LOCAL MUSCIMOL DISINHIBITS MESOLIMBIC DOPAMINERGIC ACTIVITY AS EXAMINED BY BRAIN MICRODIALYSIS AND FOS IMMUNOHISTOCHEMISTRY

Infusion of muscimol (5 x 10(-5) M, 60 min) into the nucleus accumbens (NAC) through a dialysis membrane caused a significant increase in ex tracellular dopamine (DA) and its metabolite, 3,4-dihydroxyphenylaceti c acid (DOPAC). Fos-Like immunoreactivity induced by intra-NAC infusio n of muscimol was seen ipsilaterally in many accumbofugal target areas , but no Fos-positive neurons were seen in the vicinity of the dialysi s membrane in the NAC. Sequential staining of Fos and tyrosine hydroxy lase (TH) immunoreactivities revealed that a portion of A10 dopaminerg ic neurons were double-labelled. These results suggest that muscimol i n the NAC disinhibits mesolimbic DA neuronal activity possibly through activity of the accumbofugal GABA neuron system. (C) 1997 Elsevier Sc ience B.V.