Medial prefrontal cortex lesions inhibit reflex micturition in anethetized rats

The medial prefrontal cortex is thought to participate in the control of micturition and urinary continence, based on evidence from clinical reports, but its exact role is not fully understood. This study investigated whether ibotenic acid lesions of the medial prefrontal cortex would influence volume-evoked micturition in urethane-anesthetized rats. The incidence and amplitude of bladder contractions were recorded during continuous saline infusion (0.1 ml/min) immediately before and 1 week after ibotenic acid (0.5 microg) or vehicle (0.5 microl) was injected into the medial prefrontal cortex. Vehicle injection did not change the incidence or amplitude of bladder contractions compared to pre-injection values. Ibotenic acid lesions prolonged the time interval between bladder contractions significantly although it did not affect the amplitude of bladder contractions. Histological analysis revealed that ibotenic acid lesions were restricted primarily to the anterior cingulate and prelimbic cortices. Larger ibotenic acid lesions extending ventrally into the infralimbic cortex produced a variable response but did not change the overall incidence or amplitude of bladder contractions significantly. These data indicate that the medial prefrontal cortex influences the timing of bladder contractions but does not affect contraction amplitudes.