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. 2021 Feb;73(1):255-260.
doi: 10.1007/s43440-020-00118-x. Epub 2020 Aug 28.

Both α1B- and α1A-adrenoceptor subtypes are involved in contractions of rat spleen

Hadeel A Alsufyani  1 , P Aiden McCormick  2 , James R Docherty  3
Affiliations

Both α1B- and α1A-adrenoceptor subtypes are involved in contractions of rat spleen

Hadeel A Alsufyani et al. Pharmacol Rep. 2021 Feb.

Abstract

Background: The spleen is a reservoir for circulating blood cells, and can contract to expel them.

Methods: We have investigated the adrenoceptors involved in isometric contractions of rat spleen produced by noradrenaline (NA) and the α1-adrenoceptor agonist phenylephrine (Phe).

Results: Contractions to NA were antagonized by both the α1-adrenoceptor antagonist prazosin (10-8 M) and the α2-adrenoceptor antagonist yohimbine (10-6M), and the combination produced further shifts in NA potency. Contractions to Phe were antagonized by prazosin (10-8 M) which caused a marked parallel shift in the concentration-response curve. High non-selective concentrations of the α1D-adrenoceptor antagonist BMY7378 (10-6 M), the α1A-adrenoceptor antagonist RS100329 ((3 × 10-8 M), and the putative α1B-adrenoceptor antagonist cyclazosin (10-8 M) also produced parallel shifts in the Phe concentration-response curve. BMY7378 at the selective concentration of 3 × 10-8 M had no effect on responses to Phe, but RS100329 in the selective concentration of 3 × 10-9 M produced a marked shift in the effects of high concentrations of Phe. Hence, antagonists in concentrations that block both α1A- and α1B-adrenoceptors produce approximately parallel shifts in Phe potency.

Conclusions: Contractions of rat spleen to adrenergic agonists involve α2- and α1B-adrenoceptors, with a lesser role for α1A-adrenoceptors. This confirms the suggestion that smooth muscle contractions commonly involve multiple subtypes.

Keywords: Rat spleen; Splenic contraction; α1A-Adrenoceptors; α1B-Adrenoceptors; α1D-Adrenoceptors.

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