REDUCTION IN CORTICAL 5-HT3 BINDING-SITES FOLLOWING A UNILATERAL 6-HYDROXYDOPAMINE LESION OF THE MEDIAL FOREBRAIN-BUNDLE IN RATS

Serotonergic mechanisms have been implicated in pathophysiology of Parkinson's disease, an illness where the dopamine deficiency represents the prime biochemical deficit. Present interest centres on the possible involvement of serotonergic receptors in modulating dopamine transmission. In this paper the binding of the selective 5-HT3 antagonist [H-3]GR 65630 was studied in rats with a unilateral 6-hydroxydopamine lesion of the medial forebrain bundle. The maximal density of specific [H-3]GR 65630 binding was reduced in homogenates of entorhinal (17.1%, P < 0.05) and prefrontal cortex (27.5%, P < 0.05) on the lesioned side of the rat brain compared to the control tissues. An increase in affinity for [H-3]GR 65630 binding was also found in homogenates of prefrontal cortex (33.8%, P < 0.05). No changes in the characteristics of [H-3]GR 65630 binding to homogenates from the amygdala and hippocampus were observed. These data suggest that altered dopamine function may affect serotonergic mechanisms in the cortex in Parkinson's disease.