EFFECT OF CLOZAPINE UPON SCHEDULE-INDUCED-POLYDIPSIA (SIP) RESEMBLES NEITHER THE ACTIONS OF DOPAMINE D1 NOR D2 BLOCKADE

The effects of clozapine (CLOZ) upon acquired schedule-induced polydip sia in rats were compared to the effects of the dopamine (DA) D-1 anta gonist SCH 23390 (SCH) and the DA D-2 antagonist raclopride (RAC). Ah three compounds suppressed water consumption, but only SCH and RAC dec reased drinking efficiency. SCH was the only compound with an effect o n panel pressing (PP), causing suppression even at a dose without effe ct upon water intake. SCH also affected the temporal pattern of lickin g (TPL) at all doses, while clozapine, 10 mg/kg, only affected the pat tern acutely, and raclopride was without effect. In conclusion, PP and the TPL are more sensitive to D-1 than D-2 blockade. While PP and the TPL are more sensitive than water intake to D-1 blockade, the opposit e is true for D-2 blockade. It is possible to differentiate between DA D-1/D-2 antagonists and CLOZ in this model, focusing upon reduction i n water consumption, with and without reduction in drinking efficiency . Furthermore, it is possible to differentiate between D-1 and D-2 blo ckade by analyzing water consumption, PP and the TPL.