Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 40 2 2002 06 15 109 114 Bagheri T Ejtemaei Mehr Sh Shamshirgaran Sh 2015 09 28 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 dose- dependent 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 peking (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 Li+ can modulate dopamine and serotonin function by different mechanisms and decrease this effect. As a result, it is 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. https://acta.tums.ac.ir/index.php/acta/article/view/2592 https://acta.tums.ac.ir/index.php/acta/article/download/2592/2575