The dependence of sustained bladder contractions provoked by filling or by subcutaneous bethanechol upon sacral afferent pathways

The dependence of the detrusor response to sc bethanechol chloride on afferent nerves was studied in 20 cats by selective dorsal rhizotomy L₇‐S₃ in different combinations. Combined S₁ and S₂ dorsal rhizotomy abolished both the micturition reflex and the sustained bladder contraction in response to sc bethanechol administration. However in six of 13 experiments selective S₂ dorsal rhizotomy abolished the bethanechol response while leaving the mictu rition reflex intact, albeit with a higher threshold volume. On the other hand, the bethane chol response was always lost if the micturition reflex was lost. We conclude that the sustained bladder response to sc bethanechol requires a complete reflex pathway involving sacral dorsal roots.