Interactions between norepinephrine antagonists and potentiators (chlorpromazine, chlorpromazine sulfoxide and imipramine) and sympathetic amines (amphetamine and methoxamine) on the flexor reflex of the chronic spinal dog

The interactions of chlorpromazine (5 mg/kg), chlorpromazine sulfoxide (5 mg/kg) or imipramine (0·5 mg/kg), agents which have both adrenergic-blocking and adrenergic-potentiating properties, with amphetamine (2 mg/kg) or methoxamine (0·88 mg/kg), indirectly and directly acting sympathetic amines, were studied on the flexor reflex of the chronic spinal dog. Both methoxamine andd-amphetaminefacilitate the flexor reflex. Chlorpromazine completely antagonized the facilitatory effects of both methoxamine andd-amphetamine. Chlorpromazine sulfoxide and imipramine partially antagonized the facilitatory action of methoxamine; however, the antagonism was surmounted. Neither chlorpromazine sulfoxide nor imipramine antagonized the facilitatory effect of amphetamine; in fact, it was somewhat enhanced by chlorpromazine sulfoxide. It has been concluded that the central adrenergic-blocking property of chlorpromazine predominates, whereas, the adrenergic-blocking and adrenergic-potentiating effects of chlorpromazine sulfoxide and imipramine counterbalance each other.