Kindling of dopaminergic pathways modifies the effect of substantia nigra lesions on rotational behaviour

Recent studies in rats have implicated a crossed nigrostriatal (NS) pathway in the behavioural recovery that may follow unilateral lesions of the substantia nigra pars compacta (SNc). In the present study, cerebral dominance was determined from the rat's preferred direction of amphetamine-induced rotation. The ventral mesencephalic area giving rise to the crossed nigrostriatal pathway was then kindled either in the dominant hemisphere (in half of the rats), or in the non-dominant hemisphere (in the rest). All rats were then given 6-hydroxydopamine lesions in the lateral portion of the SNc on the dominant side. In control groups, the kindling procedure or electrode implantation was omitted. Neither kindling alone nor the lesion alone was found to alter the direction of amphetamine-induced rotation. In combination, however, kindling in the dominant hemisphere followed by lesioning of the lateral SNc in the dominant hemisphere caused a significant shift in the direction of rotation. This finding can be interpreted in terms of a long-term potentiation of the crossed nigrostriatal pathway after kindling. It is suggested that partial deafferentation of the neostriatum in the dominant hemisphere, combined with enhanced cross-innervation of the contralateral system, led to a shift of cerebral dominance to the intact side.