THE ATTENUATION OF SCHEDULE-INDUCED-POLYDIPSIA BY DOPAMINE BLOCKERS IS NOT AN EXPRESSION OF EXTRAPYRAMIDAL SIDE-EFFECT LIABILITY

The effects of scopolamine and diazepam on attenuation of schedule-ind uced polydipsia (SIP) produced by a dopamine D1 antagonist, SCH 23390, a dopamine D2 antagonist, raclopride, and a mixed D1/D2 antagonist, c is(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 or flupentixol. Diazepam reversed the effect of flupentixol, suppressed the reversal of the SC H 23390-treated group to control level after withdrawal, and was witho ut effect on the raclopride-treated group. It is concluded that the su ppression of SIP behaviour induced by the dopamine blockers is not due to the induction of extrapyramidal side effects. However, it cannot b e excluded that the effects of SCH 23390 and flupentixol may be mediat ed through the motoric dopamine system, as they inhibited the initiati on of drinking behaviour.