Immunocytochemical localization of dopamine in the prefrontal cortex of the rat at the light and electron microscopical level

Abstract

In the present study the dopaminergic innervation of the prefrontal cortex was studied by means of a recently developed anti-dopamine serum. This method can demonstrate endogenous dopamine in a specific way, and offers the opportunity to study the distribution of dopaminergic fibres in the cortex in detail in counterstained sections. Furthermore, dopaminergic nerve endings can be visualized at the electron microscopic level. Light microscopic observations demonstrated that the highest density of dopaminergic fibres in the frontal cortex is found in the prefrontal cortex and the infralimbic cortex. Within the prefrontal cortex, a good correlation is found between regional differences in distribution of dopaminergic fibres and the cytoarchitectonic parcellation of this part of the cortex. Outside the prefrontal cortex dopaminergic fibres were observed in adjacent frontal areas, the cortex surrounding the entire rhinal sulcus and the retrosplenial cortex. Electron microscopic observations demonstrated dopaminergic terminals through all cortical layers. The majority of dopaminergic terminals in the prefrontal cortex from synaptic contacts with dendritic processes. The synaptic profiles were usually symmetric and were characterized by the presence of many clear vesicles and an occasional dense-core vesicle.