Nicotinic cholinergic stimulation increases cyclic GMP levels in vertebrate skeletal muscle

Abstract

CYCLIC GMP seems to be an intracellular second messenger for certain actions of acetylcholine at muscarinic receptors (for a review, see ref. 1). For example, previous studies have provided evidence that activation of muscarinic, but not of nicotinic, cholinergic receptors leads to an increase in the level of cyclic GMP in many tissues^2–8, including smooth muscle^3–5. Also, it has been demonstrated that contraction of cross-striated muscle fibres of the giant barnacle elicited by nerve stimulation is associated with an increase in the level of muscle cyclic GMP⁹. These observations prompted us to determine whether a similar cyclic GMP increase is associated with contractile activity in vertebrate skeletal muscle. We report here that activation of a nicotinic cholinergic synapse raises the level of cyclic GMP in frog skeletal muscle. As in smooth^4,5 and in barnacle⁹ muscle, this cyclic GMP increase in vertebrate skeletal muscle is a consequence of a neurotransmitter-induced depolarisation of the muscle membrane.