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Title: Midline medullary depressor responses are mediated by inhibition of RVLM sympathoexcitatory neurons in rats.
Austin Authors: Verberne, Anthony J M ;Sartor, Daniela M;Berke, A
Affiliation: University of Melbourne, Clinical Pharmacology and Therapeutics Unit, Austin and Repatriation Medical Centre, Heidelberg, Victoria 3084, Australia
Issue Date: 1-Apr-1999
Publication information: The American Journal of Physiology; 276(4 Pt 2): R1054-62
Abstract: Mechanisms underlying the depressor and sympathoinhibitory responses evoked from the caudal medullary raphe (MR) region were investigated in pentobarbital sodium-anesthetized, paralyzed rats. Intermittent electrical stimulation (0.5 Hz, 0.5-ms pulses, 200 microA) of the MR elicited a mixed sympathetic response that consisted of a long-latency sympathoexcitatory (SE) peak (onset = 146 +/- 7 ms) superimposed on an inhibitory phase (onset = 59 +/- 10 ms). Chemical stimulation of the MR (glutamate; Glu) most frequently elicited depressor responses accompanied by inhibition of sympathetic nerve discharge. Occasionally, these responses were preceded by transient pressor and SE responses. We examined the influence of intermittent electrical stimulation (0.5 Hz, 0.5-ms pulses, 25-200 microA) and Glu stimulation of the MR on the discharge of rostral ventrolateral medulla (RVLM) premotor SE neurons. Peristimulus-time histograms of RVLM unit discharge featured a prominent inhibitory phase in response to MR stimulation (onset = 20 +/- 2 ms; duration = 42 +/- 4 ms; n = 12 units). Glu stimulation of the MR reduced blood pressure (-37 +/- 2 mmHg, n = 19) and inhibited the discharge of RVLM SE neurons (15 of 19 neurons). Depressor and sympathoinhibitory responses elicited by chemical and electrical stimulation of the MR region are mediated by inhibition of RVLM premotor SE neurons and withdrawal of sympathetic vasomotor discharge.
Gov't Doc #: 10198385
Type: Journal Article
Subjects: Animals
Blood Pressure.physiology
Electric Stimulation
Glutamic Acid.pharmacology
Lumbosacral Region
Medulla Oblongata.drug effects.physiology
Neural Inhibition.physiology
Raphe Nuclei.drug effects.physiology
Rats, Sprague-Dawley
Sympathetic Nervous System.cytology.physiology
Appears in Collections:Journal articles

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