Is cyclic guanosine monophosphate the internal 'second messenger' for cholinergic actions on central neurons?
The most consistent effects produced by intracellular injections of guanosine 3',5'-cyclic monophosphate (cGMP) (but not 5'-guanosine 5'-monophosphate in spinal motoneurons of cats are a rise in membrane conductance, acceleration in time course of spike potentials, and accentuation of the post-spike hyperpolarization. Associated changes in resting potential are smaller, less constant, and more often in the depolarizing than hyperpolarizing direction, cGMP tends to increase electrical excitability but reduces excitatory post-synaptic potential amplitudes. Most of the effects of intracellular cGMP are quite different from, or indeed opposite to, those of either extra- or intracellular applications of acetylcholine and therefore not consistent with the proposal that cGMP is the internal mediator of muscarinic actions.
D000109:Acetylcholine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D006152:Cyclic GMP / Q000502:physiology*; D005071:Evoked Potentials / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009046:Motor Neurons / Q000187:drug effects*; D010277:Parasympathomimetics / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects
D010277:Parasympathomimetics; D006152:Cyclic GMP; D000109:Acetylcholine