Inhibitory effect of GABA on firing activity of rostral ventrolateral medullary neurons of rat in vitro.
Extracellular single-unit discharges were obtained from 106 spontaneously active neurons in the region of the rostral ventrolateral medulla (RVLM) by glass microelectrode from 73 brain alices of Sprague-Dawley rats. Exogenous gamma-aminobutyric acid (GABA, 0.1-3.0 mmol/L) inhibited the electrical activity of 84 out of 106 RVLM neurons dose-dependently. The inhibitory effect of GABA could be blocked by GABAA receptor antagonist bicuculline methiodide (BMI) and Cl- channel blocker picrotoxin (PTX). When perfused with BMI or PTX alone, the firing rates of most of the RVLM neurons were significantly increased. In 41 neurons responding to GABA, baclofen (0.1-3.0 mumol/L), a GABAB receptor selective agonist, inhibited the discharges of 33 of the neurons dose-dependently. GABAB receptor antagonist CGP35348 (n = 13) blocked the inhibition due to baclofen (n = 21). After perfused with CGP35348 alone, the firing rates of most of the RVLM neurons were significantly increased. Taken together, the inhibition of GABA on RVLM neurons is mediated through either GABAA or GABAB receptors and some intrinsic GABA neurons exert tonic inhibition activity.
Chu
X P
XP
Department of Physiology, Shanghai Medical University, Shanghai 200032.
Li
P
P
Xu
N S
NS
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D018755:GABA Agonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D066298:In Vitro Techniques; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D018755:GABA Agonists; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D005680:gamma-Aminobutyric Acid; D001418:Baclofen