BRAIN STRUCTURES INVOLVED IN THE BEHAVIORAL STIMULANT EFFECT OF CENTRAL SEROTONIN RELEASE

Drugs such as p-chloroamphetamine or a combination of tranylcypromine and tryptophan release serotonin in the central nervous system and pro duce a behavioral serotonin syndrome. However, in the presence of meth ysergide or following destruction of descending spinal serotonergic pr ojections by 5,7-dihydroxytryptamine, central serotonin release produc es hyperlocomotion. This supports the hypothesis that release of serot onin in the brain promotes locomotion but that the expression of this effect can be blocked by concomitant intraspinal effects of serotonin release. Hyperlocomotion induced by serotonin release is attenuated or blocked by: (a) pretreatment with p-chlorophenylalanine; (b) acute su rgical lesions of the basal diencephalon; (c) chronic lesions of the v entromedial midbrain tegmentum by local injection of 5,7-dihydroxytryp tamine; and (d) acute surgical decortication. Medial decortication ten ds to be more effective then lateral decortication. Hyperlocomotion pr oduced by methamphetamine is also attenuated or blocked by acute basal diencephalic lesions or decortication. It is suggested that ascending serotonergic and dopaminergic projections collaborate in the generati on of spontaneous voluntary motor activity. (C) 1997 Elsevier Science B.V.