline].
3.
American Physiological Society.
Guiding principles for research involving animals and human beings.
Am J Physiol Regul Integr Comp Physiol
283:
R281-R283,
2002
4.
Arancibia, S,
Rage F,
Astier H,
and
Tapia-Arancibia L.
Neuroendocrine and autonomous mechanisms underlying thermoregulation in cold environment.
Neuroendocrinology
64:
257-267,
1996[ISI][Medline].
5.
Bailey, TW,
and
DiMicco JA.
Chemical stimulation of the dorsomedial hypothalamus elevates plasma ACTH in conscious rats.
Am J Physiol Regul Integr Comp Physiol
280:
R8-R15,
2001
6.
Barnes, SJ,
Floresco SB,
Kornecook TJ,
and
Pinel JP.
Reversible lesions of the rhinal cortex produce delayed non-matching-to-sample deficits in rats.
Neuroreport
11:
351-354,
2000[ISI][Medline].
7.
Bhatnagar, S,
and
Dallman MF.
Neuroanatomical basis for facilitation of hypothalamic-pituitary-adrenal responses to a novel stressor after chronic stress.
Neuroscience
84:
1025-1039,
1998[ISI][Medline].
8.
Bhatnagar, S,
Viau V,
Chu A,
Soriano L,
Meijer OC,
and
Dallman MF.
A cholecystokinin-mediated pathway to the paraventricular thalamus is recruited in chronically stressed rats and regulates hypothalamic-pituitary-adrenal function.
J Neurosci
20:
5564-5573,
2000
9.
Cryer, PE.
Symptoms of hypoglycemia, thresholds for their occurrence, and hypoglycemia unawareness.
Endocrinol Metab Clin North Am
28:
495-500,
1999.
10.
Davis, SN,
Shavers C,
Costa F,
and
Mosqueda-Garcia R.
Role of cortisol in the pathogenesis of deficient counterregulation following antecedent hypoglycemia in normal humans.
J Clin Invest
98:
680-691,
1996[ISI][Medline].
11.
Davis, SN,
Shavers C,
Mosqueda-Garcia R,
and
Costa F.
Effects of differing antecedent hypoglycemia on subsequent counterregulation in normal humans.
Diabetes
46:
1328-1335,
1997[Abstract].
12.
Davis, SN,
Tate DB,
and
Costa F.
Effects of one episode of hypoglycemia on counterregulatory responses to subsequent short term hypoglycemia.
Diabetes
48, Suppl 1:
A124,
1999.
13.
DiMicco, JA,
and
Abshire VM.
Evidence for GABAergic inhibition of a hypothalamic sympathoexcitatory mechanism in anesthetized rats.
Brain Res
402:
1-10,
1987[ISI][Medline].
14.
Evans, MI,
Halter JB,
and
Porte D.
Comparison of double- and single-isotope enzymatic derivative methods for measuring catecholamines in human plasma.
Clin Chem
24:
567-570,
1978
15.
Evans, SB,
Wilkinson CW,
Bentson K,
Gronbeck P,
Zavosh A,
and
Figlewicz DP.
PVN activation is suppressed by repeated hypoglycemia but not antecedent corticosterone in the rat.
Am J Physiol Regul Integr Comp Physiol
281:
R1426-R1436,
2001
16.
Flanagan, LM,
Dohanics J,
Verbalis JG,
and
Stricker EM.
Gastric motility and food intake in rats after lesions of hypothalamic paraventricular nucleus.
Am J Physiol Regul Integr Comp Physiol
263:
R39-R44,
1992
17.
Garcia, A,
Marti O,
Valles A,
Dal-Zotto S,
and
Armario A.
Recovery of the hypothalamic-pituitary-adrenal response to stress. Effects of stress intensity, stress duration and previous stress exposure.
Neuroendocrinology
72:
114-125,
2000[ISI][Medline].
18.
Greenwood, B,
and
DiMicco JA.
Activation of the hypothalamic dorsomedial nucleus stimulates intestinal motility in rats.
Am J Physiol Gastrointest Liver Physiol
268:
G514-G521,
1995
19.
Havel, PJ,
and
Ahren B.
Activation of autonomic nerves and the adrenal medulla contributes to increased glucagon secretion during moderate insulin-induced hypoglycemia in women.
Diabetes
46:
801-807,
1997[Abstract].
20.
Havel, PJ,
Parry SJ,
Stern JS,
Akpan JO,
Gingerich RL,
Taborsky GJ, Jr,
and
Curry DL.
Redundant parasympathetic and sympathoadrenal mediation of increased glucagon secretion during insulin-induced hypoglycemia in conscious rats.
Metabolism
43:
860-866,
1994[ISI][Medline].
21.
Herman, JP,
and
Cullinan WE.
Neurocircuitry of stress: central control of the hypothalamo-pituitary-adrenocortical axis.
Trends Neurosci
20:
78-84,
1997[ISI][Medline].
22.
Hierlihy, LE,
Wallace JL,
and
Ferguson AV.
Autonomic pathways in development of neural stimulation-induced gastric mucosal damage.
Am J Physiol Gastrointest Liver Physiol
266:
G179-G185,
1994
23.
Hosoya, Y,
Sugiura Y,
Okado N,
Loewy AD,
and
Kohno K.
Descending input from the hypothalamic paraventricular nucleus to sympathetic preganglionic neurons in the rat.
Exp Brain Res
85:
10-20,
1991[ISI][Medline].
24.
Jasper, MS,
and
Engeland WC.
Splanchnicotomy increases adrenal sensitivity to ACTH in nonstressed rats.
Am J Physiol Endocrinol Metab
273:
E363-E368,
1997
25.
Jorgensen, H,
Knigge U,
Kjaer A,
Vadsholt T,
and
Warberg J.
Serotonergic involvement in stress-induced ACTH release.
Brain Res
811:
10-20,
1998[ISI][Medline].
26.
Keller-Wood, ME,
Shinsako J,
and
Dallman MF.
Integral as well as proportional adrenal responses to ACTH.
Am J Physiol Regul Integr Comp Physiol
245:
R53-R59,
1983
27.
Kubo, T,
Hagiwara Y,
Sekiya D,
Chiba S,
and
Fukumori R.
Cholinergic inputs to rostral ventrolateral medulla pressor neurons from hypothalamus.
Brain Res Bull
53:
275-282,
2000[ISI][Medline].
28.
Lay, DC, Jr,
Friend TH,
Randel RD,
Jenkins OC,
Neuendorff DA,
Kapp GM,
and
Bushong DM.
Adrenocorticotropic hormone dose response and some physiological effects of transportation on pregnant Brahman cattle.
J Anim Sci
74:
1806-1811,
1996[Abstract].
29.
Levy, R,
Lang AE,
Dostrovsky JO,
Pahapill P,
Romas J,
Saint-Cyr J,
Hutchison WD,
and
Lozano AM.
Lidocaine and muscimol microinjections in subthalamic nucleus reverse Parkinsonian symptoms.
Brain
124:
2105-2118,
2001
30.
Loewy, AD.
Forebrain nuclei involved in autonomic control.
Prog Brain Res
87:
253-268,
1991[ISI][Medline].
31.
Makara, GB.
The relative importance of hypothalamic neurons containing corticotropin-releasing factor or vasopressin in the regulation of adrenocorticotropic hormone secretion.
Ciba Found Symp
168:
43-51,
1992[Medline].
32.
Martin, DS,
and
Haywood JR.
Sympathetic nervous system activation by glutamate injections into the paraventricular nucleus.
Brain Res
577:
261-267,
1992[ISI][Medline].
33.
Martin, JH.
Autoradiographic estimation of the extent of reversible inactivation produced by microinjection of lidocaine and muscimol in the rat.
Neurosci Lett
127:
160-164,
1991[ISI][Medline].
34.
Martin, JH,
and
Ghez C.
Pharmacological inactivation in the analysis of the central control of movement.
J Neurosci Methods
86:
145-159,
1999[ISI][Medline].
35.
Martin, JH,
and
Ghez C.
Red nucleus and motor cortex: parallel motor systems for the initiation and control of skilled movement.
Behav Brain Res
28:
217-223,
1988[ISI][Medline].
36.
Motawei, K,
Pyner S,
Ranson RN,
Kamel M,
and
Coote JH.
Terminals of paraventricular spinal neurones are closely associated with adrenal medullary sympathetic preganglionic neurones: immunocytochemical evidence for vasopressin as a possible neurotransmitter in this pathway.
Exp Brain Res
126:
68-76,
1999[ISI][Medline].
37.
Oliver, C,
Conte-Devolx B,
Giraud P,
Gillioz P,
Lissitzky JC,
and
Boudouresque F.
Hypothalamic control of ACTH secretion.
Horm Res
13:
230-241,
1980[ISI][Medline].
38.
Pacak, K,
and
Palkovits M.
Stressor specificity of central neuroendocrine responses: implications for stress-related disorders.
Endocr Rev
22:
502-548,
2001
39.
Patel, KP,
and
Schmid PG.
Role of paraventricular nucleus (PVH) in baroreflex-mediated changes in lumbar sympathetic nerve activity and heart rate.
J Auton Nerv Syst
22:
211-219,
1988[ISI][Medline].
40.
Paxinos, G,
and
Watson C.
Atlas of the Rat Brain in Stereotaxic Coordinates. New York: Academic, 1986.
41.
Saito, M,
Minokoshi Y,
and
Shimazu T.
Accelerated norepinephrine turnover in peripheral tissues after ventromedial hypothalamic stimulation in rats.
Brain Res
481:
298-303,
1989[ISI][Medline].
42.
Scheurink, AJ,
Steffens AB,
Bouritius H,
Dreteler GH,
Bruntink R,
Remie R,
and
Zaagsma J.
Adrenal and sympathetic catecholamines in exercising rats.
