Asymmetrical distribution of neurotensin immunoreactivity following unilateral injection of 6-hydroxydopamine in rat ventral tegmental area (VTA).

Intraperitoneal administration of haloperidol (HAL) is reported to be followed within 24 h by increases in the numbers of NT-IR neurons selectively in the ventral striatum. We now report a similar but more dramatic response following unilateral 6-hydroxydopamine (6-OHDA) injections in the ventral tegmental area (VTA). Three days following such injections, NT-IR neurons were more numerous in striatal districts on the lesioned as compared to unlesioned sides of the brains. In contrast to conditions following DA receptor blockade, the distribution of NT-IR neurons extended to include dorsal striatal territories after 6-OHDA lesions, including the extreme dorsolateral quadrant, which in all previous studies has been reported devoid of NT-IR neurons. The moderate expansion of the NT-IR pallidal districts observed after HAL treatment was more pronounced after 6-OHDA. The NT-IR territory of the globus pallidus on the lesioned side was markedly larger than its counterpart on the unlesioned side. Lateral ventral pallidum, which gives rise to projections terminating in the substantia nigra and subthalamic nucleus and normally exhibits sparse NT-IR displayed intense NT-IR following the chemical lesion.