Evidence of non-synaptic regulation of postpartum uterine contractility in the rat

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Myometrial tissue rings from postpartum rats (24 h after delivery) were studied in vitro by electric field stimulation, and the α12-adrenoceptor ratio was determined by a radioligand binding technique. Pregnancy-denervated uterine rings were stimulated by long-duration pulses (100 ms). The contractions were inhibited by β2-agonists (terbutaline and fenoterol) and α-antagonists (phentolamine, urapidil and yohimbine) in a concentration-dependent manner. Their effects were not altered by the adrenergic neuron-blocking agent bretylium. The α-antagonists (except phentolamine) elicited the same maximal inhibition as the β2-agonists. Receptor assays revealed that the α12 ratio was about 2 in the measured uteri. It was concluded that the inhibitory effects of α-antagonists and β2-agonists are mediated via non-synaptic adrenoceptors of the denervated postpartum rat uterus. The same inhibitory activity could be explained by the greater amount of α-receptors. It is believed that this is the first functional proof of the existence of non-synaptic α1-adrenoceptors in smooth muscle.

Original languageEnglish
Pages (from-to)1119-1124
Number of pages6
JournalLife sciences
Issue number12
Publication statusPublished - Feb 13 1998


  • Electric field stimulation
  • Myometrium
  • Non-synaptic regulation
  • Receptor density

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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