AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 5 934-R940, Copyright © 1986 by American Physiological Society
Caudolateral areas of medulla-mediating release of ACTH in cats
D. A. Bereiter and D. S. Gann
The effect of electrical stimulation of the caudolateral brain stem on
plasma adrenocorticotropin (ACTH) was assessed in cats anesthetized with
alpha-chloralose-urethan. To examine the influence of stimulus pattern on
ACTH release, an equal number of pulses was presented in a continuous
pattern and in a burst pattern at each electrode site. Stimulation of the
magnocellular portion (layers 4-6) of trigeminal nucleus caudalis evoked a
significant (P less than 0.01) and equal peak change in plasma ACTH after
continuous pattern (+121 +/- 32 pg/ml) and after burst pattern stimuli
(+126 +/- 30 pg/ml, n = 21). In contrast, stimulation of more ventromedial
portions (layers 7-8) of nucleus caudalis had no significant effect on
plasma ACTH. Stimulation of the trigeminal lateral cervical region the
caudal extent of the A1 noradrenergic cell group, or the lateral reticular
nucleus evoked significant peak increases in plasma ACTH regardless of
stimulus pattern. Transient changes in arterial pressure accompanied brain
stem stimulation and were not correlated with the changes in ACTH. The
results indicate that stimulation of trigeminal subnucleus caudalis, a
brain stem region that processes nociceptor afferent information, evokes a
prompt increase in plasma ACTH. Stimulation of brain stem regions that
process autonomic and cardiovascular afferent information (A1 region,
lateral reticular nucleus) also facilitate ACTH release. No significant
influence of stimulus pattern on brain stem-evoked ACTH release was seen.
The results support the hypothesis that the influence of the central
nervous system on ACTH release may be processed by parallel pathways at the
caudal brain stem level.
