The role of GABAB receptors in mediating the stimulatory effects of ethanol in mice.

Recently, the GABAB receptor antagonist phaclofen has been shown to attenuate the stimulation of locomotor activity induced by ethanol (Allan and Harris 1989). In the present study, the effects of a range of recently developed GABAB receptor antagonists (phaclofen, 2-hydroxysaclofen, beta-phenyl-beta-alanine, CGP 35348) and the GABAB receptor agonist baclofen, were studied for their ability to block the locomotor stimulation induced by a low dose of ethanol administered IP to mice (1.75 g/kg). Results showed that phaclofen, 2-hydroxysaclofen, BPBA and baclofen all dose-dependently decreased ethanol-induced locomotor activity, and, of these, baclofen and BPBA did so at doses which did not attenuate locomotor activity when administered alone. CGP 35348 had no effect on the activity produced by ethanol. The action of baclofen on ethanol-induced activity appeared to be GABAB receptor mediated, as the effects were stereospecific and were reversed by the antagonist, CGP 35348. However phaclofen, 2-hydroxysaclofen and BPBA failed to reverse the effects of baclofen. These results suggest that the GABAB receptor may modulate locomotor stimulation induced by low doses of ethanol, and furthermore, that agonist, rather than antagonist activity at the GABAB receptor is responsible for this reduction. The GABAB receptor subtype responsible for modulating the effects of ethanol may have properties different from those GABAB receptors characterised to date.