Current Therapeutic Research

A Simple Contact Heat Experimental Pain Model for Evaluation of Analgesic Agents in Healthy Volunteers

2011-12-01

Abstract: Background: Human experimental pain models help to understand the mechanism of the underlying clinical pain conditions and can be adopted to test analgesic efficacy of drugs used in the management of pain. In early phases, the clinical development of new analgesic agents is severely hindered due to lack of reliable sensitive tests for the experimental pain models. Objective: The aim of the present study was to standardize and validate a simple contact heat pain model that can be used for future screening of various analgesic agents. Methods: The method was standardized by recording heat detection and heat pain detection threshold in degrees centigrade in 24 healthy volunteers. Reproducibility of the test procedure was evaluated by recording the thermal threshold parameters by a single observer on 2 sessions (inter-day reproducibility) and a second observer on 1 session (inter-observer reproducibility) separately. Validity of model was further tested by evaluating the analgesic effect of tramadol on 12 healthy volunteers. Results: Thermal pain model using contact heat method was found to produce low variability with coefficient of variation <5%. Inter-observer and inter-day reproducibility was very good, as shown by Bland–Altman Plot; with most of the values within 2 SD. There was a significant difference in both heat detection threshold and heat pain detection threshold produced by tramadol, as compared with placebo (P < 0.05). Conclusions: The newly developed pain model produces a type of experimental pain that is responsive to analgesic effects of tramadol at clinically relevant doses. The model might be useful in early screening of new therapeutic agents before proceeding to expensive clinical trials in acute and chronic pain sufferers.

Hemodynamic Effects of Epinephrine in Healthy and Hemorrhagic Shock Rats

Jing Wu, Dong-sheng Zhang, Mu-huo Ji, Zhuan Zhang, Jian-jun Yang — 2011-12-01

Abstract: Objective: The aim of this study was to investigate the hemodynamic effects of epinephrine intravenous injection in healthy and hemorrhagic shock rats. Methods: Forty Sprague-Dawley male rats weighing 250 to 300 g were randomly assigned to 4 groups: group NE, healthy rats receiving epinephrine 2 μg/kg; group NS, healthy rats receiving normal saline; group SE, hemorrhagic shock rats receiving epinephrine 2 μg/kg; and group SS, hemorrhagic shock rats receiving normal saline. Mean arterial blood pressure (MAP) and heart rate (HR) were recorded at the following time points: 0 seconds (baseline), 5 seconds, 15 seconds, 30 seconds, 1 minute, 2 minutes, 4 minutes, 6 minutes, 8 minutes, and 10 minutes (T0–9) after intravenous injection. Results: There were no significant differences in MAP and HR at baseline between groups NS and NE or between groups SS and SE. Compared with the figures for baseline, MAP had no significant change at all time points in groups NS and SS. MAP increased at T1–9 in group SE (P < 0.01). MAP increased at T1–3 and decreased at T5–6 in group NE (P < 0.01). There was no significant change in HR in all groups after epinephrine or normal saline injection. Conclusion: Epinephrine 2 μg/kg intravenous injection elicited biphasic changes in blood pressure, which included an initial increase and a subsequent decrease in healthy rats and induced a remarkable increase in blood pressure in hemorrhagic shock rats.

