Figure 3.
Effects of 5-HT2 receptor agonists on cells activated by myelinated fibres. (A) Single sweep showing the short latency of the spike evoked by vagal stimulation, as expected for fast conducting fibres (myelinated). (B1) Ratemeter record (1 s bins) showing that administration of phenylbiguanide (PBG, 10 μg kg−1, arrow) inhibited the firing of a Group 1 cell, (B2) peri-stimulus time histograms (PSTH, 1 ms bins, 40 sweeps) of the same cell showing that application of MK-212 (MK, 30 nA, right) reduced the number of evoked spikes compared to pre-drug (control, left). (C1) Ratemeter record (1 s bins) showing that administration of PBG (10 μg kg−1, arrow) did not affect the firing of this Group 3 cell, and (C2) PSTHs (1 ms bins, 40 sweeps) of the same cell showing that ionophoretic application of DOI (20 nA, right) had no effect compared to pre-drug (control, left). (Vertical bars at t=0 ms represent the stimulus artefacts and numbers in brackets are the number of evoked discharges counted). ABP: arterial blood pressure.