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EFFECT OF EXTRACELLULAR pH ON CONTRACTILE RESPONSES OF THE GUINEA‐PIG VAS DEFERENS
Author(s) -
Nakanishi Hironori,
Matsuoka Isao,
Ono Tomoyuki,
Kimura Junko
Publication year - 1999
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1046/j.1440-1681.1999.02984.x
Subject(s) - vas deferens , tonic (physiology) , medicine , endocrinology , stimulation , muscle contraction , extracellular , contraction (grammar) , chemistry , biology , biochemistry
1. Effects of changing the pH of the bathing solution (7.0, 7.4 and 7.8) on the contractile response of the guinea‐pig isolated vas deferens to ATP, noradrenaline (NA) and ATP in the presence of NA or electrical field stimulation (EFS) were investigated. 2. Low pH tended to augment the phasic contractile response to ATP (0.01–1 mmol/L), while high pH significantly reduced the contractile response to ATP. In contrast, low pH depressed the tonic contractile response to NA (0.1–10 μ mol/L), while high pH augmented the response to NA. The contractile response to 1 mmol/L ATP was markedly potentiated in the presence of 0.1–10 μmol/L NA. The potentiated contractile response to ATP in the presence of NA was unaffected by changes in pH. 3. Electrical field stimulation produced a biphasic contractile response. Low pH enhanced the initial rapid phasic contractile response to EFS, while high pH depressed the response. In contrast, the second slow tonic contractile response to EFS was unaffected by changes in pH. 4. These findings may indicate that the phasic contractile response to EFS is mainly caused by ATP while the tonic contractile response is a synergistic response to ATP and NA concomitantly released from sympathetic nerve terminals.