[Tetrodotoxin effect on spontaneous and evoked impulse activity of leech Retzius neurons]

Investigation into the Retzius neuron response to synaptic low-, medium-, and high-frequency stimulation under the block of the TTX-sensitive sodium inflow channels, was performed in leeches. The TTX block affected the spontaneous unit activity and not the evoked activity, it altered the responses to low-frequency stimulation (sensitisation) and eliminated the responses to high-frequency activation (habituation). The findings suggest the fundamental plastic properties of the Retzius neurons to depend on functional characteristics of the TTX-sensitive sodium channels.