A study of the sites of interaction between dopamine and 5-hydroxytryptamine for the production of fluphenazine-induced catalepsy.

The effect of reducing 5-hydroxytryptamine (5-HT) concentration within various areas of the central dopamine (DA) system on catalepsy has been investigated. The neurotoxin 5,7-dihydroxytryptamine was used to selectively deplete 5-HT in the striatum, nucleus accumbens septi, tuberculum olfactorium or substantia nigra. Localised depletion of 5-HT within the nucleus accumbens septi and substantia nigra reduced the cataleptic effects of the neuroleptic agent fluphenazine, while lesions of the striatum or tuberculum olfactorium were without effect. Each injection of neurotoxin resulted in a 38--47% depletion of 5-HT in the target site: DA levels were not significantly altered. The results suggest that varied dopamine/5-hydroxytryptamine interactions within the nucleus accumbens may contribute to the action of the neuroleptic. The reduction of fluphenazine-induced catalepsy produced by 5-HT depletion within the substantia nigra supports the concept of a controlling influence of 5-HT on nigro-striatal DA function.