Clinical observations with pizotifene (Sandomigran) in the treatment of nonmigrainous depressed women

The effect of some new antidepressants on apomorphine-induced hypothermia in mice

Imipramine-like tricyclic antidepressants antagonize hypothermia induced by apomorphine in mice (Lapin & Samsonova 1968; Schelkunov 1968, 1977; Fuxe & Sjöqvist 1972; Maj et al 1974; Puech et al 1978); this phenomenon has been used by some authors as a test for the antidepressant activity. Therefore, we have examined the effect of some new antidepressants in this test, especially as some of them differ in their mechanism of action from imipramine-like drugs. The drugs used were: nomifensine, an inhibitor of the dopamine and noradrenaline (NA) uptake (Hunt et al 1974; Schacht & Heptner 1974), two specific inhibitors of 5-hydroxytryptamine (5-HT) uptake, femoxetine (FG 4963) (Buus Lassen et al 1975) and poroxetine (FG 7051) (Petersen et al 1977), two other antidepressants whose main characteristic was the blockade of central 5-HT receptors, i.e. mianserin (van Riezen 1972) and trazodone (Baran et al 1979). We also included pizotifen, a drug used in migraine prophylaxis (see Speight & Avery 1972) but exerting an antidepressant effect (Standal 1977; Banki 1978) and a potent central anti 5-HT activity (Dixon et al 1977; Przegalinski et al 1979). For comparison, the effect of four tricyclic antidepressants (imipramine, desipramine, amitriptyline and chlorimipramine) was also studied.

The central action of pizotifen

The central action of the potential antidepressant drug pizotifen (Sandomigran) was studied in mice, rats and rabbits. Pizotifen in doses up to 10 mg/kg i.p. was ineffective in classic tests for antidepressant activity. It neither antagonized the effects of reserpine in rats (hypothermia, ptosis) nor potentiated the effects of amphetamine (in mice and rats), nialamide or L-dopa (in mice) on locomotor activity. However, its antidepressant activitiy was found in the 'despair test' in rats. On the other hand, pizotifen inhibited the head twitch reaction induced by L-5-hydroxytryptophan in mice (ED50 = 0.009 mg/kg, i.p.) and by 5-methoxytryptamine (+ tranylcypromine) in rats (ED50 = 0.45 mg/kg, i.p.). It also antagonized tryptamine-induced clonic convulsions of fore-paws in rats (ED50 = 0.35 mg/kg, i.p.), and in doses of 5--10 mg/kg s.c. inhibited hyperthermia produced by LSD in rabbits. Finally, pizotifen (0.1--0.3 mg/kg, i.v.) inhibited or abolished LSD- or quipazine-induced stimulation of the hind limb flexor reflex of spinal rats; the above effect was not due to noradrenolytic action of the drug. These results suggest that pizotifen strongly blocks the central postsynaptic serotonin receptors.