Neurotensin depolarizes globus pallidus neurons in rats via neurotensin type-1 receptor

The globus pallidus is a major component in the indirect pathway of the basal ganglia. There is evidence that neurotensin receptors exist in this nucleus. To determine the electrophysiological effects of neurotensin on pallidal neurons, whole-cell patch-clamp recordings were performed in the acutely prepared brain slices. Under current-clamp recordings, neurotensin at 1 μM depolarized pallidal neurons. Voltage-clamp recordings also showed an inward current induced by neurotensin. The depolarizing effect of neurotensin could be mimicked by the C-terminal fragment, neurotensin (8-13), but not by the N-terminal fragment, neurotensin (1-8). Both SR 142948A, a non-selective neurotensin receptor type-1 and type-2 antagonist, and SR 48692, a selective type-1 receptor antagonist, blocked the depolarizing effect of neurotensin, and which themselves had no effect on membrane potential. Thus, neurotensin type-1 receptors appear to mediate the effect of neurotensin. The depolarization evoked by neurotensin persisted in the presence of tetrodotoxin, ionotropic and metabotropic glutamate and GABA receptor antagonists, indicating that neurotensin excited the pallidal neurons by activating the receptor expressed on the neurons recorded. Current-voltage relationship revealed that both the suppression of a potassium conductance and the activation of a cationic conductance are involved in the neurotensin-induced depolarization. Based on the action of neurotensin in the globus pallidus we hypothesize that alterations of the striatopallidal neurotensin system contribute to symptoms of basal ganglia motor disorders.