[Aim] High salt intake is a risk factor for urinary storage symptoms. In this study, we investigated the effects of high salt intake on detrusor muscle contraction in rats.

[Methods] Six-week-old male Dahl salt-resistant (DR, n = 5) and Dahl salt-sensitive (DS, n = 5) rats were fed a high salt diet (HS; 8% NaCl containing CE-2) for 1 week. The contractile responses of the detrusor muscle to cumulative administration of carbachol and electrical field stimulation (EFS) in the absence and presence of inhibitors (suramin; a purinergic receptor inhibitor, atropine; a muscarinic receptor inhibitor) were evaluated by measuring isometric tension.

[Results] Carbachol concentration versus response curves shifted to lower concentrations in the DS + HS group than those in the DR + HS group. Contractile responses to EFS were more enhanced in the DS + HS group than those in the DR + HS group. There was no difference in the purinergic components-induced contractile responses, whereas cholinergic components-induced contractile responses were more enhanced in the DS + HS than those in the DR + HS group.

[Conclusion] One week of high salt intake in DS rats enhanced detrusor muscle contraction via an increased sensitivity to cholinergic signals. Enhanced detrusor muscle contraction might lead to urinary storage symptoms.