Adrenergic and purinergic components in bisected vas deferens from spontaneously hypertensive rats

Abstract

1. Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens. 2. In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5-32 Hz) evoked frequency-related contractions. The neurogenic responses were biphasic, consisting of a rapid non-adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half. 3. Phasic and tonic components of the frequency-response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats. 4. The alpha1-adrenoceptor antagonist prazosin (0.1 microM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats. 5. Inhibition by alpha, beta-methylene adenosine 5'-triphosphate (alpha,beta-meATP 3 and 30 microM) was higher in both components of the contractile responses in WKY preparations than in SHR. 6. Combined alpha1-adrenoceptor and P2x-purinoceptor antagonism virtually abolished the EFS-evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 microM) after P2x-purinoceptor blockade was higher in SHR than in WKY rats. 7. These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co-participation of ATP and noradrenaline in both contractile components of the response to EFS.

Figure 1

Recordings of contractile responses (mN) evoked by EFS (40 V, 0.5 ms for 30 s, 4 Hz) in the prostatic (a) and epididymal (b) portions of rat vas deferens. Phasic (P) and tonic (T) components of the EFS contractile response are shown.

Figure 2

Frequency-response curves to EFS (40 V, 0.5 ms for 30 s, 0.5–16 Hz) in the prostatic portion of vas deferens from SHR and WKY rats. (a) Phasic and (b) tonic components of the contractile response. Results are expressed as absolute values (mN). Points are mean±s.e.mean of at least 23 experiments. SHR and WKY curves are not significantly different; two-way (strain, frequency) ANOVA with repeated measures on frequency factor.

Figure 3

Frequency-response curves to EFS (40 V, 0.5 ms for 30 s, 0.5–16 Hz) in the epididymal portion of vas deferens from SHR and WKY rats. (a) Phasic and (b) tonic components of the contractile response. Results are expressed as absolute values (mN). Points are mean±s.e.mean of 26 experiments. SHR and WKY curves diverge significantly (P<0.0001); two-way (strain, frequency) ANOVA with repeated measures on frequency factor. Vertical pairwise contrasts: ^*P<0.05, ^**P<0.01.

Figure 4

Frequency-response curves to EFS (40 V, 0.5 ms for 30 s, 0.5–16 Hz) in the epididymal portion of vas deferens in the absence (control) and presence of prazosin (0.1 μM). Phasic component in (a) WKY and (b) SHR. Tonic component in (c) WKY and (d) SHR. Points are mean±s.e.mean of six experiments expressed as a percentage of the maximal contraction (E_max) obtained in the first curve. Control and prazosin curves diverge significantly in all figures (P<0.0001); two-way (treatment, frequency) ANOVA with repeated measures on both factors. Vertical pairwise contrasts: ^*P<0.05, ^**P<0.01, ^***P<0.001.

Figure 5

Frequency-response curves to EFS (40 V, 0.5 ms for 30 s, 0.5–16 Hz) in the epididymal portion of vas deferens in the absence (control) and presence of α,β-meATP (3, 30 or 100 μM). Phasic component in (a) WKY rats and (b) SHR. Tonic component in (c) WKY rats and (d) SHR. Points are mean±s.e.mean of six experiments expressed as a percentage of the maximal contraction (E_max) obtained in the first curve. Minimal concentration values at which α,β-meATP and control curves diverge significantly: 3 μM (a,c,d), 30 μM (b). Minimal concentration values from which a concentration increase of α,β-meATP does not reduce EFS response: 3 μM (c), 30 μM (a,b,d); two-way ANOVA with repeated measures on frequency factor. Vertical pairwise contrasts: ^*P<0.05, ^**P<0.01, ^***P<0.001 control vs 3 μM and +P<0.05, ++P<0.01, +++P<0.001 3 μM vs 30 μM.

Figure 6

Frequency-response curves to EFS (40 V, 0.5 ms for 30 s, 0.5–16 Hz) in the epididymal portion of vas deferens in the absence (control) and presence of α,β-meATP (100 μM) and α,β-meATP (100 μM) plus prazosin (0.1 μM). Phasic component in (a) WKY and (b) SHR and tonic phase in (c) WKY and (d) SHR. Points are mean±s.e.mean of four experiments expressed as a percentage of the maximal contraction (E_max) obtained in the first curve. In all figures α,β-meATP vs control and α,β-meATP plus prazosin vs α,β-meATP curves diverge significantly (P<0.0001); two-way (treatment, frequency) ANOVA with repeated measures on both factors. Vertical pairwise contrasts: ^*P<0.05, ^**P<0.01, ^***P<0.001 α,β-meATP vs control and +P<0.05, ++P<0.01, +++P<0.001 α,β-meATP plus prazosin vs α,β-meATP.