The effect of STZ-induced diabetes of 8-weeks duration was examined on nitric oxide-mediated neurotransmission in the rat anococcygeus muscle. In the presence of noradrenergic blockade and raised tissue tone, relaxant responses to nerve stimulation (0.5-5 Hz, for 10 s), sodium nitroprusside (5 and 10 nmol/1) and nitric oxide (1 and 3 gmol/l) were significantly reduced in anococcygeus muscles from diabetic rats compared to responses from control rats (p < 0.05). In contrast, relaxations to papaverine (3 and 10 gmol/1) were not reduced in tissues from diabetic rats. The nitric oxide synthesis inhibitor NOLA (100 gmol/1) abolished relaxant responses to nerve stimulation but had no effect on responses to any of the relaxant agents used. Exposure to NOLA at 10gmol/1 reduced stimulation-induced relaxations; this reduction was significantly greater in tissues from the diabetic group than from the control group (p < 0.05), probably as a consequence of the smaller relaxant responses in muscles from diabetic rats. Contractile responses to nerve stimulation (1-10 Hz, for 10 s), but not noradrenaline (0.03-30 gmol/1), were significantly greater in anococcygeus muscles from diabetic rats than from control rats (p < 0.05). NOLA (100gmol/1) significantly enhanced stimulation-induced contractions (p < 0.05), however the enhancement was significantly less in tissues from diabetic rats (p<0.05). The results suggest that STZ-induced diabetes impairs smooth muscle reactivity to nitric oxide in the rat anococcygeus muscle. [Diabetologia (1994) 37: 232-237] Key words Anococcygeus muscle (rat), diabetes, nitrergic nerves, nitric oxide, NOLA, NANC transmission, nonvascular smooth muscle, sodium nitroprusside, streptozotocin.
Neuropathy of the autonomic nervous system is a complication of diabetes mellitus which may contribute to alterations in cardiovascular, gastrointestinal and genitourinary function [1,2]. These alterations may be manifested through clinical problems including postural hypotension, diabetic diarrhoea, diabetic cystopathy and impotence. The STZ-treated rat, an estab-