Neural mechanisms and sedative effect of different fractions of Holarrhena floribunda (Apocynaceae) stem bark in mice

Holarrhena floribunda G. Don (Apocynaceae) stem bark is used locally in the treatment of mental illness in Nigeria.This work examined the neural mechanism and the sedative properties of the crude extract and its fractions. Acute toxicity studies were carried out on the crude extract and fractions by oral and intraperitoneal administration using Lorkes (1983) method. The effect of the crude extract of Holarrhena floribunda and the fractions; hexane, chloroform, ethylacetate, butanol and aqueous was examined on novelty-induced rearing and grooming behaviors and on pentobarbital-induced sleeping

time in mice, The results shows that the crude extract and the fractions were not toxic with the exception of butanol fraction. The crude extract and fractions reduced novelty-induced rearing and grooming behavior in mice. The inhibitory effect of the crude extract and the fractions were not reversed by atropine, cyproheptadine, yohimbine and naloxone; however the crude extract and the fractions blocked the facilitating effect of flumazenil. This suggests that the crude extract and the fractions appear to facilitate GABA-ergic transmission. The crude extract, aqueous, butanol and chloroform fractions prolonged pentobarbital-induced sleeping time in mice which were blocked by flumazenil a GABAA antagonist, indicating that the crude extracts, aqueous, butanol and chloroform fractions contain GABAA agonist. The result suggests that the stem bark of Holarrhena floribunda possess sedative effects which may be mediated through GABA-ergic neurotransmission.

Keywords: Holarrhena floribunda, Rearing, Grooming, Sedative, GABA

References: Lorke D (1983) Arch Toxicol 54: 275–287.