Rectal intraganglionic laminar endings are transduction sites of extrinsic mechanoreceptors in the guinea pig rectum

Background & aims : Vagal afferent mechanoreceptors in the upper gut have recently been identified morphologically as intraganglionic laminar endings (IGLEs), but little is known about the structure of mechanoreceptive endings elsewhere in the gastrointestinal tract. We have morphologically characterized the nerve endings of specialized mechanoreceptors in the rectum. Methods : Extracellular recordings from guinea pig rectal and colonic nerves were made, in vitro, in combination with rapid anterograde transport of biotinamide, to reveal the morphology of recorded fibers. Controlled distentions were used to activate mechanoreceptive afferent units, and von Frey hairs were used to identify their transduction sites. Results : Rectal mechanoreceptors were present in high density, had low thresholds, and adapted slowly to maintained distention. Each afferent unit had multiple small (