Smooth muscle adrenoreceptors effects

This can be accomplished either by reducing the load on the heart, or by lowering systemic venous and arterial pressure (nitrates and nitrites), or by partial suppression of adrenergic innervation of the heart (j3-adrenoreceptors), or by suppressing calcium ion transport in myocardial cells since the contraction of smooth muscles vessels is controlled by the concentration of calcinm ions in the cytoplasm (Ca channel blockers). The resulting effect of the aforementioned drngs is that they reduce the need for oxygen in the heart. 

Isoxsuprine HCl is a p-agonist with a slight selectivity for the P2" adrenoreceptors. However, a considerable portion of the vasodilator actions is attributable to a non-selective depression of vascular smooth muscles. It is considered to be possibly effective in Raynaud s disease, thromboangilitis daliterans, obliterative arteriosclerosis, and cerebrovascular insufficiency. In the management of premature labor, it has been superseded by more selective p-agonists [1]. 

Beta2 adrenoreceptor stimulants cause bronchodilation by acting on adrenoreceptors in bronchial smooth muscle. Although they are selective for 2 receptors these drugs do have some affect on cardiac Pi receptors. Cardiac side effects are not usually a problem at therapeutic doses, but could be if a patient decided to increase the dose above that recommended. 

Other intracorporal agents used to induce penile erections include papaverine, a drug with a relaxant effect on smooth muscle, and phentolamine, an a-adrenergic receptor blocker. Yohimbine, an a2-adrenoreceptor antagonist, enhances noradrenergic neurotransmission and may improve erectile dysfunction via adrenergic system activation. 

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