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Antagonism by SR 48692 of mechanical responses to neurotensin in rat intestine
Author(s) -
Mulè F.,
Serio R.,
Postorino A.,
Vetri T.,
Bonvissuto F.
Publication year - 1996
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.1476-5381.1996.tb15216.x
Subject(s) - neurotensin , medicine , endocrinology , duodenum , isometric exercise , receptor , carbachol , chemistry , antagonism , biology , anatomy , neuropeptide
1 The effects of SR 48692 on neurotensin (NT)‐induced mechanical responses were investigated in rat duodenum and proximal colon by use of isometric, isovolumic preparations. 2 SR 48692 inhibited the relaxant responses to NT in duodenal circular and longitudinal muscle. It also antagonized the NT‐induced contractile effects in duodenal circular muscle and in proximal colon (both muscular layers). 3 From Schild analysis the pA 2 value for SR 48692 was 8.2 in tissues where NT induced relaxant effects and 7.5 in tissues where NT induced contractile effects and the slope of the regression line was not significantly different from unity, indicating competitive antagonism. 4 SR 48692 did not antagonize the duodenal relaxant effect induced by noradrenaline and the contractile response to carbachol or substance P in duodenum and colon. 5 Our results demonstrate that SR 48692 selectively antagonizes the mechanical actions of NT in rat intestine and confirm the existence of specific NT receptors. Receptors that subserve a relaxant effect seem to be related, but not identical, to those that mediate contractile effects.