Changes in substantia nigra pars reticulata activity following lesions of the substantia nigra pars compacta

Single unit activity of substantia nigra reticulata (SNr) neurons was recorded in normal rats and bilaterally in rats subjected to a unilateral 6-hydroxydopamine lesion of the substantia nigra compacta 2-4 weeks previously. Lesions were assessed by rotational behaviour to apomorphine. In normal rats the majority of neurons (63%) showed a regular firing pattern. Following lesion the percentage of these cells was similar in the SNr contralateral to the lesion but decreased on the lesioned side to 26%, whereas bursting activity developed (37% vs 5% in normal rats). The mean firing rate of reticulata neurons was slightly increased after lesion, but not statistically significant.