Abstract
Effects of 4'-ethyl-2-methyl-3-piperidinopropiophenone hydrochloride (EMPP) on experimental rigidities in rats and spinal cord activities in cats were studied. EMPP in a dose range of 1.25 ?? 10 mg/kg i.v. reduced EMG spikes of the intercollicular decerebrate rigidity and anemic decerebrate rigidity in rats. In α-chloralose anesthetized cats, EMPP in a dose range of 2.5 ?? 10 mg/kg i.v. caused a dose-related inhibition of the flexor reflex without any effect on the patellar reflex. In spinal cats, 2.5 ?? 10 mg/kg of EMPP caused a dose-related inhibition of the flexor reflex but the potency was less than that in anesthetized cats. Oral administration of EMPP 100 ?? 200 mg/kg produced a selective inhibition of the flexor reflex and the effect was twice as potent as tolperisone and chlormezanone. On the other hand, EMPP at 2.5 ?? 10 mg/kg i.v. which had little effect on the patellar reflex inhibited both monosynaptic and polysynaptic reflex potentials recorded from the ventral root to the same extent and also depressed dorsal root reflex potential recorded from the dorsal root in spinal cats. EMPP reduced the frequency of spontaneous γ-motoneurone discharges in spinal cats, but had no appreciable effect on GIa discharges from muscle spindle of the triceps surae muscle. These results indicate that EMPP reduces α- and γ-efferent activities and that EMPP exerts a marked inhibitory effect on spinal cord activities acting on the spinal cord and supraspinal structures.
