Influence of acidification on biphasic contractile response of guinea pig vas deferens to electrical field stimulation.
The phasic contraction of the isolated guinea pig vas deferens induced by adenosine 5'-triphosphate (ATP) 1mM was significantly augmented by acidification of bathing solution induced by administration of hydrochloric acid (HCL) 10mM (pH = 6.87 +/- 0.015 (n = 5); mean +/- S.E.), while the tonic contraction induced by norepinephrine (NE) 10microM was significantly depressed by HCl 10mM. The contractile response to ATP 1mM was markedly potentiated in the presence of NE 10 microM. The potentiated contractile response to ATP 1mM in the presence of NE 10microM was significantly augmented by HCl 1mM or 10mM. The potentiating ratio of the contraction induced by ATP 1mM in the presence of NE 10microM to that induced by ATP 1mM alone was almost unaffected by the administration of HCl. Electrical field stimulation (EFS) produced a biphasic contractile response of the isolated guinea pig vas deferens; viz. the first rapid phasic contractile response and the second slow maintained tonic contractile response. The phasic contractile response to EFS was significantly augmented by HCl 10mM. These results may indicate that acidification of the medium potentiates the neurochemical transmission between the nerve terminals and the smooth muscle of vas deferens via sensitization of P2X (presumably P2X1 or P2X2) receptors existing in the smooth muscle.
Nakanishi
H
H
Department of Pharmacology, Fukushima Medical College, Japan.
Matsuoka
I
I
Ono
T
T
Kimura
J
J
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D006168:Guinea Pigs; D006851:Hydrochloric Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects; D014649:Vas Deferens / Q000187:drug effects*
D013566:Sympathomimetics; D000255:Adenosine Triphosphate; D006851:Hydrochloric Acid; D009638:Norepinephrine