ADRENERGIC-NERVE FUNCTION AND CONTRACTILE ACTIVITY OF THE CAUDAL ARTERY OF THE STREPTOZOTOCIN DIABETIC RAT

The adrenergic nerve function and contractile responses of the densely innervated caudal artery of the 8-week streptozotocin (SZ) (65 mg/kg i.p.) diabetic rat were investigated. Segments of this artery were removed from diabetic and control rats, placed in Krebs-filled tissue baths (37.degree. C) and isometric tension recorded. Contractile responses to sympathetic nerve activation by electrical stimulation and to cumulative of norepinephrine (NE) and tyramine were recorded. In order to determine NE content, the NE was extracted from the caudal artery, isolated by adsorption chromatography, and quantified by HPLC with electrochemical detection. NE accumulation and release were also studied by quantifying the amount of tritiated NE ([3H]NE) and its metabolites in extracts of the tissue or incubation medium. The responses of the caudal artery of SZ diabetic rats to electrical stimulation (4-16 Hz) and to tyramine (1 .times. 10-5-1 .times. 10-4 M) were significantly less than those of arteries from control rats and the NE content reduced by 41%, while sensitivity to NE was unchanged. Diabetic arteries also accumulated and released more [3H]NE than did arteries from control rats. These results establish that neurovascular function of the isolated caudal artery of the 8-week SZ diabetic rat is abnormal and suggest that problems in the ability of adrenergic nerves to store and release NE may contribute to this dysfunction. Such changes may play a role in the cardiovascular disturbances associated with diabetic autonomic neuropathy.