Figure 1

UTP induced hyperalgesia and enhanced the excitability of small-diameter TG neurons in control rats. (A) Changes in rat facial mechanical pain threshold after injection of UTP or saline. UTP (100 nM, 50 μl) significantly decreased the mechanical pain threshold of the whisker pad 20 min after injection and remained for at least 3 h, which then declined 9 h after injection. n = 8 for each group, **, p < 0.01 vs saline. (B) Original traces of action potentials during intracellular current injection in control TG neurons. (C) Mean threshold currents (left panel) and mean number of spikes (right panel) in the presence, absence of UTP (30,100 μM) treatment and UTP (30 μM) co-application with suramin (100 μM) for 16 h. The depolarizing step current amplitude is twice as much as threshold. n = 8 neurons, *, p < 0.05, **, p < 0.01 vs control; #, p < 0.05, ##, p < 0.01 vs UTP30.