cyclic guanosine monophosphate (cGMP), a substance that mediates the action of certain hormones in a manner similar to that of cyclic adenosine monophosphate. In response to the stimulation of cholinergic receptors in a parasympathetic nerve, guanylate cyclase triggers the conversion of guanosine triphosphate to cGMP with the release of various enzymes. Atropine, an anticholinergic drug, can block cholinergic stimulation by means of this process.
