THE EFFECT OF SPIKE ACTIVITY VERSUS SYNAPTIC ACTIVATION ON THE METABOLISM OF RIBONUCLEIC ACID IN A MOLLUSCAN GIANT NEURONE

—Previous experiments on a giant neurone (R2) from Aplysia californica have shown that a prolonged electrical stimulation of ganglionic nerves, strong enough to elicit post-synaptic spikes in the giant neurone, caused a marked increase in the uptake of labelled nucleosides into the neuronal RNA. The results described in the present paper very strongly indicate that these effects of synaptic activation were not due to the discharge of spikes in the giant neurone itself. Spikes which were directly elicited in the giant neurone by current pulses injected into the cell through an intracellular microelectrode had no significant effect on RNA labelling. Weak stimulation of ganglionic nerves, eliciting post-synaptic potentials but few spikes in the giant neurone, produced a small but significant increase of RNA labelling.