Biphasic dose-response effect of baclofen on haloperidol catalepsy in the rat

Haloperidol-induced catalepsy in rats is reduced by low dose baclofen and is potentiated by high dose baclofen. This biphasic behavioral effect is consistent with reported differences between presynaptic and postsynaptic GABA receptors. Low dose baclofen could have an anti-cholinergic effect by activating presynaptic GABA receptors that inhibit the release of acetylcholine. High dose baclofen could have an anti-dopamine effect by activating postsynaptic GABA receptors that inhibit the firing of dopamine neurons.