Bladder function in rats with short- and long-term diabetes; effects of age and muscarinic blockade

The development of alterations in urinary bladder function was studied in rats during six months of streptozotocin-induced diabetes. The results were compared with those obtained in age-matched controls. The bladders from the control rats developed with increasing age an increased micturition volume, a decreased micturition interval, and increased bladder compliance and capacity despite an unaltered bladder weight and unaltered passive and active length-tension relations. The effects of muscarinic blockade were somewhat more pronounced in the older control rats. Following streptozotocin 24 hour diuresis increased rapidly to stabilize within two weeks at a level 15 times higher than the original. This was accomplished initially by an increase in the micturition frequency and then gradually by an increased micturition volume. After six weeks bladder weight had increased more than twofold and did not increase further with time. Despite this both micturition volume and bladder capacity increased from six weeks to six months of diabetes. The diabetic bladders had at low frequencies of stimulation a higher resistance to scopolamine than their age-matched controls. At higher frequencies the resistance to muscarinic blockade showed a similar decrease with age as for the controls. The more pronounced decrease in micturition pressure following atropine treatment in six weeks diabetic rats thus suggests an increased excitation frequency during micturition. No supersensitivity to carbachol was found even after six months of diabetes.