The effect of lysergic and diethylamide (LSD) and 2-bromolysergic acid diethylamide (BOL) on the striatal DOPA accumulation: influence of central 5-hydroxytryptaminergic pathways.

Selective chronic lesions of the dorsal raphe nucleus or combined lesions of the dorsal and median raphe nuclei did not significantly change the in vivo tyrosine hydroxylation in the striatum as measured by the DOPA accumulation after decarboxylase inhibition. Neither did acute combined lesions of the raphe nuclei, nor did electrical stimulation of the dorsal raphe nucleus have any significant effect. p-Chloroamphetamine (PCA, 20 mg/kg, i.p.) and p-chlorophenylalanine (PCPA, 400 mg/kg, i.p.), known inhibitors of the 5-hydroxytryptamine (5-HT) synthesis, significantly decreased the DOPA accumulation. The increase in DOPA accumulation observed after LSD (0.5 mg/kg, i.p.) or BOL (0.5 mg/kg, i.p.) was seemingly unaffected by pretreatment with PCA or PCPA and also after lesion of the dorsal raphe nucleus. The results suggest that the effect of LSD or BOL on the DOPA accumulation in the striatum is not mediated via a 5-hydroxytryptaminergic control mechanism originating in the dorsal raphe nucleus. A control mediated via the median raphe nucleus cannot be excluded, since LSD did not increase the DOPA accumulation after combined chronic raphe lesions. Such a control would also be in agreement with our previous results suggesting that hte DOPA generation after LSD is controlled by 5-HT receptors.