Temporal changes in mechanical properties of rat jejunal smooth muscle after myenteric plexus ablation

We determined length-stress properties and active tension development of rat jejunal longitudinal and circular muscle at various times after myenteric neuron ablation. Myenteric neurons were destroyed by serosal application of benzalkonium chloride. Active tension generation in response to both carbachol and barium was depressed in both muscle layers up to 7 days after treatment, at which times the responses were normal. At 15 days, circular muscle responses were still comparable to control, but longitudinal muscle responses were significantly increased. Length-stress parameters of circular muscle were minimally affected, while those of longitudinal muscle were significantly altered 15 and 30 days after treatment. These alterations include changes in resting stress and increased active stress generation at both times. Our results suggest that 1) normal myenteric innervation is necessary for normal contractile activity in rat jejunal smooth muscle and 2) changes in cellular or tissue morphology or alterations in intracellular calcium homeostasis, as seen in other tissue, may occur after myenteric plexus ablation.