Comparative study on pharmacological properties of sultopride, sulpiride and other antipsychotic drugs: Influences of sultopride, sulpiride and other antipsychotic drugs on the changes in locomotor activity induced by apomorphine in mice

Abstract In order to elucidate pharmacological properties of sultopride and sulpiride, their effects on the locomotor hyperactivity induced by apomorphine in mice were examined by use of photo-cell method and compared with those of other antipsychotic drugs. Apomorphine was injected subcutaneously to mice 30 min after i.p. injection of test drugs: sultopride(SLT), sulpiride (SLP), chlorpromazine (CPZ), haloperidol (HPD), pimozide (PMZ), imipramine (IMP) and yohimbine(YOH). Apomorphine(1 mg/kg) induced a significant and marked increase in a locomotor activity in mice. SLT potentiated the apomorphine-induced locomotor activity at small doses(0.1-3 mg/kg), but inhibited at a dose of 30 mg/kg. SLP(0.3-30 mg/kg) also potentiated significantly the apomorphine response,but did not inhibit the response at even a high dose(100 mg/kg). CPZ(3-10 mg/kg) and HPD(0.3 mg/kg) markedly inhibited the apomorphine response. On the other hand, PMZ induced a significant potentiation on the apomorphine response at small doses(0.1-0.3 mg/kg) and significant inhibition at a dose of 3 mg/kg. IMP(10 mg/kg) also induced a significant potentiation on the apcmorphine response. YOH(0.3-10 mg/kg) did not represent extreme influence on the apomorphine response. These results suggested that the potentiation of the apomorphine-induced locomotor hyperactivity by SLT, SLP, PMZ, and IMP might reflect disinhibitory effect of these drugs The mechanism of the disinhibitory effect of these drugs might be due to the blockade of the presynaptic dopamine receptors; however,the possibility of the participation of noradrenergic systems was not excluded.