The residual nonadrenergic contractile response to nerve stimulation of the mouse prostate is mediated by acetylcholine but not ATP in a comparison with the mouse vas deferens

Abstract

Neuronal release of noradrenaline is primarily responsible for the contraction of prostatic smooth muscle in all species, and this forms the basis for the use of α(1)-adrenoceptor antagonists as pharmacotherapies for benign prostatic hyperplasia. Previous studies in mice have demonstrated that a residual nonadrenergic component to nerve stimulation remains after α(1)-adrenoceptor antagonism. In the guinea pig and rat prostate and the vas deferens of guinea pigs, rats, and mice, ATP is the mediator of this residual contraction. This study investigates the mediator of residual contraction in the mouse prostate. Whole prostates from wild-type, α(1A)-adrenoceptor, and P2X1-purinoceptor knockout mice were mounted in organ baths, and the isometric force that tissues developed in response to electrical field stimulation or exogenously applied agonists was recorded. Deletion of the P2X1 purinoceptor did not affect nerve-mediated contraction. Furthermore, the P2-purinoceptor antagonist suramin (30 μM) failed to attenuate nerve-mediated contractions in wild-type, α(1A)-adrenoceptor, or P2X1-purinoceptor knockout mice. Atropine (1 μM) attenuated contraction in prostates taken from wild-type mice. In the presence of prazosin (0.3 μM) or guanethidine (10 μM), or in prostates taken from α(1A)-adrenoceptor knockout mice, residual nerve-mediated contraction was abolished by atropine (1 μM), but not suramin (30 μM). Exogenously administered acetylcholine elicited reproducible concentration-dependent contractions of the mouse prostate that were atropine-sensitive (1 μM), but not prazosin-sensitive (0.3 μM). Acetylcholine, but not ATP, mediates the nonadrenergic component of contraction in the mouse prostate. This cholinergic component of prostatic contraction is mediated by activation of muscarinic receptors.

Fig. 1.

Mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in the prostate (A, C, and E) and vas deferens (B, D, and F) in the absence (open bars) and presence of (solid bars) prazosin (0.3 μM) (A and B), suramin (30 μM) (C and D), and atropine (1 μM) (E and F). Bars represent mean force ± S.E.M. (n = 6–7). P values determined by a two-way repeated-measures of ANOVA represent the probability of the drug treatment causing a significant change. *, P < 0.05; **, P < 0.01; ***, P < 0.001; solid bar versus control calculated by Bonferroni post-tests.

Fig. 2.

Comparison of mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in prostates (A and C) and vas deferens (B and D) taken from wild-type mice (open bars) and α_1A-adrenoceptor knockout mice (solid bars) (A and B) or P2X1-purinoceptor knockout mice (solid bars) (C and D). Bars represent mean force ± S.E.M. (n = 5–11). P values determined by a two-way repeated-measures of ANOVA represent the probability of the drug treatment causing a significant change. **, P < 0.01; ***, P < 0.001; solid bar versus control calculated by Bonferroni post-tests.

Fig. 3.

Mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in the prostate (A and C) and vas deferens (B and D) after the administration of prazosin (0.3 μM) (open bars) and prazosin (0.3 μM) plus atropine (1 μM) (solid bars) (A and B) and guanethidine (10 μM) (open bars) and guanethidine (10 μM) plus atropine (1 μM) (solid bars) (C and D). Bars represent mean force ± S.E.M. (n = 5–6). P values determined by a two-way repeated-measures of ANOVA represent the probability of the drug treatment causing a significant change. **, P < 0.01; ***, P < 0.001; solid bar versus control calculated by Bonferroni post-tests.

Fig. 4.

A and B, mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in prostates (A) and vas deferens (B) taken from α_1A-adrenoceptor knockout mice after the administration of no drug (open bars), prazosin (0.3 μM) (solid bars), and prazosin (0.3 μM) plus atropine (1 μM) (gray bars). C and D, mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in prostates (C) and vas deferens (D) taken from P2X1-purinoceptor knockout mice after the administration of no drug (open bars), prazosin (0.3 μM) (solid bars), and prazosin (0.3 μM) plus atropine (1 μM) (gray bars). Bars represent mean force ± S.E.M. (n = 6). P values determined by a two-way repeated-measures of ANOVA represent the probability of the drug treatment causing a significant change. **, P < 0.01; ***, P < 0.001; solid bar versus control calculated by Bonferroni post-tests. ††, P < 0.01; †††, P < 0.001; gray bars versus control calculated by Bonferroni post-tests.

Fig. 5.

Mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in the prostate after the administration of prazosin (0.3 μM) (open bars) and prazosin (0.3 μM) plus suramin (30 μM) (solid bars) (A) and no drug (open bars), prazosin (0.3 μM) plus atropine (1 μM) (solid bars) and prazosin (0.3 μM) plus atropine (1 μM) plus suramin (30 μM) (gray bars) (B). Bars represent mean force ± S.E.M. (n = 5–6). P values determined by a two-way repeated-measures of ANOVA represent the probability of the drug treatment causing a significant change. ***, P < 0.001; solid bar versus control calculated by Bonferroni post-tests. †††, P < 0.001; gray bar versus control calculated by Bonferroni post-tests.

Fig. 6.

Mean contractile responses to electrical field stimulation (0.5 ms, 60 V, 1–20 Hz, 10-s pulses) in prostates (A) and vas deferens (B) taken from α_1A-adrenoceptor knockout mice in the absence (open bars) and presence of suramin (30 μM) (solid bars). Bars represent mean force ± S.E.M. (n = 6). P values determined by a two-way repeated-measures of ANOVA represent the probability of the drug treatment causing a significant change. *, P < 0.05; ***, P < 0.001; solid bar versus control calculated by Bonferroni post-tests.

Fig. 7.

Representative traces of the contractile responses to electrical field stimulation (0.5 ms, 60 V, 10 Hz, 10-s trains) in isolated preparations of prostate and vas deferens from wild-type mice in the absence and presence of prazosin (0.3 μM), prazosin (0.3 μM), and suramin (30 μM) or prazosin (0.3 μM) and atropine (1 μM). Bars indicate period of electrical field stimulation (10 s). Traces are representative of six experiments.

Fig. 8.

Normalized mean log concentration response curves to acetylcholine of prostates before and after the administration of atropine (1 μM) (A) and prazosin (0.3 μM) (B). Bars represent mean force ± S.E.M. (n = 6). P values determined by a two-way repeated-measures of ANOVA represent the probability of a significant interaction between concentration and treatment.