Figure 9. Spontaneous activity (SA) of IB4⁻ Aδ type neurons and its hypersensitivity to mechanical stimulation as well as behavioral mechanical hypersensitivity in CRP rats are I_h dependent.

(a) ZD7288 blocked both SA and mechanical hypersensitivity of IB4⁻ Aδ type neurons from CRP group, without obvious influence of resting membrane potential (n = 3 neurons from 3 rats). Action potential was evoked after tests to determine whether the generation of action potential was compromised. (b,c) Time course of behavioral mechanical hypersensitivity (b) and thermal hyperalgesia (c) from CRP rats before (pre) and after i.t. injection of 3, 10, 30 μg ZD7288 or saline. Note that mechanical hypersensitivity was alleviated by ZD7288 dose-dependently, while thermal hyperalgesia was unaffected (n = 9–10 rats for each group). (d) Spontaneous pain from CRP rats was largely attenuated by ZD7288 as well (n = 9–10 rats for each group). All data are expressed as mean ± S.E.M. *P < 0.05 as compared to control group.