D-2 DOPAMINE-RECEPTOR PROTEIN LOCATION - GOLGI IMPREGNATION-GOLD TONED AND ULTRASTRUCTURAL ANALYSIS OF THE RAT NEOSTRIATUM

The neostriatal distribution of D-2 dopamine receptor protein has been assessed using subtype-selective polyclonal antibodies generated agai nst three unique polypeptide sequences of the receptor. The experiment al tissues were processed by peroxidase based immunohistochemical proc edures for routine light microscopy, Golgi impregnation-gold toned mor phological characterization, and correlative light/electron microscopy . The results demonstrated a regional gradient of D-2-like dopamine re ceptor expression in the neostriatum, where lateral portions in the nu cleus exhibited more reactive cell bodies than medial portions. D-2-li ke expression was detected in the three populations of neostriatal neu rons, i.e., the medium-sized spiny projection neurons, and the medium- and large-sized aspiny interneuron types. Morphometric measurements o f labeled neurons verified that medium and large diameter neurons expr essed the D-2-like receptor subtype. D-2-like immunoreactivity was dis tributed throughout the cytoplasm in dendritic processes, and in presy naptic terminal boutons. Immunoreactivity for the receptor protein was also detected in small, thinly myelinated axons, suggesting the possi bilities of anterograde transport of the receptor from cell bodies in the substantia nigra to their neostriatal terminal fields, as well as from local axon collaterals of neostriatal projections neurons. These findings provide evidence of widespread distribution of the D-2-like r eceptor protein in neostriatal neurons, and showed that the presynapti c D-2 receptors contain analogous epitopes to the postsynaptic recepto r subtype. (C) 1993 Wiley-Liss, Inc.