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Sodium‐dependence of the non‐specific desensitization of the guinea‐pig ileum induced by acetylcholine and histamine
Author(s) -
Aboulafia J.,
Capocci H.,
Paiva A.C.M.,
Paiva T.B.
Publication year - 1987
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1987.tb08964.x
Subject(s) - tonic (physiology) , acetylcholine , histamine , chemistry , endocrinology , medicine , desensitization (medicine) , ileum , isometric exercise , prostaglandin e2 , guinea pig , biology , biochemistry , receptor
1 The isometric maximal responses of the guinea‐pig ileum to acetylcholine and to histamine (but not those to prostaglandin E 2 and to high K + ) exhibited a secondary transient increase in tonus during the tonic component of the contraction. 2 After desensitizing treatment with acetylcholine or histamine, the isometric responses to either agonist showed decreased phasic and enhanced tonic components, whereas both components of the response to prostaglandin E 2 were markedly depressed. 3 During the desensitizing treatment the degree of desensitization went through a maximum that coincided with the occurrence of the secondary tonic increment. 4 In low‐Na + medium, or in ouabain‐treated tissues, the responses to the three agonists were similar to the respective responses in the desensitized state. 5 It is concluded that the non‐specific desensitization is due to changes in Na + translocation and that the increased tonic component of the isometric response is due to a reduced Na + gradient across the cell membrane and consequent increase in Ca 2+ loading.