LOSS OF DOPAMINE TERMINALS IN THE MEDIAL PREFRONTAL CORTEX INCREASED THE RATIO OF DOPAC TO DA IN TISSUE OF THE NUCLEUS-ACCUMBENS SHELL - ROLE OF STRESS

We examined whether dopamine depletion in the medial prefrontal cortex of the rat differentially affects basal and evoked dopamine and 3,4-d ihydroxyphenylacetic acid (DOPAC) content in the subareas of the neost riatum and nucleus accumbens. Loss of approximate to 80% of tissue dop amine content in the medial prefrontal cortex did not significantly al ter basal tissue concentrations of dopamine or DOPAC or the DOPAC:dopa mine ratio in either the nucleus accumbens core or shell or the medial or lateral neostriatum. However, tail pressure stress significantly i ncreased the DOPAC:dopamine ratio in the nucleus accumbens shell of le sioned rats. Because dorsal and ventral areas of the medial prefrontal cortex preferentially innervate the core and shell, respectively, we sought to determine whether the selective effect of lesions on dopamin e terminals in the shell of the nucleus accumbens are paralleled by gr eater dopamine loss in the ventral medial prefrontal cortex. 6-Hydroxy dopamine decreased tissue concentrations of dopamine in both the dorsa l (-74%) and ventral medial prefrontal cortex (-68%). In lesioned rats , few tyrosine hydroxylase-immunoreactive fibers remained in the dorsa l medial prefrontal cortex whereas a dense innervation remained in the ventralmost area. The present data suggest that the influence of meso cortical dopamine neurons on the dopamine projection to the nucleus ac cumbens shell is expressed only under conditions of stress. Furthermor e. lesion-induced alterations in dopamine neurons projecting to the nu cleus accumbens shell are not due to a more extensive loss of dopamine terminals in the ventral than in the dorsal medial prefrontal cortex. (C) 1997 Elsevier Science B.V.