MODIFICATIONS OF HEAD TURNING AND CIRCLING MOVEMENT FOLLOWING SULPIRIDE MICROINJECTIONS INTO NUCLEUS-ACCUMBENS IN THE RAT

The aim of this study was to determine whether a relationship exists b etween nucleus accumbens D-2 receptors, circling behavior, and its fir st stage, the head turning. Rats were unilaterally lesioned in the sub stantia nigra with 6-hydroxydopamine and afterward treated with d-amph etamine IP Following bilateral intraaccumbens microinjections (1, 5, 1 0 mu g/0.5 mu l) of sulpiride, a D-2 receptor antagonist. Computer-ass isted video analysis allowed the study of some parameters (number of t urns, type of turn, head turning duration, degree and speed) character izing rotatory activity. Sulpiride microinfusion resulted in a dose-de pendent decrease of the number of turns and head rotation speed and in a dose-dependent increase of head-turning duration, Two turn types we re observed in relation to the animal's position: a large head-to-tail position with a short-diameter turn type following sulpiride microinj ection, and a close head-to-tail position in relation to a wide diamet er turn type in the control condition (saline). The results show a rel ationship between head turning parameters, circling behavior, and D-2 receptors in nucleus accumbens, which may be also involved in the regu lation of some mechanisms related to sensory-motor integration in the rat.