EFFECTS OF INTRANIGRAL CANNABINOIDS ON ROTATIONAL BEHAVIOR IN RATS - INTERACTIONS WITH THE DOPAMINERGIC SYSTEM

The effect of unilateral intranigral cannabinoid receptor stimulation on rotational behavior was explored. The potent cannabinoid agonist CP 55,940 (5 and 10 mu g/0.5 mu l) induced contralateral turning when mi croinjected unilaterally into the substantia nigra pars reticulata. In addition, the cannabinoid agonist markedly attenuated the contralater al rotation induced by the dopamine D-1 agonist SKF 82958 and complete ly reversed the ipsilateral rotation induced by the dopamine D-2 agoni st quinpirole. In both cases, the coadministration of the cannabinoid agonist together with the D-1 or D-2 agonist induced contralateral rot ation. It appears that cannabinoids may exert different effects depend ing on the state of the ongoing chemical activation of this brain circ uitry.