ISSN:
1432-1912
Keywords:
Myenteric plexus
;
Presynaptic muscarine receptors
;
Acetylcholine release
;
Oxotremorine
;
Atropine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary 1. The effects of oxotremorine and atropine on the release of acetylcholine from longitudinal muscle strips of the guinea-pig ileum stimulated at frequencies between 0.1 and 3 Hz in the presence of eserine were investigated. In control experiments the acetylcholine output per stimulus declined with increasing frequencies of stimulation. 2. Oxotremorine inhibited the release of acetylcholine in a concentration-dependent fashion. At a concentration of 10−6 M oxotremorine, the release evoked by 0.1 Hz was reduced by 54%. With increasing frequencies of stimulation the inhibitory effect of oxotremorine became smaller. 3. Atropine enhanced the output of acetylcholine evoked by electrical stimulation. In the presence of 10−8 M atropine, the concentration-effect curve for the inhibitory action of oxotremorine was shifted to the right in a parallel manner. From the dose-ratio a pA2 value for atropine against oxotremorine of 8.8 was calculated. 4. Hexamethonium (2.8×10−4 M) did not affect the modulating effects of oxotremorine or atropine on acetylcholine output. 5. It is concluded that the guinea-pig ileum myenteric plexus contains inhibitory muscarine receptors whose stimulation by oxotremorine or by liberated endogenous acetylcholine leads to a diminished output of transmitter. Atropine, by blocking these receptors facilitates acetylcholine release. Further, the results suggest that the depression of acetylcholine release per stimulus with increasing frequencies of stimulation is due to the presence of the inhibitory muscarine receptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00505045
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