Morphometrical evidence for a complex organization of tyrosine hydroxylase-, enkephalin- and DARPP-32-like immunoreactive patches and their codistribution at three rostrocaudal levels in the rat neostriatum.

Tyrosine hydroxylase-like, dopamine- and cyclic AMP-regulated phosphoprotein (Mr = 32,000)-like and enkephalin-like immunoreactive profiles and their codistribution have been evaluated at three rostrocaudal levels of the rat neostriatum by means of a computer-assisted morphometrical method, which allows an objective definition of high density/intensity patches using specific antibodies in combination with the peroxidase-antiperoxidase technique. Our results show that both tyrosine hydroxylase-like, dopamine- and cyclic AMP-regulated phosphoprotein-like and enkephalin-like profiles are organized in patches in the rat neostriatum. In the marginal zone, the tyrosine hydroxylase-like immunoreactive and dopamine- and cyclic AMP-regulated phosphoprotein-like immunoreactive patches both occupied a large part of the total area. Moreover, in this zone, these putative markers for pre- and postsynaptic elements of dopaminergic synapses also showed a complete spatial overlap. In contrast, the enkephalin-like immunoreactive patches in the marginal zone occupied a smaller area, and showed only an incomplete, albeit significant overlap with the tyrosine hydroxylase-like immunoreactive/dopamine- and cyclic AMP-regulated phosphoprotein-like immunoreactive system. In the central zone, tyrosine hydroxylase-like immunoreactive, dopamine- and cyclic AMP-regulated phosphoprotein-like immunoreactive and enkephalin-like immunoreactive patches occupied a much smaller part of the total area than did those in the marginal zone. Within the central zone, enkephalin-like immunoreactive patches occupied a significantly larger area than did the tyrosine hydroxylase-like immunoreactive and dopamine- and cyclic AMP-regulated phosphoprotein-like immunoreactive patches. No consistent pattern of overlap between the three different staining patterns could be seen in the central zone, probably due to the small, inconsistent size of the patches. Trend analysis showed a consistent trend of more tyrosine hydroxylase-like immunoreactive and dopamine- and cyclic AMP-regulated phosphoprotein-like immunoreactive patches in the dorsal than in the ventral striatum, and a trend of more enkephalin-like immunoreactive patches in the rostral than in the caudal striatum. Our data thus demonstrate that, by using computer-assisted morphometrical techniques, it is possible to describe a non-homogenous but overlapping distribution of tyrosine hydroxylase-like immunoreactive and dopamine- and cyclic AMP-regulated phosphoprotein-like immunoreactive patches in the rat neostriatum.