Effects of multiple spike-initiation zones in touch sensory cells of the leech

Touch sensory cells of the leech send several long-range dendritic processes to their receptive fields in the skin. Based on electrophysiological experiments, Burgin and Szczupak [Network interactions among sensory neurons in the leech, J. Comp. Physiol. A 189(2003)59–67] proposed that T-cells have two spike-initiation zones to separately process sensory and synaptic inputs.A compartmental model of the cell shows that spike-initiation zones do not necessarily need to be “hot spots” of high Na+-channel density. However, when a “hot-spot” is located close to the soma, the remaining cell membrane can be less active. In consequence, fewer Na+-channels are needed in total to reproduce the experimental data, and therefore metabolic energy is saved. In contrast, “hot spots” of high Na+-conductance located in the skin do neither lead to a better fit of the experimental data, nor to a lower total number of Na+-channels.