Impairment of responses to novelty by apomorphine and its antagonism by neuroleptics in mice.

The effects of several doses of apomorphine (AP: 0.062-8 mg/kg) on novelty preference (NP) in male Swiss mice were studied. AP induced a dose-dependent reduction of NP as well as of locomotor activity. The decrease in NP appeared to be related to the effect of the drug in reducing locomotion, and may be explained by a drug-induced increase in perseverance and stereotypy interfering with locomotion and NP by response incompatibility. These results contrast with those obtained with methamphetamine (MA) in a previous study (Misslin and Ropartz 1981) replicated here which also shows a reduction of NP. Furthermore, the neuroleptic thioridazine did not antagonize the effects of AP or MA on NP in mice, whereas the substituted benzamides tiapride and sulpiride did so. The substituted benzamides appear to act selectively on a restricted dopamine receptor population.