Alpha-adrenoceptor

Gobel, J., Saussy, D. L., and Goetiz, A. S. (1999). Development of scintillation-proximity assays for alpha adrenoceptors. J. Pharmacol. Toxicol. Meth. 42 237. 

Bremner,. B., Coban, B., Griffith, R Groenewoud, K. M., Yates, B. F. Ligand design for alpha] adrenoceptor subtype selective antagonists. Bioorg. Med. Chem. 2000, 8, 201-214. 

Djavan B, Chappie C, Milani S, Marberger M. State of the art on the efficacy and tolerability of alpha, adrenoceptor antagonists in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia. Urology 2004 64 1081-1088. 

J Burke, E Padillo, G Sachs, E Cragoe. (1992). Inhibitors of Na+/H+ exchange modify IOP responses to alpha adrenoceptor agonists. Invest Ophthalmol Vis Sci 33 1116. 

Ko FN, Yu SM, Su MJ, Wu YC, Teng CM. Pharmacological activity of (-)-discreta-mine, a novel vascular alpha-adrenoceptor and 5-hydroxytryptamine receptor antagonist, isolated from Fissistigma glaucescens. BrJ Pharmacol. 1993 110 882-888. 

Hilakivi, I. (1983). The role of beta- and alpha-adrenoceptors in the regulation of the stages of the sleep-waking cycle in the cat. Brain Res. 277, 109 18. 

Pellejero, T., Monti, J. M., Baglietto, J. et al. (1984). Effects of methoxamine and alpha-adrenoceptor antagonists, prazosin and yohimbine, on the sleep-wake cycle of the rat. Sleep 7, 365-72. 

Baraban, J. M., and Aghajanian, G. K. (1980) Suppression of serotonergic neuronal firing by alpha-adrenoceptor antagonists Evidence against GABA mediation. Eur. J. Pharmacol., 66 287-294. 

Subarnas A, Tadano T, Kisara K, Ohizumi Y. (1993c). An alpha-adrenoceptor-mediated mechanism of hypoactivity induced by beta-amyrin palmitate. J Pharm Pharmacol. 45(11) 1006-8. 

Q60 When a patient who is receiving atenolol is started on terazosin, there is an increased risk of first-dose hypotension. Terazosin is an alpha-adrenoceptor agonist which causes vasodilatation. 

Van Zwieten PA. Alpha-adrenoceptor blocking agents in the treatment of hypertension. In Laragh JH, Brenner BM, editors. Hypertension. Pathophysiology, diagnosis and management. 2nd ed. New York Raven Press 1995. p. 2917-36. 

Handley SL, Mithani S (1984) Effects of alpha-adrenoceptor agonists and antagonists in a maze exploration model for fear-motivated behavior. Naunyn Schmiedebergs Arch Pharmacol 327 1-5... 

Elliott HE, Jones CR, Vincent J, et al The alpha adrenoceptor antagonist properties of idazoxan in normal subjects. Chn Pharmacol Ther 36 190-196, 1984... 

Alpha-adrenoceptor antagonists inhibit the activation of a adrenoceptors by catecholamines. In the cardiovascular system these receptors are mainly located on the surface of smooth muscle cells in the walls of arteries and veins. On activation, they mediate an increase in intracellular free calcium, which induces smooth muscle contraction. Inhibition by an a antagonist causes arterial or venous vasodilatation. The postsynaptic effect is mainly mediated by ol adrenoceptors whereas o2 adrenoceptors are found on the presynaptic membranes of the sympathetic neurones. Activation of o2-adreno-ceptors results in auto-inhibition of catecholamine release. 

Alpha-adrenoceptor antagonists are used as antihypertensives and to reduce afterload in the treatment of heart failure. Urapidil and, to a lesser extent, ketanserin are used in the treatment of essential hypertension and acute perioperative hypertension. In contrast to other vasodilators urapidil does not increase intracranial pressure when given intravenously, making it preferable for use in neurosurgical interventions. The effects of the excessive catecholamine concentrations in patients with phaeochromocytoma can be treated by the non-selective ol- and o2-adrenoceptor antagonists phentolamine or phenoxybenzamine. 

