[Metabolic synapse. I. Effect of intracellular microinjection of 3'-5'-AMP].

Cyclic 3'-5'-AMP was injected into neurons of Helix pomatia (theta greater than 50 mu) by the current of 10(8) minus 10(9) A. This current was passed from one intracellular electrode to another by means of a photogenerator very well isolated from the ground. The injection of 3'-5'-AMP results in a depolarization and increase of the frequency of spontaneous activity. These changes continue for several seconds after the current is switched off. The intracellular injection of 5'-AMP or 5'-ATP and also extracellular application of 3'-5'-AMP by either the same or tenfold current does not change the spontaneous activity of these neurons.