ABSTRACT
Beta-carboline alkaloids, also known as harmala's alkaloids have a wide spectrum of pharmacological actions including a stimulatory action on release of dopamine and other catecholamines in several brain regions and an inhibitory action on monoamine oxidase [MAO]. These findings suggest that beta-carbolines should alleviate at least some of the dopaminergic stereotyped behaviors. The purpose of present study is to determine the effects of beta-carbolines harmane, norharmane and harmine on apomorphine-induced pecking behavior in chick. All experiments were carried out on male/female chicks [40-60 g]. The modulatory effects of beta-Carbolines on stereotyped behavior were assessed using the pecking behavior induced by apomorphine. Subcutaneous [s.c.] injection of apomorphaine [0.025 mg/kg, mixed agonist of dopamine D1/D2 receptors] induced pecking. The pecking response was counted by direct observation and recorded for a 40-minute period. S.C. injection of harmane [2.5-10 mg/kg] and harmine [1.25-5 mg/kg] significantly decreased the pecking behavior induced by apomorphine [0.25 mg/kg]. The norharmane [2.5-15 mg/kg, i.p.] response was biphasic. The inhibitory effects of harmane, norharmane and harmine were blocked by flumazenil [5 mg/kg, i.e., 30 minutes before the test] or reserpine [5 mg/kg, i.e., 18 hours before the test]. Results suggest that the modulatory effect of harmane, norharmane and harmine on the pecking behavior may be mediated through an inverse agonistic/monoaminergic mechanism