Denervation-like postsynaptic supersensitivity to dopamine agonists induced by microinjection of colchicine into the substantia nigra pars compacta.

Circling behavior induced by dopamine (DA) agonists following microinjection of colchicine or 6-hydroxydopamine (6-OHDA) into the substantia nigra pars compacta (SNC) or electrolytic lesions of the SNC was investigated. Methamphetamine produced a contralateral circling behavior 3, 7 and 14 days following injection of colchicine into the SNC. Apomorphine produced an ipsilateral circling behavior followed by a contralateral rotation 3 and 7 days after the infusion of colchicine, whereas only an ipsilateral circling behavior was produced by apomorphine on day 14. 6-OHDA lesions of the SNC produced a contralateral circling behavior to apomorphine and an ipsilateral circling to methamphetamine, whereas both apomorphine and methamphetamine induced ipsilateral circling behaviors in rats with electrolytic lesions of the SNC. The possible mechanisms of action of colchicine are discussed in relation to the known effects of colchicine on axoplasmic transport.