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Actions of indomethacin and prostaglandins on neuroeffector transmission in the dog trachea
Author(s) -
Ito Yushi,
Tajima Kikuo
Publication year - 1981
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1981.sp013915
Subject(s) - sucrose gap , tetrodotoxin , prostaglandins f , propranolol , chemistry , excitatory postsynaptic potential , membrane potential , electrophysiology , atropine , neuromuscular transmission , biophysics , medicine , endocrinology , prostaglandin , biology , biochemistry , receptor
Neuro‐effector transmission in the smooth muscle layer of the dog trachea was studied in vitro using the micro‐electrode and double sucrose gap methods. 1. Electrical field stimulations with short duration (50‐100 μsec) applied to the whole tissue produced an excitation of the intrinsic nerves, and evoked excitatory junction potentials (e.j.p.s) followed by twitch tension development and subsequent long lasting relaxation of the smooth muscle tissue. 2. The effects of field stimulations were abolished by tetrodotoxin (2 × 10 −7 m ), and atropine (1·7 × 10 −5 m ) selectively blocked both the e.j.p. and twitch tension. On the other hand, propranolol (1·9 × 10 −5 m ) suppressed the generation of the prolonged relaxation evoked by the field stimulations. 3. E.j.p.s recorded by the double sucrose gap method showed gradual and continuous reduction in amplitude during prolonged exposure in Krebs solution (1‐2 hr), and there were no changes in the membrane potential or in the input membrane resistance. 4. With application of indomethacin (10 −5 m ), a gradual and continuous reduction in the amplitude of e.j.p. was no longer observed, and (after the initial increase in the amplitude) e.j.p.s with a constant amplitude were obtained during 1‐1·5 hr. Indomethacin (10 −5 m ) modified neither the resting membrane potential nor the input membrane resistance of smooth muscle cells. 5. After pre‐treatment with indomethacin, low concentrations (10 −11 ‐10 −8 m ) of prostaglandin E 1 or E 2 (PGE series) markedly suppressed the amplitude of e.j.p. with no changes in the resting membrane potential or in the input membrane resistance. 6. During the repetitive field stimulation at the stimulus frequency of 0·1‐1 Hz, the amplitude of the e.j.p.s was gradually reduced (the depression process). The depression was not affected by applications of prostaglandins, indomethacin or α‐ and β‐adrenoceptor blockers. 7. These results indicate that in the dog tracheal smooth muscles, the endogenous PGE series may play an important role in feed‐back inhibitory mechanisms, at the nerve terminals related to acetylcholine release.