The neurotensin analog xenopsin excites nigral dopamine neurons

The electrophysiological effects of neurotensin (NT), its analog xenopsin, and the fragment NT-(1-8) on the activity of dopaminergic neurons in rat substantia nigra slices were compared. Xenopsin and NT produced a concentration-dependent increase in the firing rate. The mean firing rate was increased by 58.5% with xenopsin (0.1 microM) and 49.1% with NT (0.1 microM). NT-(1-8) was inactive at this concentration. Dopamine (100 microM) inhibited firing in these neurons by 54.7%. These data provide evidence that xenopsin mimics the physiological effects of NT.