Fig. 2.

Semi-intact preparations used in this study. A: the ventral nerve cord from segments 1–7 was dissected and pinned onto a Sylgard dish but remained attached to the intact portion of the preparation (segments 8–10), which was loosely pinned to permit shortening. Electromyogram (EMG) electrodes were inserted under the skin to record the shortening response. Dashed line represents a Sylgard ring placed around the intact portion of the preparation to ensure that drugs were exclusively applied to the CNS portion of the preparation. Petroleum jelly was used to secure the ring to the bottom of the dish. In segment 3, intracellular electrodes were used to impale the nociceptive neuron (N) to deliver HFS to induce sensitization and to record synaptic transmission between the P cell and L motor neuron (L). B: for experiments in which sensitization was elicited with noxious cutaneous stimulation, the semi-intact preparation setup was the same with the following changes: The CNS portion of the preparation included ganglia from segments 1–5, and the intact portion of the preparation consisted of segments 6–11 to accommodate both EMG recording electrodes and a second pair of Teflon-coated silver wire electrodes to deliver sensitizing stimuli in segments 6 and 7. Inset at top: drawing of an intact leech, with dashed box representing the portion of the animal used in the semi-intact preparation.