CALCIUM-CHANNEL AGONIST ANTAGONIST EFFECTS ON CHOLINERGIC STIMULATION OF THE DIABETIC RAT BLADDER

The in vitro effects of a calcium channel agonist (BAY K8644) and antagonist (nifedipine) on the cholinergic responses of the streptozotocin-induced diabetic rat bladder were investigated. The bladder body and bladder base were studied separately. There were significant differences in contractile responses to acetylcholine stimulation in the diabetic bladder body compared to the control body. Similarly, the diabetic bladder base demonstrated significantly increased contractile responses compared to the control base. Contractile responses in the diabetic bladder body and base were significantly increased from the control in the absence of extracellular calcium. Differences were found in the effects on maximum responses between diabetic and control tissues treated with nifedipine and BAY K8644. BAY K8644 did not completely reverse the effect of nifedipine on the contractile responses. Rates of contractile response were significantly different between controls and diabetics and between body and base. Alterations in calcium channel activity in diabetic bladder smooth muscle may be responsible at least in part for the nonspecific pharmacologic responses found in smooth muscle strips.