The initiation of non-micturating contractions in the feline bladder

The extrinsic nervous system of the bladder may not be involved in the initiation of non-micturating contractions in the cat, because neither the sympathetic or parasympathetic motor drives appear to change their level of activity before the first contraction. This stability of the motor drives may only reflect the absence of afferent drive from the relatively empty bladder. This assumption was examined by recording from the pelvic nerve during bladder filling at a natural rate in pentobarbitone anaesthetized cats. Afferent multifibre nerve activity was always increasing before the onset of non-micturating contractions. Six out of nine nerve fibres innervating localized bladder wall mechanoreceptors were discharging before the onset of non-mictating contractions, whereas all had been silent with the bladder empty. Because mechanoreceptor activity preceded the onset of non-micturating contractions, reflex changes in autonomic motor activity, which have not yet been observed, may have a role in initiating non-micturating contractions.