Influences of androgen for detrusor function

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Male Sprague-Dawley rats, 16 weeks old, were used for this study. These rats are divided into two groups both castration and control. 4 weeks after castration, using isolated detrusor strips which were taken from these both bladders and mounted in an organ bath, in vitro contraction studies were performed to evaluate the contractile responses to agonist, the responses to electrical field stimulation(EFS) and the force-velocity relation to determine power of detrusor muscle. The dose-response curves for carbachol and α, β -methylene ATP did not differ from both detrusor strips. Thus, function of muscarinc receptor and purinoceptor were not changed after castration. EFS (15 voltage, 0.5msec duration) produced frequency -dependent contraction. At lower frequency(below 10 Hz), there seems to be slightly weak responses in castration group. However, at high frequency, the contractile responses were not altered. These results may suggest that castration influences function of nerve and/or secretion of neurotransmitters such as purinergic neuron. Power consists of force(F) and speed contraction(V) of muscle. Thus, we carried out an isotonic contraction study to measure velocity of detrusor muscle contraction. When EFS (50Hz) is applied, detrusor strip shortens against various loads. This velocity of shortening is calculated from a gradient of this shortening curve. A force-velocity curve, of castration group is situated under the curve of control group. Average power per unit tissue weight were 6.57 × 10^<-3>watt/g on control group and 3.18 × 10^<-3>watt/g on castration group. This study suggests that ancirogen influences power of detrusor muscle, directly. Bladder muscle could be a possible target of androgen.