Micturition reflexes in decerebrate and spinalized neonatal rats

Micturition in neonatal rats is mediated by a spinal reflex pathway activated by the mother licking the perineum (the perineal-to-bladder reflex, P-Bld). Micturition in adult rats is mediated by a spinobulbospinal reflex pathway activated by bladder distension (the bladder-to-bladder reflex, Bld-Bld). This study examines the postnatal development of the Bld-Bld reflex in decerebrate or spinalized unanesthetized and urethan-anesthetized rat pups 2-26 days of age. Urethan anesthesia depressed both the Bld-Bld and P-Bld micturition reflexes. Bld-Bld micturition reflexes (peak intravesical pressures of 13 +/- 6 cmH2O and durations of 35 +/- 11 s) were noted in 54% of 2-day-old decerebrate pups and in all of the 6- and 9-day-old decerebrate pups but in none of the 2- or 9-day-old spinalized pups. We conclude that a weak supraspinal Bld-Bld reflex is present during the early postnatal period; however, the P-Bld reflex is the primary mediator of micturition in the neonatal rat.