ASYMMETRICAL ORIENTATION TO EDGES OF AN OPENFIELD - MODULATION BY STRIATAL DOPAMINE AND RELATIONSHIP TO MOTOR ASYMMETRIES IN THE RAT

Rats with unilateral 6-hydroxydopamine (6-OHDA, 4 or 8 mu g) or sham l esions of the substantia nigra were examined (undrugged) for asymmetri cal orientation to edges of a large openfield. Lesioned rats preferent ially aligned with the edge such that the intact striatum was contrala teral to the edge. The magnitude of this asymmetry was greatest in rat s lesioned with the highest dose of 6-OHDA. There was no population le ft/right hemispheric asymmetry in the extent to which unilateral stria tal dopamine (DA) depletion produces this behavioral bias. In sham-les ioned rats, endogenous imbalances in striatal DA activity (DOPAC/DA) w ere related to the direction of edge orientation, such that the more a ctive striatum tended to be contralateral to the edge. Also in shams, the direction of this orientational asymmetry was not significantly re lated to the direction of motor bias measured as amphetamine- and apom orphine-induced turning behavior in rotometers (having no edges). Howe ver, the magnitudes of sensorimotor (edge behavior) and motor (turning ) asymmetries were negatively correlated. The results extend previous findings that asymmetrical edge behavior is a sensitive index of imbal ances in striatal DA activity, not only in DA-depleted rats, but in in tact rats as well. Furthermore, sensorimotor and motor asymmetries, wh ile both under DAergic influence, are largely independent processes.