Electrophysiological characterization of rat striatal neurons in vitro following a unilateral lesion of dopamine cells.

The effects of a unilateral 6 to 19-week lesion of dopamine cells on the excitability of rat striatal neurons were investigated in vitro using the intracellularly recorded membrane properties of neurons obtained ipsilateral and contralateral to 6-hydroxydopamine (6-OHDA) injection sites. Neurons ipsilateral to the lesion site and in striatal tissue depleted of dopamine exhibited resting membrane potentials and membrane resistances similar to those recorded in contralateral striatal neurons. Denervation appeared to have no appreciable effect on the proportion of neurons exhibiting various patterns of neuronal spiking (repetitive, bursting, or single spike) evoked by depolarizing current pulses. Current-voltage determinations revealed nominal rectification in the majority of neurons and marked nonlinearity consistent with inward rectification at potentials hyperpolarized and depolarized to rest in a large proportion of the remaining neurons. Neurons ipsilateral to 6-OHDA lesion sites exhibited these relationships in the same proportion as contralateral control cells. However, ipsilateral neurons with nominal rectification exhibited an average rate constant for the early onset of small hyperpolarizing membrane transients which was significantly smaller than that of controls. This finding suggests that intrinsic membrane parameters regulating the excitability of certain striatal neurons may be under the influence of dopamine or other factors closely associated with nigrostriatal nerve terminals.