Effects of diazepam and muscimol on GABA-mediated neurotransmission: interactions with inosine and nicotinamide.

Inosine and nicotinamide have been proposed as endogenous ligands for the brain benzodiazepine receptor. An $\text{in vivo}$ method for detecting drugs with GABA-mimetic properties was used to examine the effects of inosine, nicotinamide and diazepam in the rat globus pallidus. Inosine and nicotinamide completely prevented the GABA-mimetic action of diazepam but neither compound alone had any GABA-like activity. These findings suggest that inosine and nicotinamide are able to antagonize but are not able to mimic the GABA-like actions of diazepam at the benzodiazepine receptor.