Affecting Adrenergic Neurotransmission

Bretylium Tosylate. Another neuronal blinking agent is the aromatic quaternary ammonium compound bretylium tosylate (Bretylol). This agent is used as an antiarrhythmic drug. Its antiarrliythmic actions are not believed to be due to iLS neuronal blocking effects, however. This agent is dis-cu.sscd in more detail in Chapter ID. 

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Adrenergic Receptors and Drugs Affecting Adrenergic Neurotransmission... 

Griffith, R., Drugs affecting adrenergic neurotransmission, in Foy s Principles of Medicinal Chemistry,D.A. andLemke, T.L., Eds., Lippincott Williams WiMns, 2002, 292. 

We first assessed whether NO affects sympathetic neurotransmission in a peripheral vascular resistance district, namely, the mesenteric arterial bed of the rat. As shown in Fig. 1 A, electrical stimulation of periarterial adrenergic nerves at 2-8 Hz for 30 sec elicited a frequency-dependent 7-73% increase in perfusion pressure (i.e., vasoconstriction). This was accompanied by a frequency-dependent increase in NE overflow (Fig. 1C), which peaked in the first 30 sec following the termination of electrical stimulation and declined over the next 5-10 min. The NO donor SNP, at 0.1 and 1 //.M, significantly depressed the vasoconstriction elicited by electrical stimulation and by the administration of phenylephrine (Fig. lA). In contrast, SNP did not modify the increase in NE overflow (Fig. 1C). These findings indicate that SNP (i.e., exogenous NO) attenuates the vasoconstricting response to sympathetic nerve stimulation by a postjunctional action. 

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