Histamine-Mediated Regulation of Electrical Activity during the Bladder–Urethra Interaction in Rats

Resumo

The effect of histamine on background spontaneous electrical activity of the interrelated bladder and urethra was studied in rats. The basic characteristics of pacemaker activity (action potential amplitude, average peak rise rate, peak rise time, peak half-width, rhythmogenicity frequency) were analyzed both in normal conditions and upon exposure to histamine (10^–4 mol/L). A comparison of the action potential parameters in the above organs demonstrated far lower values of the amplitude (by 34.19%; p ≤ 0.001), peak rise rate (by 30.39%; p ≤ 0.01) and peak rise time (by 18%; p ≤ 0.01) at a reduced rhythmogenicity frequency. Histamine evoked a considerable increase in the amplitude and its rise rate in the bladder (by 50.59 and 56.36%, respectively; p ≤ 0.001) and rhythmogenicity frequency (by 18%; p ≤ 0.01) at a constancy of the remaining two parameters. In the urethra, no obvious changes were detected in the action potential parameters. Morphohistochemical analysis also supported the involvement of histamine in the activation of rhythmogenicity only in the bladder. Thus, histamine is not implicated in the genesis of tonic contractions in the urethra, in contrast to its activating effect on the bladder.