Differentiation between anti- and orthodromic responses to nerve stimulation in neurons with axo-axonal synapses (Helix pomatia).

In identified neurons of Helix pomatia nerve stimulation evoked depolarizations of short latencies. The mechanisms underlying these potentials were studied by conventional electrophysiological and intracellular staining techniques. Most of the depolarizations behaved like chemically mediated postsynaptic potentials. The remaining responses can be regarded either as antidromic axonal action potentials (APs) or as electrotonic junction potentials. The differentiation between the latter alternatives and hence the identification of the axonal pathways of the impaled neurons proved to be difficult using conventional methods.