Figure 2. The excitatory effect of ionophoretic administration of a selective 5-HT₃ receptor agonist (phenylbiguanide, PBG) is attenuated by the selective 5-HT₃ receptor antagonist granisetron.

A, the excitatory response of an NTS neurone to the ionophoretic administration of phenylbiguanide (PBG, 10 nA) during the bar is attenuated when given in the presence of ionophoretic administration of granisetron (20 nA). From the top, traces show a continuous rate histogram (spikes bin⁻¹) and the raw extracellular recording of neuronal activity (cell, μV). B, histograms of the mean data of NTS neuronal activity with vertical bars representing s.e.m. From left: baseline activity (CON), activity evoked by ionophoretic administration of PBG alone (5–120 nA; PBG), or in the presence of granisetron (5–60 nA; PBG + gran), and recovery of baseline activity (REC). *P < 0.05, n = 15.