Antimuscarinic drugs should never be used for mydriasis unless cycloplegia or prolonged action is required. Alpha-adrenoceptor stimulant drugs, eg, phenylephrine, produce a short-lasting mydriasis that is usually sufficient for funduscopic examination (see Chapter 9). 

ACh M, acetylcholine muscarinic receptor ctlf alpha -adrenoceptor H1 histaminei receptor 5-HT2, serotonin 5-HT2 receptor NET, norepinephrine transporter SERT, serotonin transporter. 0/+, minimal affinity +, mild affinity ++, moderate affinity +++, high affinity. 

The benefit of combining an alpha-adrenoceptor antagonist with a 5-alpha-reductase inhibitor has been assessed in men with benign prostatic hyperplasia (23). Modified-release alfuzosin was more effective than finasteride, with no additional benefit in combining the drugs. The adverse effects of alpha-blockade were postural hypotension, hypotension, headache, dizziness, and malaise the adverse effects of finasteride were ejaculatory disorders and impotence. 

In a controlled study of octreotide and midodrine (an alpha-adrenoceptor agonist) in patients with orthostatic hypotension, the pressor effect of the two drugs was synergistic (56). 

Civantos Calzada B, Aleixandre de Artinano A. Alpha-adrenoceptor subtypes. Pharmacol Res. 2001 44 195-208. 

Alpha adrenoceptors mediate contraction of the radially oriented pupillary dilator muscle fibers in the iris and result in mydriasis. This occurs during sympathetic discharge and when alpha agonist drugs such as phenylephrine are placed in the conjunctival sac. Beta-adrenoceptors on the ciliary... 

WB4101 = jV-[2-(2,6-dimethoxyphenoxy)ethyl]-2,3-dihydro-l,4-benzodioxan-2-methanamine Alpha Adrenoceptors... 

Caulfield MP, Jones S, Vallis Y, Buckley NJ, Kim GD, Milligan G, Brown DA (1994) Muscarinic M-current inhibition via G alpha q/11 and alpha-adrenoceptor inhibition of Ca2+ current via G alpha o in rat sympathetic neurones. J Physiol 477 Pt 3 415-22 Charvin N, L Eveque C, Walker D, Berton F, Raymond C, KataokaM, Shoji-Kasai Y, Takahashi M, De Waard M, Seagar MJ (1997) Direct interaction of the calcium sensor protein synaptotagmin I with a cytoplasmic domain of the alphal A subunit of the P/Q-type calcium channel. Embo J 16 4591-6... 

In recent years traditional neuroleptics, as exemplified by chlorpromazine, have been structurally modified to produce drugs with greater affinity for dopamine receptors while retaining some of their activity on other receptor systems (e.g. on alpha] adrenoceptors, 5-HT2 receptors and histamine] receptors). In the non-phenothiazine series, a high degree of specificity for the D2 receptors has been achieved with sulpiride and pimozide, with haloperidol showing antagonistic effects on the 5-HT2 and alpha] adrenoceptors in addition to its selectivity for D2 receptors. The czs-(Z) isomers of the thioxanthines are potent neuroleptics that, in addition to... 

In the phenothiazine series of neuroleptics, thioridazine has less antimuscarinic potency than chlorpromazine, but appears to be equally active as an antagonist of 5-HT2 and D2 receptors like chlorpromazine, however, it is a potent alpha] adrenoceptor antagonist. In contrast, the potent phenothiazine neuroleptic perphenazine is only slightly less selective in blocking D2 receptors than haloperidol but, unlike the latter, has a greater antagonistic effect on histamine receptors. 

Schoeffier P, Hoyer D. Interaction of the alpha-adrenoceptor agonist oxymetazoline with serotonin 5-HT1A, 5-HT1B, 5-HTlc and 5-HT1D receptors. Eur J Pharmacol 1991 196 213-216. 

The doctor is sympathetic cough is sometimes a problem for patients taking captopril she prescribes an alpha-adrenoceptor (a-adrenoceptor) antagonist, prazosin, instead. Sam has problems initially with orthostatic hypotension however, after dosage reduction, prazosin is well tolerated and Sam s BP settles at 143/87 mmHg. 

---