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Positive chronotropic and inotropic responses to BRL 37344, a beta 3-adrenoceptor agonist in isolated, blood-perfused dog atria.

Authors
  • Takayama, S
  • Furukawa, Y
  • Ren, L M
  • Inoue, Y
  • Sawaki, S
  • Chiba, S
Type
Published Article
Journal
European Journal of Pharmacology
Publisher
Elsevier
Publication Date
Feb 16, 1993
Volume
231
Issue
3
Pages
315–321
Identifiers
PMID: 8095462
Source
Medline
License
Unknown

Abstract

We investigated the chronotropic and inotropic responses to BRL 37344 (a beta 3-adrenoceptor agonist) and isoproterenol in isolated, blood-perfused dog atria. BRL 37344 (0.1-30 nmol) or isoproterenol (0.001-0.3 nmol) increased the sinus rate and contractile force dose dependently. BRL 37344 was 290 times less potent than isoproterenol to increase sinus rate and 140 times less potent to increase atrial force. Both propranolol and bisoprolol similarly inhibited the positive chronotropic and inotropic responses to BRL 37344 and isoproterenol dose dependently. ICI 118,551 (0.1 and 1 nmol) did not significantly affect the positive cardiac responses to BRL 37344 or isoproterenol. Neither imipramine nor tetrodotoxin significantly affected the positive cardiac responses to BRL 37344. These results suggest that the positive chronotropic and inotropic responses to BRL 37344 are mediated mainly by beta 1-adrenoceptors in the dog heart. It is unlikely that beta 3-adrenoceptors, as previously reported in adipose tissue or gastrointestinal smooth muscle, mediate chronotropic and inotropic responses in the normal dog heart.

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