Effect of diazepam on cerebral 5-hydroxytryptamine synthesis.

In the brains of normal and reserpinized rats both diazepam and amino-oxyacetic acid (AOAA) decreased the 5-hydroxytryptophan (5HTP) accumulation induced by the decarboxylase inhibitor 3-hydroxybenzylhydrazine (NSD 1015). In reserpinized animals, the action of diazepam was antagonized by picrotoxin and bicuculline in doses which did not themselves influence the NSD 1015-induced rise in 5HTP. In conclusion, diazepam probably depresses 5HT synthesis via GABAergic mechanisms and this effect is not dependent on a functionally intact monoaminergic synaptic transmission.