A monosynaptic connection between the medial nociceptive and the Nut cell in leech ganglia

Abstract

1. In leech (Macrobdella decora) segmental ganglia, stimulation of the medial nociceptive cell (Nmed) evoked a short latency (2–3 ms) excitatory postsynaptic potential (epsp) of 1–4 mV amplitude in the Nut cell, a nearby identified neuron of unknown function. 2. The epsp's were abolished by high concentrations of Mg and enhanced by high concentrations of Ca. 3. Following intracellular injection of tetraethylammonium chloride (TEA) into the presynaptic Nmed cell, the amplitude of the epsp increased to 5–7 mV in a graded manner. 4. In contrast, no excitatory synaptic responses were obtained in the Nut cell after stimulation of the lateral nociceptive cell (Nlat). 5. These results strongly suggest the presence of a monosynaptic connection between the Nmed and the Nut cell and present more evidence that the two nociceptive cells are not identical.