Central action of the antidepressant drug pirlindole

The central action of 2,3,3a,4,5,6-hexahydro-8-methyl-1H-pyrazino[3,2,1-j,k]carbazole hydrochloride (pirlindole, PIR) in mice and rats was studied. PIR inhibited the 3H-5-hydroxytryptamine (5-HT) uptake in the rat cerebral cortex, not affecting the uptake of 3H-noradrenaline. PIR counteracted the reserpine ptosis but did not alter the apomorphine hypothermia. It enhanced the L-dopa effect on the locomotor activity and the L-5-hydroxytryptophan (L-5-HTP)-induced head twitch reaction in mice. PIR also facilitated the effect of L-dopa and L-5-HTP on the hind limb flexor reflex of the spinal rat. The clonidine sedation (but not hypothermia) was attenuated by PIR. PIR given repeatedly for 18 days increased the binding of 3H-prazosin in the brain cortex (decreasing the KD value), but did not affect the binding of 3H-dihydroalprenolol. The obtained results indicate that PIR inhibits the 5-HT uptake, displays characteristics of a monoamineoxidase inhibitor and, when given repeatedly, increases the binding to alpha 1-adrenoceptors in the cerebral cortex.