Imidazoline-1 receptors

The imidazoline receptor is a hypothetical receptor for a subgroup of a2 adrenergic agonists, which are characterized by their imidazoline structure (e.g. moxoni-dine). So far, there is no proof of the existence of imidazoline receptors. 

Imidazoline Receptor Immediate Early Genes Immune Complexes Immune Defense Immune System Immunity... 

Holt A, Wieland B, Baker GB. 2004. Allosteric modulation of semicarbazide-sensitive amine oxidase activities in vitro by imidazoline receptor ligands. Br J Pharmacol 143 495. 

Another, new group of compounds act via the same central mode of action the imidazoline receptor agonists. The central regulation of sympathetic tone in the medulla oblongata is sensitive not only to 2-adrenoceptors but to so called imidazoline receptors as well. Two drugs with high affinity towards... 

The discovery of the centrally acting imidazoline receptor stimulants moxonidine and rilmenidine theoretically offers the same haemodynamic advantages as the a 2-adrenoceptor agonists. However, it may be hoped that their profile of side-effects is more favourable, owing to their lower affinity for... 

Idazoxan is an imidazoline compound developed to be a potent and highly selective Oj-adrenoceptor antagonist with little interaction at Oj and P adrenoceptor or other major neurotransmitter receptors. However, like many of the imidazolines that show high affinity for adrenoceptors, idazoxan has equal or higher affinities for the recently identified imidazoline receptors. Imidazoline receptors have been shown to be present in many tissues, including human brain [De Vos et al. 1994], and have been hypothesized to be involved with the regulation of blood pressure and possibly norepinephrine release [Ernsberger et al. 1990]. 

De Vos H, Bricca G, De Keyser J, et al Imidazoline receptors, non-adrenergic idazoxan binding sites and a2-adrenoceptors in the human central nervous system. Neuroscience 59 589-598, 1994... 

Thus, studies of clonidine and methyldopa suggest that normal regulation of blood pressure involves central adrenergic neurons that modulate baroreceptor reflexes. Clonidine and a-methylnorepinephrine bind more tightly to a2 than to adrenoceptors. As noted in Chapter 6, a2 receptors are located on presynaptic adrenergic neurons as well as some postsynaptic sites. It is possible that clonidine and -methylnorepinephrine act in the brain to reduce norepinephrine release onto relevant receptor sites. Alternatively, these drugs may act on postsynaptic a2 adrenoceptors to inhibit activity of appropriate neurons. Finally, clonidine also binds to a nonadrenoceptor site, the imidazoline receptor, which may also mediate antihypertensive effects. 

At therapeutic doses, these drugs are associated with some troublesome but relatively minor side effects including dry mouth, dizziness, and sedation. The incidence of sedation seems to be related to these drug s alpha-2 stimulatory effects. Hence, agents that are more selective for imidazoline receptors may seem better tolerated because patients are more alert and have less psychomotor slowing.104... 

Kaaja R, Manhem K, Tuomilehto J. Treatment of postmenopausal hypertension with moxonidine, a selective imidazoline receptor agonist. IntJ Clin Pract Suppl. 2004 139 26-32. 

Imidazoline receptors II and 12 are GPCRs. II agonists are hypotensive. I-Rs are involved in hypertension, diabetes mellitus and mood disorder pathologies. 

Excessive actions on alpha 2 receptors and/or on imidazoline receptors... 

Zhu QM, Lesnick JD, Jasper JR, et al. a2A Adrenoceptors, not Il-imidazoline receptors, mediate the hypotensive effects of rilmenidine and moxonidine in conscious mice. In vivo and in vitro studies. Ann N Y Acad Sci 1999 881 287-289. 

Urban R, Szabo B, Starke K. Is the sympathoinhibitory effect of rilmenidine mediated by a2 adrenoceptors or imidazoline receptors J Pharmacol Exp Ther 1994 270 572-578. 

Bousquet P, Feldman J. Drugs acting on imidazoline receptors a review of their pharmacology, their use in blood pressure control and their potential interest in cardioprotection. Drugs 1999 58 799-812. 

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