EFFECT OF EXTRINSIC DENERVATION IN A CANINE MODEL OF JEJUNOILEAL AUTOTRANSPLANTATION ON MECHANICAL AND ELECTRICAL-ACTIVITY OF JEJUNAL CIRCULAR SMOOTH-MUSCLE

Little is known about the acute and chronic effects of the intestinal transplantation on smooth muscle contractile physiology. Our aim was t o determine the effects of the denervation necessitated by jejunoileal autotransplantation on membrane potential and contractile activity. S ix dogs underwent a model of jejunoileal autotransplantation that spec ifically avoids ischemia/reperfusion injury (by maintaining blood flow to the gut during the ''transplantation'' procedure). Strips of jejun al circular muscle were studied sequentially before and 2 and 8 weeks after denervation by recording mechanical and intracellular electrical activities in vitro. The amplitude of spontaneous contractions ((X) o ver bar +/- SD) was increased (P < 0.05) at 2 compared to 0 weeks (126 +/- 19 vs 77 +/- 32 g/g; P < 0.05) but markedly decreased at 8 weeks (7 +/- 2 g/g). Contraction frequency, resting membrane potential, and amplitude of slow waves were unchanged across these time points. Betha nechol (10(-7)-10(-4) M) and substance P (10(-8)-10(-6) M) dose-depend ently increased contractile activity at all time points, but the absol ute change in amplitude was decreased at 8 weeks. The amplitude of inh ibitory junction potentials (IJPs) and duration of inhibition of contr actile activity in the presence of cholinergic and adrenergic blockade increased at 2 and 8 weeks; off-contraction amplitude was decreased a t 8 weeks (P < 0.05). These effects may occur via changes in neurotran smitter release, changes in regulation of membrane receptors, or alter ation of characteristics of the membrane threshold potential.