Figure 8.

Attenuation of mechanical allodynia of inflamed TMJ by blocking TRPV1 in the hippocampus of estradiol (200 μg)-treated ovariectomized rats. A, B, Head withdrawal threshold was partially reversed by intrahippocampal injection of TRPV1 antagonist capsazepine (A) and 5′-iodo-resiniferatoxin (B) into the CA1 region of the hippocampus. The baseline of head withdrawal threshold was not different between intrahippocampal injection of capsazepine (30 nmol, n = 6) and vehicle (n = 5) or 5′-iodo-resiniferatoxin (0.5 nmol, n = 5) and vehicle (n = 5) before induction of TMJ inflammation (p > 0.05). The threshold was dramatically decreased 20 h after induction of TMJ inflammation and was partially reversed by intrahippocampal injection of capsazepine (30 nmol, n = 6) and 5′-iodo-resiniferatoxin (0.5nmol, n = 5), but not vehicle (n = 5). *p < 0.05 versus vehicle group at the same time point (independent-samples t test). C, D, Food intake was improved by intrahippocampal injection of TRPV1 antagonist capsazepine (C) and 5′-iodo-resiniferatoxin (D) into the CA1 region of estradiol-treated ovariectomized rats. Food intake was not different between intrahippocampal injection of capsazepine (30 nmol, n = 6) and vehicle (n = 5) or 5′-iodo-resiniferatoxin (0.5 nmol, n = 5) and vehicle (n = 5) before induction of TMJ inflammation. Intrahippocampal injection of capsazepine (30 nmol, n = 6) or 5′-iodo-resiniferatoxin (0.5 nmol, n = 5), but not vehicle (n = 5), blocked the decrease of food intake caused by TMJ inflammation. *p < 0.05 versus vehicle group (independent-samples t test).