Effect of streptozotocin diabetes on motor and inhibitory transmission in rat anococcygeus.

The effect of streptozotocin diabetes of 4-week duration on the adrenergic motor transmission and on the nonadrenergic, noncholinergic, inhibitory transmission in the rat anococcygeus was investigated by recording contractile and relaxant activity of isolated muscle preparations taken from diabetic and age-matched control animals. The neurogenic contractile responses to electrical field stimulation were significantly reduced in the preparations from diabetic rats. The inhibitory transmission remained unaffected in the diabetic rats. Concentration--response curves showed no change in sensitivity of the diabetic anococcygei to noradrenaline. The maximum tension generated was also similar in preparations from diabetic and nondiabetic animals. The contractile responses to electrical field stimulation were significantly greater in preparations from diabetic rats treated for 4 weeks with either sorbinil (20 mg.kg-1.day-1 orally) or myo-inositol (667 mg.kg-1.day-1 orally) when compared with the untreated diabetic controls; the sensitivity to noradrenaline was identical in all three groups. It is concluded that streptozotocin diabetes causes a significant reduction of adrenergic contractile responses of the anococcygeus to electrical field stimulation by a prejunctional mechanism, and the reduction can be prevented by treating the animals with the aldose reductase inhibitor sorbinil or with myo-inositol.