Electrophysiological and behavioral effects of neurotensin in rat globus pallidus: an in vivo study.

The globus pallidus plays a critical role in movement regulation. Morphological study has indicated that the globus pallidus receives neurotensinergic innervation from the striatum. The present study investigated the effects of activating neurotensin receptor in globus pallidus. In vivo single unit electrophysiological recordings showed that micro-pressure ejection of neurotensin into the globus pallidus increased spontaneous firing of pallidal neurons. The excitatory effect of neurotensin could be mimicked by the C-terminal fragment, neurotensin (8-13), but not by the N-terminal fragment, neurotensin (1-8). Local administration of both the non-selective neurotensin receptor antagonist, SR142948A, and the selective neurotensin type-1 receptor antagonist, SR48692, blocked the excitatory effect induced by neurotensin. In the behaving rats, we observed the postural effects of neurotensin in the globus pallidus. Unilateral microinjection of neurotensin into the globus pallidus induced a SR48692-sensitive contralateral dystonic posturing in the presence of systemic haloperidol administration, which could be accounted for by the electrophysiological effect of neurotensin in increasing the firing rate of pallidal neurons. Our in vivo electrophysiological and behavioral findings suggest that pallidal neurotensin receptor plays a role in the basal ganglia motor circuit by mediating an excitation of spontaneous activity in the globus pallidus.