Cardiovascular influences on rat parabrachial nucleus: an electrophysiological study.
The rat pontine parabrachial nucleus is a prominent recipient of autonomic-related information from the more caudal levels of the neuraxis. The present experiments examined the responsiveness of neurons within the parabrachial nucleus to the following three specific cardiovascular stimuli: the activation of peripheral arterial baroreceptors, right atrial stretch receptors, and the administration of systemic angiotensin (ANG) II. Extracellular recordings in urethan-anesthetized animals indicate the presence of cells, mostly within the lateral parabrachial nucleus, that increase (17.5%, 28 of 160 cells) and decrease (48.1%, 77 of 160 cells) their excitability consequent to baroreceptor activation. A similar profile of alteration in cellular firing rates was observed with intravenous ANG II (increase in 15.8%, 16 of 101 cells; decrease in 28.7%, 29 of 101 cells). In contrast, fewer neurons located within the medial parabrachial and the Kölliker-Fuse nuclei were activated by these stimuli. A majority of cells (80%, n = 15) displayed a lack of response to right atrial stretch receptor activation. Of ANG II-sensitive lateral parabrachial cells, 23% (n = 43) revealed an alteration in excitability that could not be explained on the basis of a response to elevation in blood pressure. It is possible that this group of cells may be activated by the actions of systemic ANG II on neurons of the area postrema, a circumventricular structure, whose central projections are directed toward the parabrachial nucleus. These findings also support the notion of a diversity of cardiovascular inputs to topographically segregated regions within the parabrachial nucleus.
Jhamandas
J H
JH
Department of Medicine, Faculty of Medicine, University of Alberta, Edmonton, Canada.
Aippersbach
S E
SE
Harris
K H
KH
D000804:Angiotensin II / Q000502:physiology; D000818:Animals; D016275:Atrial Function; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D004553:Electric Conductivity / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D006325:Heart Atria / Q000648:ultrastructure; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D011149:Pons / Q000166:cytology / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D000804:Angiotensin II