Open AccessLocalization of [125I]Endothelin Binding Sites in the Region of the Carotid Bifurcation and Brainstem of the Cat
Author(s) -
K. M. Spyer,
Daniel S. McQueen,
M Dashwood,
R. M. Sykes,
M. de Burgh Daly,
J. R. Muddle
Publication year - 1991
Publication title -
journal of cardiovascular pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.762
H-Index - 100
eISSN - 1533-4023
pISSN - 0160-2446
DOI - 10.1097/00005344-199100177-00108
Subject(s) - baroreceptor , chemoreceptor , carotid sinus , carotid body , endocrinology , endothelin receptor , medicine , brainstem , chemistry , reflex , anesthesia , blood pressure , anatomy , heart rate , electrophysiology , receptor
We have demonstrated by autoradiography, displaceable binding for [125I]endothelin-1 ([125I]ET-1), [125I]endothelin-2 ([125I]ET-2), and [125I]endothelin-3 ([125I]ET-3) in the cat carotid bifurcation as well as in the nucleus of the tractus solitarius, where baroreceptor and chemoreceptor afferents from the carotid body and sinus terminate. There was also significant binding in the nodose and superior cervical ganglia. Barosensory and chemosensory discharge was recorded from filaments of the carotid sinus nerve in cats anesthetized with pentobarbitone. Intra-carotid injection of ET-1 or ET-3 (4-402 pmoles) caused transient dose-related depression of baroreceptor discharge without any immediate effects on systemic blood pressure (BP) or heart rate; there was a delayed biphasic effect on BP. ET-1 had little effect on chemosensory discharge during the first 15 s post-injection, but there was a delayed (45-90 s) dose-related increase in discharge. The effects of all three ETs were qualitatively similar, and ET enhanced chemoexcitation evoked by either acetylcholine or sodium cyanide. Our results show that (a) ET binding sites are located in the baroreceptor and chemoreceptor afferent pathways and (b) ETs can influence afferent activity of baroreceptors and chemoreceptors. Further studies are needed to determine the significance of these findings, particularly with regard to reflex control of the cardiovascular system.