Beta Adrenergic Receptor Stimulants

As stated earlier there are two types of beta-reeeptors, viz Pj and Pj. Agents that stimulates P2-receptors seleetively are very effective in relaxing the smooth muscles of the bronchi and uterus. They are, therefore, useful in asthma and in the management of rmcomplicated premature laboru in the trimester of pregnancy. 

These are also known as the P-adrenergic receptor agonists. 

A few typical examples are as stated below Salbutamol Terbutaline Pirbuterol hydrochloride Salmetrol xinafoate  

3-Benzenedimethanol, a -[[(l, 1-dimethylethyl) amino] methyl]-4-hydroxy- a. -[ tert-Butylamino) methylj-d-hydroxy-w-xylene-a-a -diol BP  

Salbutamol is used as a bronchodilator. Its bronchodilating property being relatively more marked and pronounced than its effect on the heart. 

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The molecular basis of this synergy may be manifest at the level of genetic expression. Thus, beta-adrenergic receptor stimulation by NE results in gene expression, as discussed previously and shown in Figure 7—4. However, in the presence of... 

Prinz M, Hausler KG, Kettenmann H, Hanisch U (2001) beta-adrenergic receptor stimulation selectively inhibits IL-12p40 release in microglia. Brain Res. 899 264-270. 

Reinelt H, Radermacher P, Kiefer P, et al. Impact of exogenous beta-adrenergic receptor stimulation on hepatosplanchnic oxygen kinetics and metabolic activity in septic shock. Crit Care Med 1999 27 325-331. 

Pike, L.J. and Lefkowitz, R.J. (1981) Correlation of beta-adrenergic receptor-stimulated [3H]GDP release and adenylate cyclase activation. /. Biol. Chem. 256 2207-2212. 

Beta Blocker Glass of drugs that compete with beta-adrenergic receptor-stimulating agents. 

One of the few examples of decreased susceptibility among elderly is the effect of catecholamines on the heart. There is a down-regulation of beta-adrenergic receptors and a reduced response to beta-adrenergic stimulation (Turnheim 1998). This results in decreased effect of betablockers on heart rate and stroke volume. In the elderly betablockers may be less effective than other drugs against hypertension and they should not be considered appropriate for first-line therapy of uncomplicated hypertension in the elderly (Grossman and Messerli 2002). 

Atenolol stimulation of arteriolar contraction Beta-adrenergic receptor anatagonist, reduces cardiac output... 

MecHanism of Action A sympathomimetic that directly stimulates alpha-adrenergic and beta-adrenergic receptors. Therapeutic Effect Produces vasoconstriction of respiratory tract mucosa shrinks nasal mucous membranes reduces edema and nasal congestion. 

These are the agents which block the action of sympathetic nerve stimulation and circulating sympathomimetic amines on the beta adrenergic receptors. At the cellular level, they inhibit the activity of the membrane cAMP. The main effect is to reduce cardiac activity by diminishing (3 receptor stimulation in the heart. This decreases the rate and force of myocardial contraction of the heart, and decreases the rate of conduction of impulses through the conduction system. They are classified as in table 3.3.2. 

Epinephrine stimulates me beta-adrenergic receptors in me bronchioles, which in turn activate membrane-bound adenylate cyclase to synthesize more cyclic AMP, whereas theophylline inhibits the activity of phosphodiesterase, conserving the previously synthesized cyclic AMP. 

Harmon EB, Porter JM, Porter JE (2005) Beta-adrenergic receptor activation in immortalized human urothelial cells stimulates inflammatory responses by PKA-independent mechanisms. Cell Commun. Signal. 3 10. 

The putative role of PKA activation after beta-1 adrenergic receptor stimulation with xamoterol was further confirmed by the finding that both atenolol and H89 completely abolished protection (Robinet et al. 2005). These workers also showed that, besides PKA, transduction mechanisms following beta-1-adrenergic receptor stimulation, also involved PI-3K and PKC, with PKA activation occurring prior to PKC. 

Pure Gs that has been incorporated into phospholipid vesicles exhibits a very low GTPase activity, ranging from 0.02 to 0.05 mol hydrolyzed per min per mol of Gs [31], Co-incorporation into these vesicles of pure beta-adrenergic receptors increases this activity by a factor of 2-3 to 0.05-0.1 mol of GTP hydrolyzed per min per mol of Gs. Stimulation of the receptor with a beta-adrenergic agonist (isoproterenol) results in a further increase in GTP hydrolysis to rates of ca 1.0 mol of GTP hydrolyzed per min per mol of Gs [31,32],... 

Lindley SE, Lookingland KJ, Moore KE (1990b) Dopaminergic and beta-adrenergic receptor control of alpha-melanocyte-stimulating hormone secretion during stress. Neuroendocrinology 52 46-51. 

Kohm AP, Sanders VM (2001) Norepinephrine and beta 2-adrenergic receptor stimulation regulate Cd4+ T and B lymphocyte func-tiorr in vitro and in vivo. Pharmacol Rev 53 487—525. 

Bernardin G, Strosberg AD, Bernard A, et al. Beta-adrenergic receptor-dependent and -independent stimulation of adenylate cyclase is impaired during severe sepsis inhumans. Intensive Care Med 1998 24 1315-1322. 

Albuterol selectively stimulates beta-adrenergic receptors in the lungs causing relaxation of bronchial smooth muscles, which in turn relieves bronchospasm and reduces airway resistance. The selective beta2-adrenergic stimulants cause bronchodilation without cardiac acceleration. Metaproterenol and terbutaline are available in tablet form, and terbutaline is also available for subcutaneous injection. Metaproterenol and albuterol are available in metered-dose inhalers. 

Two different kinases are involved in phosphorylating beta-adrenergic receptors. Protein kinase A is positively regulated by cyclic AMP and is stimulated by substances that activate adenylate cyclase. Beta-adrenergic receptor kinase (BARK) is related functionally to rhodopsin kinase and may be important for regulating neural transmission (see Figure 52). A cytosolic protein, beta-arrestin, interacts with the BARK-phosphorylated receptors and disrupts the activation of Gs by the beta receptor. 

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