HEMISPHERIC ASYMMETRIES IN SPONTANEOUS FIRING CHARACTERISTICS OF SUBSTANTIA-NIGRA PARS RETICULATA NEURONS FOLLOWING A UNILATERAL 6-HYDROXYDOPAMINE LESION OF THE RAT NIGROSTRIATAL PATHWAY

Single unit activity of substantia nigra pars reticulata (SNR) neurons was recorded bilaterally in rats subjected to unilateral 6-hydroxydop amine lesions of the ascending mesostriatal dopaminergic pathway, resu lting in an almost complete loss of dopaminergic neurons in the ipsila teral SN pars compacta. Firing rate and firing pattern of SNR neurons in lesioned rats were compared with respective data from sham-lesioned rats and naive controls. In lesioned rats, the mean firing sate of SN R neurons at the lesioned side was significantly reduced and there was an increase in the occurrence of bursting activity. In contrast, firi ng rate in the contralateral SNR was significantly increased; without change in the frequency of bursting neurons. This asymmetrical change in spontaneous firing characteristics of SNR neurons following the les ion could be involved in the complex behavioral changes seen in this m odel of Parkinson's disease. (C) 1997 Elsevier Science B.V.