Properties of Inhibitory Junctional Transmission in Smooth Muscle of the Guinea Pig Lower Esophageal Sphincter

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Author(s)

Abstract

Inhibitory neurotransmission in guinea pig lower esophageal sphincter (LES) muscles was investigated by using electrophysiological methods. Transmural nerve stimulation (TNS) initiated an inhibitory junction potential (i.j.p.); the amplitude increased 35% by atropine (10<SUP>-6</SUP> M) and converted to a muscarinic excitatory junction potential (e.j.p.) by apamin (10<SUP>-7</SUP> M) plus N<SUP>ω</SUP>-nitro-L-arginine (L-NNA, 10<SUP>-5</SUP> M). In atropinized tissue, the i.j.p. amplitude was reduced 58% by guanethidine (5×10<SUP>-6</SUP> M), 41% by L-NNA (10<SUP>-5</SUP> M), 57% by suramin (10<SUP>-4</SUP> M), and it was abolished by apamin (10<SUP>-7</SUP> M), suggesting that this potential was produced by ATP and nitric oxide (NO) released from adrenergic and nitrergic nerves, respectively, through the activation of Ca<SUP>2+</SUP> -sensitive K<SUP>+</SUP> channels. Hyperpolarizations produced by ATP and NO were inhibited by apamin. The i.j.p. amplitude was reduced after desensitizing the membrane with ATP. In atropinized tissue, TNS produced a relaxation that was reduced 15% by guanethidine (5×10<SUP>-6</SUP> M), 50% by L-NNA (10<SUP>-5</SUP> M), and 30% by apamin (10<SUP>-7</SUP> M). Thus the LES receives cholinergic excitatory and adrenergic and nitrergic inhibitory innervations; the latter two components contribute evenly to the i.j.p. generation. The relaxation is mainly produced by NO in a membrane potential-independent way.

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 48(6), 457-465, 1998-12-01

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  31

Cited by:  2

Codes

  • NII Article ID (NAID)
    10008305878
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    0021521X
  • NDL Article ID
    4652909
  • NDL Source Classification
    ZS8(科学技術--医学--解剖学・生理学・生化学)
  • NDL Call No.
    Z53-D40
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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