Effects of lithium carbonate on apomorphine-induced sniffing behaviour in rats

Therapeutic effects of lithium in manic-depressive disorders have been clarified. During the present study, the effects of lithium carbonate have been assessed on apomorphine-induced sniffing in rats. Male albino rats were housed in a glass cylinder and food and water were freely available till 60 minutes before the experiment. Immediately after apomorphine injection the sniffing behaviour was observed directly for 60 minutes. Sniffing was scored every 15 seconds. According to the following scale: 0=absent, 1=sniffing. Intraperitoneal (IP) administration of different doses of apomorphine (0.25,0.5 and 1mg/kg) induced a dose-dependent sniffing response. Chronic lithium carbonate exposure (0.1% in drinking water for 30-35 days) but not acute administration of the drug (320 mg/kg, IP) decreased the response of apomorphine. Administartion of D1 dopamine receptor antagonist,SCH-23390 (0.01mg/kg, IP) or the D2 dopamine receptor antagonist, sulpiride (25mg/kg, IP) did not accompany alteration in apomorphine response in rats treated with acute lithium carbonate. In animals treated chronically with lithium carbonate the blockade of apomorphine response by sulpiride but not SCH23390 was potentiated. It is concluded that chronic treatment of animals with lithium carbonate is able to alter D2 dopamine receptors response.