Cardiac alphai-adrenergic receptor stimulation: Positive inotropism and arrhythmias (part 1)

 Positive inotropism and arrhythmias (part 1)

Myocardial function is markedly modulated by the sympathetic nervous system. Besides beta-adrenergic stimulation, whose consequences and signal transduction cascade have been well studied, more recent work relates to alpha1-adrenergic stimulation. We briefly review two short term major physiological aspects of this stimulation and summarize the intracellular mechanisms that lead to an increase in mechanical activity and, under some conditions, to abnormality in electrical activity. In addition to these acute actions, alpha1-adrenergic receptors mediate several long-lived effects, including the expression of genes switched on during cell growth and which might lead to cell hypertrophy and other pathologies, aspects that are outside the scope of this review. The reader should refer to recent detailed reviews .
For 30 years alpha1-adrenergic receptors have been known to be present in the heart. Endogenous catecholamines elicit a positive inotropic response in animals as well as in humans at concentrations below those required to stimulate beta-adrenergic receptors, suggesting that alpha1-adrenergic receptors play a significant physiological role in the neuro-humoral control of myocardial contractility. Recent evidence indicates that there are various subtypes of alpha1-adrenergic receptors, all with seven transmembrane domains. Cheapest medications available online and best pharmacies offering a chance to buy birth control online click here for you to spend less time and money whenever your shop.