Small intestinal transplantation in the rat: effect on physiological properties of smooth muscle and nerves.

The effect of transplantation on the physiological and pharmacologic properties of small intestine was evaluated in a syngeneic rat model. We examined the intrinsic contractile properties of the smooth muscle, the neural control of intestinal motility, and the sensitivity of the muscle and nerve endings to biologically active compounds in vitro, comparing transplanted tissue to controls. Both graft and control tissue contracted in a dose-dependent manner to cholinergic agonists, 5-hydroxytryptamine, and substance P and relaxed in response to noradrenaline. Contractile properties of smooth muscle and sensitivity to drugs were not altered by transplantation. Excitatory innervation was also similar in all specimens, but the inhibitory response was altered by transplantation. In the control intestine inhibition became maximal above 30 Hz, while in the graft maximal inhibition was obtained at 5 Hz. These findings imply an absence of extrinsic adrenergic inhibitory innervation in the graft. Intrinsic nonadrenergic inhibitory nerves and the excitatory innervation were intact after transplantation.