Direct Evidence for Contribution of Muscarinic Receptors to the Facilitation of Primary Bladder Mechanosensitive C-fiber Afferents in the Rat

Hypothesis / aims of study It has been reported that bladder muscarinic receptor (mAChR) may have a physiological role in the bladder afferent functions, especially in the C-fibers (1). In addition, a previous study demonstrated that bladder mechanosensitive C-fibers can be classified as capsaicin-sensitive and capsaicin-insensitive, and imidafenacin (IMF), a mAChR antagonist, selectively inhibited the capsaicinsensitive subgroup of these C-fibers (2). Moreover in clinical observation, a considerable part of the patients with overactive bladder (OAB) do not respond to the treatment of antimuscarinic agents (3). Therefore, we hypothesized that bladder mechanosensitive C-fiber afferent nerves have various sensitivities to the mAChR stimulation. In this study, we investigated the relationship between the afferent activities and oxotremorine-M (Oxo-M, a mACR agonist)-sensitivity in the normal urethane-anesthetized rat by using the single-unit afferent activities (SAAs) measurement.