The attenuation of schedule-induced polydipsia by dopamine blockers is not an expression of extrapyramidal side...

The effects of scopolamine and diazepam on attenuation of schedule-induced polydipsia (SIP) produced by a dopamine D1 antagonist, SCH 23390, a dopamine D2 antagonist, raclopride, and a mixed D1/D2 antagonist, cis(Z)-flupentixol, were examined in a chronic dose regime, followed by 7 days of withdrawal. Scopolamine potentiated the effect of SCH 23390, but did not alter the effects of raclopride of flupentixol. Diazepam reversed the effect of flupentixol, suppressed the reversal of the SCH 23390-treated group to control level after withdrawal, and was without effect of the raclopride-treated group. It is concluded that the suppression of SIP behaviour induced by the dopamine blockers is not due to the induction of extrapyramidal side effects. However, it cannot be excluded that the effects of SCH 23390 and flupentixol may be mediated through the motoric dopamine system, as they inhibited the initiation of drinking behaviour.