The effect of autonomic drugs and prostaglandinF2 alpha on the rectoanal inhibitory reflex

Anorectal manometry was performed on mongrel dogs given various drugs in attempts to determine the effect of the drugs on rectoanal inhibitory reflex. Anal canal pressure was significantly increased by the administration of neostigmine and noradrenaline and significantly lowered by isoproterenol. The amplitude of the rectoanal inhibitory reflex was increased by the administration of neostigmine and prostaglandinF2 alpha (PGF2 alpha), decreased by atropine but was little affected by either noradrenaline or isoproterenol. These results suggested that cholinergic neurons have an excitatory effect both on the anal canal pressure and the rectoanal inhibitory reflex, while adrenergic alpha and beta receptors have little effect on the rectoanal inhibitory reflex. PGF2 alpha was though to increase the motor activity of the anal sphincter and facilitate the rectoanal inhibitory reflex. Neostigmine and PGF2 alpha may aid in clarifying rectoanal inhibitory reflexes in neonates or postoperative children with rectoanal diseases.