[Pharmacologic studies of antimotion sickness actions of ginger]

The pharmacologic actions related to antimotion sickness effects of ginger (Zingiber officinale Roscoe.) were studied. There was no significant effect on parameters of rotatory movement-induced electronystagmogram of rabbit after intravenous (i.v.) infection of ginger juice. The low amplitude fast wave pattern of electrocorticogram of rabbit changed to high amplitude slow wave pattern after i.v. injection of ginger juice. Rabbit gastric contraction in situ was shortly suppressed after ginger juice i.v. administration. In the isolated rat fundus strip preparations, however, ginger juice reduced the spontaneous contractile frequency, and enhanced the spontaneous contractile amplitude, which was followed by inhibition. Ginger juice produced longitudinal contraction of the guinea-pig isolated ileum, which was followed by rapid tachyphylaxis. This contraction effect was not affected by hexamethonium and 5-HT, but could be inhibited by cold storage, hyoscine, morphine, diphenhydramine, promethazine and substance P desensitization. Naloxone could eliminate this inhibition produced by morphine. By using dose-response relationship plot, non-competitive antagonisms were observed between ginger juice and Ach and between ginger juice and histamine in isolated guinea-pig ileum. It is suggested that the pungent constituents of ginger release substance P from sensory fibres. The released substance P in turn either stimulates cholinergic and histaminic neurons to release Ach and histamine, respectively, or produces direct muscle contraction by activating M and H1 receptors correspondingly. It is proposed that after being excited by substance P, M and H1 receptors are inactive temporarily and unable to be excited by agonists, therefore, ginger juice exhibits anticholinergic and antihistaminic action. Ginger juice produces antimotion sickness action possibly by central and peripheral anticholinergic and antihistaminic effects.