Action of endothelin-1 on vasomotor neurons in rat rostral ventrolateral medulla.
Intracisternal administration of endothelin-1 (ET-1) elicits sympathetically mediated cardiovascular responses by acting on the ventral surface of the medulla oblongata (VSM) subjacent to the rostral ventrolateral medulla (RVLM). We examined, in urethane-anesthetized rats, whether intracisternal ET-1 affected activity of vasomotor neurons (VMNs) in the RVLM, by acting either directly on the VMNs or indirectly via the VSM. VMNs were identified electrophysiologically. Intracisternal administration of ET-1 altered activity of all the 13 VMNs tested. At a dose of 0.1 pmol, ET-1 invariably caused transient excitation in six VMNs examined, whereas at a dose of 1 pmol in separate experiments all the seven VMNs tested were inhibited with (n = 6) or without (n = 1) preceding excitation. Similarly, topical application of ET-1 (0.1-1 pmol) to the VSM caused inhibition with (n = 3) or without (n = 2) preceding excitation in all the five VMNs tested. Direct iontophoretic application of ET-1 to the VMNs caused excitation in four of seven VMNs examined but did not affect the other three neurons. These results support the view that intracisternally administered ET-1 alters activity of VMNs in the RVLM, by acting directly on neurons themselves and indirectly via the VSM.
Cao
W H
WH
Department of Physiology, Faculty of Medicine, University of Tokyo, Japan.
Kuwaki
T
T
Unekawa
M
M
Ling
G Y
GY
Terui
N
N
Kumada
M
M
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002946:Cisterna Magna; D004594:Electrophysiology; D016232:Endothelins / Q000008:administration & dosage / Q000494:pharmacology*; D066298:In Vitro Techniques; D007267:Injections; D007478:Iontophoresis; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009046:Motor Neurons / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000294:innervation*; D011311:Pressoreceptors / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D016232:Endothelins