Decortication decreases paired-pulse facilitation in the neostriatal slice of the rat.

Paired-pulse facilitation, a form of short-term synaptic enhancement, occurs in the neostriatum. The present experiments were designed to determine the contributions of neostriatal afferents to the maintenance of this form of short-term facilitation. There are 3 major afferents to the neostriatum: the neocortex, the substantia nigra and the medial thalamus. Since the largest inputs into the neostriatum emanate from the neocortex and substantia nigra, the effects of unilateral decortication or unilateral dopamine depletion on paired-pulse facilitation were primarily examined. Intracellular recordings were made from neostriatal neurons in brain slices 2 weeks following unilateral decortication or dopamine-depleting lesions. Statistically significant decreases in paired-pulse facilitation of the synaptic response evoked by local stimulation occurred only after neocortical damage. In contrast, paired-pulse facilitation in neostriatal neurons ipsilateral to the dopamine depleting lesion was not significantly altered. These results indicate that the corticostriatal input is primarily responsible for neostriatal short-term synaptic facilitation.