Abstract
It is known that papaverine and isoprenaline stop the spontaneous spike discharge, usually with some hyperpolarization (1-6). The action of β-adrenergic stimulants is thought to be related to the ability of these drugs to increase the intracellular level of cyclic 3', 5'-adenosine monophosphate (cyclic 3', 5'-AMP) in the smooth muscles. In the isolated smooth muscle, catecholamine-induced relaxation is thought to be preceded by a rapid rise in cyclic 3', 5'-AMP concentration. Although exogeneously applied cyclic 3', 5'-AMP does not gain access to the intracellular fluid in significant amount (7), the N6, 2'-0-dibutyryl derivative, dibutyryl cyclic adenosine monophosphate (dibutyryl cyclic AMP) has a clear action on the rat intestinal smooth muscle (8). The different effects of the nucleotides may be due to possibly increased entry into cells and a greater resistance to hydrolysis by addition of dibutyryl groups to cyclic AMP. In this paper, mode of action of isoprenaline, dibutyryl cyclic AMP and papaverine has been compared with each other.
