AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 4 711-R716, Copyright © 1988 by American Physiological Society
Solitary nucleus excitation of supraoptic vasopressin cells via adrenergic afferents
T. A. Day and J. R. Sibbald
Department of Physiology, University of Otago Medical School, Dunedin, New Zealand.
Recent studies confirm that the supraoptic nucleus (SON) receives a direct
projection from the nucleus of the solitary tract (NTS). We have examined
the effect of NTS stimulation on antidromically identified SON
neurosecretory cells that were classified as arginine vasopressin (AVP) or
oxytocin (OXY) secreting in accord with basal activity patterns and
responsiveness to arterial baroreceptor activation. Medial NTS stimulation
at the level of the obex or area postrema excited 78% (59 of 76) of
putative AVP cells (onset latency 52 +/- 1 ms) but only 20% (3 of 15) of
putative OXY cells. Commissural NTS stimulation did not excite AVP cells (n
= 13). After complete SON catecholamine afferent disruption, achieved by
local injection of 6-hydroxydopamine, AVP cells tested were unresponsive to
medial NTS stimulation (12 of 13), although arterial baroreceptor
activation inhibited four of four cells. These data indicate that medial
NTS stimulation preferentially excites SON AVP cells and that this effect
involves an adrenergic input to SON. A direct projection from the A2
catecholamine cell group of the NTS may be involved, although the long
latency to excitation and the poor correspondence between effective NTS
stimulation sites and the location of the A2 group within NTS raise the
possibility that a relay projection, possibly through the A1 catecholamine
cell group of the ventrolateral medulla, may be involved.
