Clozapine injected into the nucleus accumbens potentiates apomorphine-induced jaw movements

The effects of clozapine injected into the nucleus accumbens on apomorphine-induced jaw movements were studied. Jaw movements induced by apomorphine (0.5 mg/kg i.v.) were potentiated by clozapine (10 micrograms/0.2 microliters) injected into the nucleus accumbens 10 min before apomorphine. Enhancement of the apomorphine-induced jaw movements was also found with the muscarinic acetylcholine receptor antagonist, methylscopolamine (2.5 micrograms), whereas the acetylcholine receptor agonist, carbachol (2.5 micrograms), inhibited the effects of apomorphine. Injection of a smaller dose of carbachol (0.1 microgram) alone into the nucleus accumbens 10 min before failed to alter the effects of apomorphine but prevented the potentiation induced by clozapine. Both the 5-hydroxytryptamine(5-HT)2A receptor antagonist, 2-(2-dimethylaminoethylthio)-3-phenylquinoline hydrochloride (ICI 169,369, 0.1 and 0.2 microgram), and the alpha 1-adrenoceptor antagonist, prazosin (0.05 and 0.2 microgram), failed to affect the effects of apomorphine(0.5 mg/kg i.v.). In contrast, clozapine (1, 5 and 10 micrograms), ICI 169,369 (0.1 and 0.2 microgram) or prazosin (0.05 and 0.2 microgram) given into the ventral striatum inhibited the effects of apomorphine (0.5 mg/kg i.v.). It is suggested that the clozapine-induced potentiation in the nucleus accumbens might be due to its antimuscarinic properties.