Neurogenic adaptation contributes to the afferent response to mechanical stimulation

This study aimed to characterize the effect of mechanical stimuli on mesenteric afferent nerve signaling in the isolated rat jejunum in vitro. This was done in order to determine the effect of mechanical stresses and strains relative to non-mechanical parameters (neurogenic adaptation). Mechanical stimulations were applied to a segment of jejunum from fifteen rats using ramp distension with water at three rates of distension, a relaxation test (volume maintained constant from initial pressure of 20 or 40 mmHg) and a creep test (pressure maintained constant). Circumferential stress and strain and the spike rate increase ratio were calculated for evaluation of afferent nerve activity during the mechanical stimulations. Ramp distension evoked two distinct phases of afferent nerve signaling as a function of circumferential stress or strain. Changing the volume distension rate did not change the stress-strain relationship but faster distension rate increased the afferent firing rate (P