Differential effects of pertussis toxin on muscarinic responses in isolated atria and smooth muscle

Publisher Website
Google Scholar
Abstract
1 The effect of pretreatment with pertussis toxin has been studied on responses to muscarinic agonsits in guinea-pig atria and smooth muscle in vitro. 2 48 h after a single intravenous injection of pertussis toxin (3.2-100 .mu.g .cntdot. kg-1), muscarinic receptor-mediated negative inotropic responses in the atria were inhibited in a dose-dependent manner, with complete abolition of responses occurring after administration of 100 .mu.g .cntdot. kg-1. 3 In contrast, there was no effect on atrial positive inotropic responses to isoprenaline. In addition, no effect was observed on contractile responses to carbachol and pilocarpine in the ileum, trachea, oesophageal muscularis mucosae and urinary bladder, either in terms of potency or maximal response, at all dose levels of pertussis toxin studied. 4 It is concluded that muscarinic receptors in the atria, but not smooth muscle, are probably coupled to the inhibitory regulatory protein N1, which is functionally inactivated by pertussis toxin. The differences in coupling between atrial and smooth muscle muscarinic receptors provide further evidence for muscarinic receptor heterogeneity in these two tissues.

This publication has 27 references indexed in Scilit: