Effects of acute administration of cyclazocine on the metabolism of biogenic amines in different regions of rat brain.

The effects of cyclazocine on the metabolism of dopamine (DA), noradrenaline (NA) and 5-hydroxytryptamine (5-HT) in regions of rat brain were studied by measuring changes in the levels of the monoamines and their major metabolites. Doses ranging from 4-32 mg/kg were tested. Rats were sacrificed 1 or 2 h after administration of the drug, according to the experiment. Administration of cyclazocine significantly decreased DA concentration and increased the levels of DOPAC and HVA in striatum. Cyclazocine decreased the levels of NA, and markedly increased the levels of MHPG-SP4 and 5-HIAA in cortex, hypothalamus, midbrain and pons-medulla, while little change in 5-HT concentration, except a decrease after the highest dose, was observed. These changes in the metabolism of the monoamines differed in their amplitude and temporal nature. The possible roles of dopaminergic, noradrenergic and serotoninergic neurons in different brain regions are discussed in relation to modifications of locomotor activity and the induction of bizarre behavior resulting from cyclazocine administration in rats. These investigations may add to the understanding of the mechanism of psychotomimetic effects produced in man by this drug.