TURNING BEHAVIOR IN RATS WITH UNILATERAL LESION OF THE SUBTHALAMIC NUCLEUS - SYNERGISM BETWEEN D1 AND D2 RECEPTORS

Rats with unilateral kainic acid lesion of the subthalamic nucleus sho wed a dose dependent rotational response to the lesioned side (ipsilat eral) after systemic administration of the non-selective dopaminergic agonist apomorphine. Both D2 and D1 selective antagonists ((-)sulpirid e and SCH23390) inhibited the response to apomorphine in these rats, S elective D2 and D1 agonists (quinpirole and SKF38393) were unable to i nduce turning behavior. However, an ipsilateral circling response was obtained after the simultaneous application of both agonists. The inte raction mechanism between dopaminergic receptor subtypes seems to be s imilar to that of other normosensitive models of turning previously st udied (Barone et al., 1986; Robertson and Robertson, 1986; Amt and Per regard, 1987; Asim et al., 1990; Pazo et al., 1993). It is proposed th at the ipsilateral turning response to dopaminergic agonists in rats w ith subthalamic nucleus lesion results from an impaired behavioral exp ression of the action of dopaminergic agonists on one side, leading th e rats to turn away from the intact hemisphere.