[Vesico-anal correlations during miction in human beings]

1. The electrical activity of external anal sphincter (EAS) and internal anal sphincter (IAS), and the endo-anal pressure were recorded during the miction on 10 male adults with no signs of anorectal nor urologic affection. 2. During the premictionary period, the sympathetic hypertonicity was due to a large vesical proprioceptive activity; that initiated a higher frequency and amplitude of the IAS slow potential oscillations, and masked the inhibitory parasympathetic effect usually triggered by rectal distension. 3. During the vesical systolic phase the vesico-anal reflex induced by a parasympathetic activation and by: (a) a total absence of the EAS electrical activity during the duration of the miction period; (b) a two stage development of the IAS electrical activity: a tonic first stage of short duration and constant activity, followed by a second larger stage of variable form in accordance with the type of pattern (tonic, intermediary of which followed a similar developmental stage to that of the IAS. 4. This vesico-anal reflex makes it possible to assume that IAS activity plays a specific and important functional role in the maintenance of anal continence.