Inhibitory Effect of Difenamizole on Morphine-Induced Straub Tail Reaction with Special Reference to Monoaminergic Agents

In order to elucidate the mechanism of difenamizole (DFZ)-induced inhibition of Straub tail reaction (STR), the relationship between biogenic amines and DFZ-induced inhibition of STR (DIS) was particularly investigated in this experiment. 10 mg/kg of apomorphine and 2 mg/kg of methamphetamine decreased the DIS (intraperitoneal and intracerebral injection of DFZ) significantly without producing marked STR. Intracerebral injection of 50 (μg/mouse of 5-hydroxytryptamine increased the DIS without affecting STR. On the other hand, the DIS was developed markedly, whether or not mice were pretreated with L-dopa, propranolol, disulfiram, l-5-HTP, tetrabenazine, nialamide, isocarboxazid and tranylcypromine. These results suggest that the DIS might at least be modulated by the variation in the activity of either catecholamine or tryptamine in the central nervous system of mice. In addition, the action mechanism of DFZ on STR was different from that on nociceptive reaction reported previously.