Blood vessel relaxation

Back in 1913, adrenaline was found to cause either constriction or relaxation of blood vessels, depending on the anatomical site. Scientists correctly concluded that there must be two classes of adrenergic receptors. These are termed alpha and beta adrenergic receptors. When adrenaline hits the alpha-type receptor, blood vessel constriction results at the beta-type receptor, blood vessel relaxation results. Thus, adrenaline and noradrenaline are nonspecific agonists (activators) at adrenergic receptors. 

Papaverine also has minimal narcotic properties. However, it does have vasodilator (blood vessel relaxant) properties, and because of this property it has been employed for both cognition enhancement and erectile dysfunction. 

Another group of drugs that relax heart muscle are the calcium-channel blockers. One example is nifedipine, shown in Figure 14.46. Muscle contraction is initiated as a nerve impulse signals calcium ions to enter muscle cells. As their name implies, calcium-channel blockers inhibit the flow of calcium ions into muscles, thereby inhibiting muscle contraction. The heart rate slows down, and muscles of blood vessels relax and dilate, lowering blood pressure. 

Chen et al. [175] synthesized tacrine-flurbiprofen hybrids and tacrine-flurbiprofen-nitrate trihybrids. These compounds displayed comparable or higher cholinesterase inhibitory activity relative to the bivalent hybrids, released NO, exerted blood vessel relaxative activity, and showed significant Ap inhibitory effects. 

Dopamine, Renal and other splarx hnic blood vessels Relaxes (reduces resistance)... 

The existence of two different adrenergic receptors was first suggested by Ahlquist (1948) Those responses evoked most readily by noradrenaline (norepinephrine), less by adrenaline 7.43), still less by isoprenaline 12.44) and least by A -/-butylnorepinephrine are credited to a-receptors those for which this sequence runs in the reverse direction are credited to jS-receptors. Typical a-responses are constriction of blood-vessels, stimulation of the uterus, relaxation of the intestine. Typical jS-responses are dilatation of blood-vessels, relaxation of the uterus, stimulation of muscle glycogenolysis, production of tachycardia (Levy and Ahlquist, 1961). 

In mammals and other vertebrates, nitrogen monoxide plays several important roles. For example, it acts as agaseous mediator in producing such responses as dilation of blood vessels, relaxation of smooth muscle, and inhibition of platelet aggregation, and it acts as a neurotransmitter in the central nervous systems. In certain cells of the immune system it is converted to the peroxynitrite ion ("0-0-N=0), which has activity against pathogens. 

Nitric oxide (NO) is an important messenger molecule regulating the biological processes, viz., blood vessel relaxation, neuronal ceU-to-ceU communication, and immune function (Szabo, 1996 Ahanchi et al., 2007). Its level is significandy altered in serum as weU as in exhaled breath during oxidative stress, airway inflammation, and various diseases such as asthma and primary cilia dyskinesia (Nevin and Broadley, 2002 Zitt, 2005). Therefore, the measurement of NO is essential in human physiology. Commercially... 

---