Behavioral analysis of the postnatal development of micturition in kittens

Micturition in neonatal mammals of various species can be induced by a somatovesical reflex that is triggered by the mother licking the perineal region of the neonate. The present study was conducted to ascertain whether neonatal kittens can also urinate via a vesicovesical reflex that is elicited by bladder distension. Initial experiments consisted of isolating kittens from their mothers and observing urine release. Kittens less than 3 weeks of age did not urinate despite the presence of large volumes of urine in their bladders. Kittens older than 3 weeks of age did urinate, completely emptying their bladders. The volumes of urine that induced micturition in the older kittens were generally less than those that were ineffective in inducing micturition at younger ages. Cystometrograms in unanesthetized kittens less than 3 weeks of age revealed that distension of the bladder by saline infusion did not evoke bladder contractions. However, saline infusion in older kittens did produce bladder contractions that were accompanied by squatting and the release of urine from around the bladder cannula. Surprisingly, bladder contractions, which were typically abolished by spinal transection, were observed in kittens less than 3 weeks of age when the kittens were anesthetized with either ketamine or chloralose. This latter finding indicates that the vesicovesical reflex is present in neonatal kittens, but it is being suppressed by anesthetic-sensitive mechanisms. Thus, micturition in neonatal kittens is normally mediated entirely by the somatovesical reflex.