Mechanosensory Transduction

Visceral afferent fibers convey a vast amount of sensory information to the brain stem and spinal cord. Two major mechanisms underlie signal transduction evoked by local distortion of nerve endings. The first is 'indirect,' or 'chemical,' transduction whereby another cell type (e.g., the enterochromaffin cell) is activated by the stimulus and then releases a transmitter such as 5-hydroxytryptamine onto the sensory axon, causing it to fire. The second is direct mechanosensitivity, which arises because of the presence of mechanically sensitive ion channels in the nerve terminal membrane. In addition to transduction mechanisms, substantial modulation of the excitability of peripheral sensory endings occurs during tissue injury and inflammation.