Effects of GABAergic system on naloxone-induced jumping in morphine-dependent mice

Abstract

The effect of GABA (γ-aminobutyric acid system) receptor agonists and antagonists on naloxone-induced jumping in morphine-dependent mice was examined. Intraperitoneal (i.p.) or intracerebroventricular (i.c.v.) injection of different doses of the GABA B receptor agonist, baclofen (2.5, 5 and 10 mg/kg), reduced naloxone-induced jumping in morphine-dependent mice. The i.p. administration of the GABA B receptor antagonist, CGP35348 ( P-[3-aminopropyl]- p-diethoxymethyl-phosphinic acid), but not the i.c.v. injection of the drug, increased naloxone-induced jumping. The antagonist also decreased the baclofen response. Administration of the GABA A receptor agonist, muscimol, but not the GABA A receptor antagonists bicuculline and picrotoxin, decreased the naloxone response in morphine-dependent animals. It is concluded that both GABA A and GABA B receptor subtypes may have an inhibitory influence on naloxone-induced withdrawal jumping in mice.