Involvement of dopaminergic neurotransmission in the control of goal-directed movements

Changes produced in dopamine (DA) activity, by administration of the DA-antagonists metoclopramide (10 mg/kg IM) and tiapride (16 mg/kg IM) and of the DA agonists apomorphine (0.5 and 1 mg/kg IM) and bromocriptine (8 mg/kg orally), specifically modified predatory behavior in the ferret. Sulpiride (40 mg/kg IP and 90 mg/kg IM) did not change the behavior. The number of bites necessary to kill the prey was reduced by metoclopramide and tiapride. The number of bites after the death of the prey was not changed. The latency from the first bite to the death of the prey was shortened. Apomorphine and bromocriptine increased the number of bites.The DA receptor blockers haloperidol, chlorpromazine, and clozapine had similar effects to metoclopramide and tiapride, and the DA agonist l-dopa had similar effects to apomorphine and bromocriptine. The pattern of results indicated that, considering the two major DA receptor types, D-2 receptors or D-2 in combination with D-1 but not D-1 receptors alone were involved in the control of goal-directed movements. The results also provided some evidence that blockade of these DA receptors caused a narrowing of the range of exhibited behavioral responses. Stimulation of these DA receptors had opposite effects.