Effect of serotonin uptake blocking agents on the flexor reflex of hind limb of the spinal rat

Imipramine, clomipramine, FG 4963 and quipazine potentiated the flexor reflex of hind limb of the spinal rat, imipramine and clomipramine being relatively weak, and quipazine the most potent in this respect. The potentiation is prevented by serotonin receptor blocking agents, cyproheptadine and danitracen. Imipramine and clomipramine prevented the potentiation of flexor reflex by fenfluramine; this indicates a presynaptic mechanism of action of the latter compound. The stimulatory action of LSD is only partially inhibited by imipramine. The action of quipazine seems to be mainly postsynaptic, as it is not prevented by severe depletion of serotonin stores by reserpine and an inhibitor of serotonin synthesis, H 22/54.