Further evidence of the role of cyclic AMP as a mediator of the depressant effects of beta-adrenoceptor agonists and phosphodiesterase inhibitors on slow-contracting mammalian skeletal muscles.

The depressant effects of beta-adrenoceptor agonists and phosphodiesterase inhibitors on contractions of slow-contracting mammalian skeletal muscles are associated with increased muscular cyclic AMP levels. A strong correlation was found to exist between the percentage depression of contraction and the percentage increase in cyclic AMP level, irrespective of the drug used and regardless of the mechanism of cyclic AMP production. The results strongly support the mediatory role of cyclic AMP in the depressant effects of beta-adrenoceptor agonists and phosphodiesterase inhibitors on slow-contracting mammalian skeletal muscle contractions.