Norepinephrine-induced contractile responses in isolated rat aortae from different duration of diabetes.

The present study examined contractile responses to norepinephrine in isolated aortae from 4-, 8-, and 12-week duration of streptozocin-induced diabetic rats. The pD2 value and the maximum contractile responses were significantly increased in 8-week and 12-week diabetic aortae, respectively, compared to the age-matched control aortae. Moreover, the bethanechol-induced relaxation of 12-week diabetic aortae preconstricted with norepinephrine was also significantly different from the age-matched control aortae. On the other hand, the KCl-, phenylephrine-induced contraction in 4-, 8-, and 12-week diabetic and age-matched control aortae were similar. Presumably the duration of diabetes altered the sensitivity and responsiveness of aortae to norepinephrine. The possibility of the enhanced norepinephrine response in diabetic aortae was discussed.