Standardized Bioflavonoid Compositions as Analgesics 159 (Hamilton Company, Reno, Nevada, cat # 89520-0012) (Badilla, Mora, Lapa, & Emim, 1999; Dubuisson & Dennis, 1977; Kanegusuku et al., 2007; Tjolsen, Berge, Hunskaar, Rosland, & Hole, 1992; Zhang, Li, Zhang, Ding, & Du, 2007). Mice were immediately transferred to their individual observational chamber. The duration of time spent flinching and/or licking of the inflamed hind paw was monitored and recorded over a period of 60 min in a 10 min time block. Mirrors positioned behind the chambers enabled observation of the right hind paw when it was obscured from direct view. Visceral Pain Perception (Writhing Test) Mice (N = 12 per group) were habituated under an inverted Plexiglas observa- tion chamber for 30 min to allow them to acclimatize to their surroundings. An- imals were treated orally with 100 mg/kg of UP446, 100 mg/kg of ibuprofen, or vehicle control (propylene glycol) 30 min before intraperitoneal administration of freshly made acetic acid solution (0.7% in 0.9% NaCl) at 10 ml/kg using 26 gauge needle syringes. The experiment was carried out at room temperature. After the challenge, each animal was placed back into its own individual section of the obser- vation chamber and the number of constriction of the abdominal muscle together with stretching was counted cumulatively over a period of 30 min. Dose Selection A dose of 150 mg/kg for carrageenan-induced inflammation and 100 mg/kg for formalin and visceral pain perception tests were selected after a series of dose- response curve studies (data not shown) in respected models. UP446 performed better at the disclosed doses and was reproducible. RESULTS Carrageenan-Induced Hyperalgesia The intraplantar injection of carrageenan in rats led to time-dependent increase in paw volume that was maximal after 4 hr and remained elevated thereafter. As shown in Table 1, animals treated with an oral dose of 150 mg/kg UP446 showed 37.8%, 39.5%, 30.7%, and 33.3% reduction in pain sensitivity at 1 hr, 2 hr, 4 hr, and 6 hr, respectively, when compared to the vehicle control animals. These per- centage reductions were statistically significant at each time point analyzed against vehicle control (Table 1). The positive control ibuprofen showed statistically signif- icant 20.3%, 39.8%, 32.6%, and 45.1% reduction at 1 hr, 2 hr, 4 hr, and 6 hr time points, respectively, compared to vehicle control (Table 1). However, when UP446 and ibuprofen data were compared, no statistically significant difference in inhibi- tion was observed (P = .19 for 1 hr, P = .95 for 2 hr, P = .87 for 4 hr, and P = .22 for 6 hr). As seen in Figure 1, animals treated with UP446 showed up to 3.4, 1.6, 2.2, and 2.6-fold decreases in paw edema after 1 hr, 2 hr, 4 hr, and 6 hr of carrageenan injec- tion compared to vehicle control. Similarly, animals that were administered ibupro- fen showed 1.4, 1.3, 1.9, and 1.4-fold decrease in paw edema after 1 hr, 2 hr, 4 hr, and 6 hr of inocula compared to vehicle control (Figure 1). These fold reductions