The Effect of Acute Lithium and Ami-193, a New 5ht2 Antagonist, on Apomorphine-induced Pecking in Pigeon

Intramascular (IM) administration of apomorphine ( a mixed D1/D2 dopamine receptors agonist ,0.2-1.6 mg/kg ) induced pecking,a stereotype behavior in pigeons in a dosedependent manner. In this study the effect of lithium (Li, 240 mg/kg, IM) and AMI-193(a new 5-HT2 antagonist, 0.003 mg/pigeon) on apomorphine-induced pecking (AIP) were investigated. This study showed that Li and AMI-193 did not induce pecking by itself but administration of each of these agents before apomorphine increased and decreased the AIP (apomor-phine 0.8 mg/kg) respectively whereas concomitant use of Li(240 mg/kg IM) and AMI-193 decreased AIP significantly.These results suggested that 5-HT2 antagonists inhibit the inhibitory effect of serotonin on the dopamine release in the raphe-striatal pathway but Lican modulate dopamine and serotonin function by different mechanisms and decrease this effect. As a result, it is concluded serotonin can decrease the AIP through 5-HT2 receptors indirectly by decrease the dopamine release. Acta Medica Iranica: 40 (2): 109-114; 2002