Imidazoline receptors in relaxation of acetylcholine-constricted isolated rat jejunum.
Journal Title: Pharmacological Reports - Year 2006, Vol 58, Issue 5
Abstract
Since 20 years the concept of specific imidazoline receptors has remained controversial. The problem with imidazoline receptors is mostly due to their functional similarity to alpha-adrenoceptors. In this work, a pharmacodynamic model of isolated rat jejunum longitudinal muscle strips constricted with acetylcholine (Ach) was applied to separate functional properties of the two types of receptors. Relaxation of the preparation was measured as a function of concentration of 2-(benzofuranyl)-2-imidazoline (2-BFI), a specific imidazoline I(2) receptor ligand, cirazoline, a potent I(2) receptor ligand and alpha(1)-adrenoceptor agonist, phenylephrine, an agonist of alpha(1)-adrenoceptor, moxonidine, a ligand of I(1) receptor, efaroxan, a ligand of I(3) receptor and 5-bromo-6-(imidazoline-2-yl-amino)quinoxaline (UK14304), an agonist of alpha(2)-adrenoceptor. Next, the effects of a series of imidazoline-and/or alpha-adrenoceptor-binding drugs (prazosin, yohimbine, RS79948, RX821002, idazoxan and efaroxan) on the relaxation of the Ach-constricted rat jejunum strips, induced by 2-BFI, cirazoline or phenylephrine, were studied. The obtained results demonstrate the involvement of the postsynaptic imidazoline receptors in rat jejunum motility. These receptors are of I(2) subtype and are linked to alpha-adrenoceptors of the predominantly alpha(1) subtype. The alpha(1) receptors dominate functionally over the I(2) in the isolated rat jejnum. The proposed model might be useful in search for more specific new drugs.
Authors and Affiliations
Wioletta Kaliszan, Jacek Petrusewicz, Roman Kaliszan
Keywords
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