THE EFFECT OF ACUTE LITHIUM AND RUBIDIUM PRETREATMENT ON APOMORPHINE-INDUCED PECKING IN PIGEONS

The effects of different doses of lithium (5-320 mg/kg intramuscularly ) and rubidium (0.25-32 mg/kg intramuscularly) on apomorphine-induced pecking were investigated in pigeons. These two cations did not induce pecking by itself. Intramuscular administration of apomorphine (a mix ed D1/D2 dopamine receptors agonist, 0.1-1.6 mg/kg) induced pecking in a dose-dependent manner. SCH 23390 (D1 dopamine receptor antagonist, 0.02-0.08 mg/kg) and sulpiride (D2 dopamine receptor antagonist, 25-10 0 mg/kg) decreased apomorphine-induced pecking dose-dependently. Combi nation of SCH 23390 (0.04 mg/kg) with sulpiride (50 mg/kg) caused a st ronger inhibitory effect on apomorphine response. This indicates that both D1 and D2 dopamine receptors are involved in apomorphine-induced pecking. The response induced by apomorphine (0.2-0.8 mg/kg) was decre ased in animals pretreated with lithium and rubidium. In these conditi ons, SCH 23390 and sulpiride produced a larger inhibitory effect on th e apomorphine response, suggesting that acute lithium and rubidium pre treatment inhibit pecking by interfering with dopaminergic mechanisms.