Two forms of sensitization of the local bending reflex of the medicinal leech

Sensitization of the local bending reflex of the medicinal leech Hirudo medicinalis was studied in a semi-intact preparation in which behavioral and electrophysiological recordings were made simultaneously. 1. Sensitization of local bending could be produced in two ways: by repeated stimulation of the mechanoreceptor sensitive to pressure (the P cell), and by stimulation of the mechanoreceptor sensitive to noxious stimuli (the N cell). 2. Both forms of sensitization produced a central neuronal change, measured as an increase in the number of stimulus-evoked action potentials in cell 3 (an excitor of dorsal longitudinal muscles). 3. Intracellular stimulation of serotonin-containing neurons 21 and 61 mimicked the sensitizing stimuli, but stimulation of the Retzius cell, which also contains serotonin, did not. 4. Stimulation of the Leydig cell, which releases octopamine, decreased the strength of local bending.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

In Hirudo medicinalis, repeated stimulation of the pressure-sensitive P cell or the noxious-sensitive N cell sensitized the local bending reflex, increasing stimulus-evoked firing in cell 3; serotonin-containing neurons 21 and 61 mimicked this sensitization, while octopamine-releasing Leydig cells reduced bending strength.

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