Figure 1

Increased anxiety-like behavior in the arthritis pain model (A) is decreased by a CRF1 receptor antagonist (B). Anxiety-like behavior of adult male rats was determined by measuring the open-arm preference (ratio of open arm entries to the total number of entries expressed as %) in the elevated plus maze (EPM) test. (A) Open-arm choice did not change in control rats (n = 5) after intraarticular saline injections on day 2 compared to normal baseline on day 1. Rats with arthritis (n = 7; 5–6 h postinjection of kaolin/carrageenan into the knee on day 2) showed a significantly decreased open-arm preference compared to normal baseline on day 1 (P < 0.05, paired t-test), suggesting increased anxiety-like behavior. (B) A CRF1 receptor antagonist (NBI27914) administered systemically (5 mg/kg i.p.; n = 5) or into the CeA by microdialysis (100 μM, concentration in microdialysis fiber, 2 μl/min; n = 5) increased the open-arm preference significantly (P < 0.05, compared to vehicle groups; Newman-Keuls Multiple Comparison Test). Systemic (i.p.) application of saline (n = 5) or intra-amygdalar administration of ACSF (n = 5) as vehicle controls had no significant effect on open-arm choices compared to arthritic rats without any interventions (n = 6; P > 0.05; Newman-Keuls Multiple Comparison Test). Bar histograms show the mean ± SEM. * P < 0.05.