EFFECTS OF A NEW CENTRALLY ACTING MUSCLE-RELAXANT, NK433 (LANPERISONEHYDROCHLORIDE) ON SPINAL REFLEXES

3-(1-pyrrolidinyl)-4'-trifluoromethylpropiophenone monohydrochloride, lanperisone hydrochloride (NK433) administered intravenously or orally depressed the mono-and polysynaptic reflex potential, dorsal root ref lex potential, flexor reflex mediated by group II afferent fibers, pat ellar and flexor reflexes. These effects were reduced by spinal transe ction. NK433 inhibited the facilitation of the flexor reflex mediated by group II afferent fibers that was induced by intrathecal administra tion of noradrenaline-HCl. rrolidinyl)-1-(4-trifluoromethylphenyl)-1-p ropano: (LPS-9)-HCl, a metabolite of NK433, also inhibited the spinal reflexes. Given orally, NK433 had effects more than three times strong er and tending to be longer-lasting than those of eperisone-HCl. These results suggest that NK433 exerts a non-selective inhibition on spina l reflexes and that inhibition of the descending noradrenergic tonic f acilitation within the spinal cord is involved in the mechanism of spi nal reflex depression by NK433. LPS-9 could contribute to the potent a ctivity of NK433 after oral administration. (C) 1997 Elsevier Science B.V.