Abstract
In previous papers (1, 2) we have reported, using the taenia of the guinea pig, that isoprenaline, papaverine and dibutyryl cyclic AMP stop the spontaneous spike discharge with some hyperpolarization, when these relax the taenia, also that these drugs are without any effect on tension of the glycerinated taenia induced by ATP and Ca in sufficient concentrations to relax the taenia. Furthermore, we have observed that all of three drugs accelerate Ca-efflux in the taenia (3). These results suggest that the inhibitory actions of these three drugs may be mediated through one mechanism, though only isoprenaline induces the inhibitory response via the β-adrenergic receptors.
The β-adrenergic action is thought however to be related to the ability of the β-stimulants to increase the intracellular level of cyclic 3', 5'-adenosine monophosphate (cyclic 3', 5'-AMP) in the smooth muscles. Other recent reports (4, 5) have mentioned that papaverine inhibits phosphodiesterase and increases the amount of cyclic 3', 5'-AMP in the cells.
One of the aims in this apper is to test whether or not inhibitory actions of the β- adrenergic stimulants and papaverine are concerned with intracellular cyclic 3', 5'-AMP as well as to determine that α-adrenergicacti on is not related to cyclic 3', 5'-AMP in the cells.