Glycyrrhizin and Long-Term Histopathologic Changes in a Murine Model of Asthma

2011-12-01

Abstract: Background: Licorice root has been widely used to treat bronchial asthma for many years. However, the effect of this herb on lung histopathologic features is not fully understood. Objective: In this study, we aimed to determine the effects of oral administration of glycyrrhizin, an active constituent of licorice root, on lung histopathologic features in BALB/c mice, in which the model of chronic asthma was established. Methods: Twenty-eight BALB/c mice were divided into 4 groups: control, placebo, dexamethasone, and glycyrrhizin. Mice in the treatment and placebo groups were sensitized with 2 intraperitoneal injections of ovalbumin and then were exposed to aerosolized ovalbumin for 30 minutes per day on 3 days each week for 8 weeks beginning on the 21st study day. In the last week of inhalational exposure, mice in the placebo group received saline and those in the treatment groups received either dexamethasone, 1 mg/kg, or glycyrrhizin, 10 mg/kg, via orogastric gavage for 7 consecutive days. Animals were humanely killed 24 hours after the last ovalbumin and drug exposure. Lung histopathologic findings were evaluated using light and electron microscopy. Results: As evaluated in the control, placebo, dexamethasone, and glycyrrhizin groups, respectively, the mean (SD) basement membrane thickness was 306.34 (36.91), 657.52 (98.99), 405.13 (96.1), and 465.01 (121.48) nm; subepithelial smooth muscle thickness was 7.22 (1.37), 11.24 (1.85), 5.62 (1.15), and 7.76 (1.11) μm; epithelium thickness was 19.48 (1.22), 41.62 (5.49), 22.59 (3.18), and 25.54 (4.68) μm; number of mast cells was 1.34 (0.19), 3.62 (0.5), 2.06 (0.77), and 2.77 (0.23)/16,400 μm2; and number of goblet cells was 0.32 (0.1), 4.92 (0.82), 0.66 (0.06), and 0.98 (0.15)/100 μm. Evaluation of lung histopathologic features demonstrated that the chronic asthma model of mice was successfully established, with significantly higher numbers of goblet and mast cells and increased thickness of epithelium, basement membrane, and subepithelial smooth muscle layers (P < 0.001 for all) in the asthma group compared with in the control group. The number of goblet (P < 0.001) and mast (P < 0.02) cells and the thickness of basement membrane (P < 0.001), subepithelial smooth muscle layers (P ≤ 0.001), and epithelium of the lung (P < 0.001) were found to be significantly lower in the glycyrrhizin group compared with in the placebo group. When the glycyrrhizin and dexamethasone groups were compared, there was no statistically significant difference between the 2 groups in the histopathologic parameters, including thickness of basement membrane (P = 0.514), subepithelial smooth muscle (P = 0.054), and epithelium (P = 1.0) and number of mast (P = 0.075) and goblet (P = 0.988) cells. Conclusions: The results of this study suggest that the group receiving glycyrrhizin had amelioration of all established chronic histopathologic changes of lung in the mouse model of asthma. Further studies are needed to evaluate the efficacy of glycyrrhizin in the management of asthma.

In Vivo Effects of Immunomodulators in a Murine Model of Fluorouracil-Induced Mucositis

David Tung, Peter H. Cheung, Gregory Tudor, Catherine Booth, Saurabh Saha — 2011-12-01

Abstract: Background: Fluorouracil (5-FU) is a pyrimidine analogue used as a cancer treatment. Its toxic side effects, including mucositis, are reported to occur in 40% of the treated patients. Because of the inflammatory component of mucositis, we explored the possibility of modulating this condition with an immunomodulatory agent and a tumor necrosis factor-α inhibitor. Objective: The aim of this study was to evaluate the effect of 2 immunosuppressive agents, etanercept and cyclosporine, in a murine model of 5-FU–induced mucositis. Methods: To study the short-term effects of 5-FU on mucositis, cyclosporine and etanercept were administered to mice after an injection of 5-FU. The animals (n = 8) were euthanized at 6 hours post-challenge. Hematoxylin and eosin–stained histologic sections of the small intestine were examined for signs of apoptosis. To further examine the potential of cyclosporine in the treatment of 5-FU–induced mucositis in a longer duration, the animals (N = 15) were given 2 challenges of 5-FU within 6 hours. All mice were dosed daily until day 9 with either cyclosporine (100 mg/kg) or phosphate-buffered saline (PBS). Results: Six hours after 5-FU challenge, 25 mg/kg etanercept and 50 mg/kg cyclosporine had no effect on 5-FU–induced apoptosis (P > 0.05). However, 100 mg/kg cyclosporine significantly reduced the cumulative level of apoptosis >41.6% of the intestinal crypt surface (P < 0.05). During long-term observation, all mice began to lose weight at a rate of approximately 0.8 g/day after 5-FU exposure. The rates of weight loss and survival were not affected by cyclosporine treatment. The diarrhea onset began on day 4 with 46.7% of the PBS-treated mice showing signs of diarrhea compared with 53.3% in the cyclosporine group. The diarrhea score for both groups plateaued on day 7, with a cumulative score of 41 for the PBS group and 50 for the cyclosporine group. Cyclosporine treatment did not affect the diarrhea onset day or severity compared with the PBS-treated group (P > 0.05). Conclusions: Our data indicated that etanercept is not a suitable treatment for 5-FU–induced mucositis. Despite decreased apoptosis in the gut, cyclosporine did not affect the severity of the diarrhea or survival. Therefore, we concluded that cyclosporine treatment was only effective in mediating the short-term apoptotic events in the intestines but has no long-term effect on the animals' survival and diarrhea.

Author Index

2011-12-01

Subject Index

2011-12-01