Am J Physiol Regul Integr Comp Physiol
256:
R155-R160,
1989
43.
Schöfl, C,
Schleth A,
Berger D,
Terkamp C,
von zur Muhlen A,
and
Brabant G.
Sympathoadrenal counterregulation in patients with hypothalamic craniopharyngioma.
J Clin Endocrinol Metab
87:
624-629,
2002
44.
Seamans, JK,
Floresco SB,
and
Phillips AG.
Functional differences between the prelimbic and anterior cingulate regions of the rat prefrontal cortex.
Behav Neurosci
109:
1063-1073,
1995[ISI][Medline].
45.
Shum, K,
Inouye K,
Chan O,
Mathoo J,
Bilinski D,
Matthews SG,
and
Vranic M.
Effects of antecedent hypoglycemia, hyperinsulinemia, and excess corticosterone on hypoglycemic counterregulation.
Am J Physiol Endocrinol Metab
281:
E455-E465,
2001
46.
Strack, AM,
Sawyer WB,
Platt KB,
and
Loewy AD.
CNS cell groups regulating the sympathetic outflow to adrenal gland as revealed by transneuronal cell body labeling with pseudorabies virus.
Brain Res
491:
274-296,
1989[ISI][Medline].
47.
Tehovnik, EJ,
and
Sommer MA.
Effective spread and timecourse of neural inactivation caused by lidocaine injection in monkey cerebral cortex.
J Neurosci Methods
74:
17-26,
1997[ISI][Medline].
48.
Ter Horst, GJ,
and
Luiten PG.
The projections of the dorsomedial hypothalamic nucleus in the rat.
Brain Res Bull
16:
231-248,
1986[ISI][Medline].
49.
Thompson, RH,
Canteras NS,
and
Swanson LW.
Organization of projections from the dorsomedial nucleus of the hypothalamus: a PHA-L study in the rat.
J Comp Neurol
376:
143-173,
1996[ISI][Medline].
50.
Toth, IE.
Transneuronal labeling of CNS neurons involved in the innervation of the adrenal gland.
Horm Metab Res
30:
329-333,
1998[ISI][Medline].
51.
Tremblay, RR,
Normand M,
and
Fortier C.
[Adrenocortical responses to ACTH (author's transl)].
J Physiol (Paris)
70:
709-715,
1976[Medline].
52.
Vacher, CM,
Fretier P,
Creminon C,
Calas A,
and
Hardin-Pouzet H.
Activation by serotonin and noradrenaline of vasopressin and oxytocin expression in the mouse paraventricular and supraoptic nuclei.
J Neurosci
22:
1513-1522,
2002
53.
Van Dijk, G,
Donahey JC,
Thiele TE,
Scheurink AJ,
Steffens AB,
Wilkinson CW,
Tenenbaum R,
Campfield LA,
Burn P,
Seeley RJ,
and
Woods SC.
Central leptin stimulates corticosterone secretion at the onset of the dark phase.
Diabetes
46:
1911-1914,
1997[Abstract].
54.
Veldhuis, JD,
Iranmanesh A,
Naftolowitz D,
Tatham N,
Cassidy F,
and
Carroll BJ.
Corticotropin secretory dynamics in humans under low glucocorticoid feedback.
J Clin Endocrinol Metab
86:
5554-5563,
2001
55.
Yamashita, H,
Kannan H,
Kasai M,
and
Osaka T.
Decrease in blood pressure by stimulation of the rat hypothalamic paraventricular nucleus with L-glutamate or weak current.
J Auton Nerv Syst
19:
229-234,
1987[ISI][Medline].
56.
Yasuda, Y,
Honda K,
Negoro H,
Higuchi T,
Goto Y,
and
Fukuda S.
The contribution of the median preoptic nucleus to renal sympathetic nerve activity increased by intracerebroventricular injection of hypertonic saline in the rat.
Brain Res
867:
107-114,
2000[ISI][Medline].
57.
Yates, FE,
Russell SM,
Dallman MF,
Hodge GA,
McCann SM,
and
Dhariwal AP.
Potentiation by vasopressin of corticotropin release induced by corticotropin-releasing factor.
Endocrinology
88:
3-15,
1971[ISI][Medline].
58.
Yoshimatsu, H,
Niijima A,
Oomura Y,
Yamabe K,
and
Katafuchi T.
Effects of hypothalamic lesion on pancreatic autonomic nerve activity in the rat.
Brain Res
303:
147-52,
1984[ISI][Medline].
59.
Zaretskaia, MV,
Zaretsky DV,
Shekhar A,
and
DiMicco JA.
Chemical stimulation of the dorsomedial hypothalamus evokes non-shivering thermogenesis in anesthetized rats.
Brain Res
928:
113-125,
2002[ISI][Medline].
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), as well as the control placements
anterior (A) and posterior (P) to the PVN. Each symbol represents an
average placement; the shaded region surrounding the symbol indicates
the extent of all placements on that atlas plate. Numbers indicate the
distance from bregma in mm, according to the atlas of Paxinos and
Watson (
