Relaxation cAMP contributing

Figure 9.7 Effects of cAMP contributing to relaxation. AC, adenylate cyclase DG, diacyl glycerol G, guanosine nucleotide regulatory protein IP3, Inositol trisphosphate, MLCK, myosin light chain kinase.

Papaverine (Fig. 26.8) is a benzoisoquinoline vasodilator that produces generalized, nonspecific arteriolar dilatation and smooth muscle relaxation. Its oral bioavailability ranges from 30 to 50%, suggesting first-pass metabolism. Increased levels of intracellular cAMP secondary to inhibition of phosphodiesterase may contribute to its vasodilatation and relaxation effects without involving nerve supply. Large doses of papaverine can cause hypotension and tachycardia. Other studies suggest that it also depresses cardiac conduction and prolongs the refractory period. 

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