INTRODUCTION Early cancer diagnosis and various therapeutic options have extended the life expectancy of cancer patients. Unfortunately, however pain management for patients with malignant disease has not been effective, which decreased the quality of life of cancer patients. Approximately, 20-50% of all cancer patients suffer pain and 75-90% of terminal cancer patients experience severe pain [1]. The most difficult type of cancer pain is bone cancer pain, which occurs primarily in bone or secondarily by meta- stasis from distant organs to bones [2-4]. The character- istics of bone cancer pain are constant, increased with time and exacerbated after movement or weight-bearing on the affected limb [5-7]. The most commonly used an- algesics for cancer pain control are non-steroidal anti-in- flammatory drugs (NSAIDs) and opiates [8]. However, de- spite the widespread use of both drugs, their analgesic ef- fect is often limited and they sometimes cause side effects [9,10]. Therefore, the effective and safe analgesics for cancer pain management are needed. The root of Pannax ginseng C.A. Meyer, or ginseng, has been used as an herbal medicine [11]. Therefore, it has been used for a long time to relieve some types of pain such as toothaches, abdominal pain and neuralgia in tradi- tional folk medicine. The major active constituents of gin- seng are ginsenosides [12]. It has been reported that gin- senosides inhibited postoperative pain and inflammatory pain at the spinal level of rats [13-15]. Therefore, we hy- pothesized that spinal ginsenosides may reduce cancer pain. The aim of this study was to evaluate the efficacy of an intrathecal ginsenosides in a murine bone cancer pain model. MATERIALS AND METHODS All procedures were performed following the approval by the Institutional Animal Care and Use Committee of Chonnam National University. The experiments were done on adult male C3H/HeJ mice, weighing 20-25 g. These strains were selected for their histocompatibility with the NCTC 2472 tumor line [American Type Culture Collection (ATCC), Rockville, MD, USA]. The mice were housed in a vivarium, maintained at 22 ± 0.5oC with a 12-h light/dark cycle and were allowed to access food and water. MH Yoon, et al / Intrathecal and Bone Cancer Pain 231 Tumor cells were incubated and cultured in NCTC 135 medium (Sigma-Aldrich Co., St. Louis, MO, USA) with 10% horse serum (ATCC) at 37oC in a 5% CO2 in air atmosphere, and passed two to three times weekly. Tumor cells in- oculated into the femur of the mice under intraperitoneal ketamine (100 mg/kg) anesthesia according to a previously described method [16]. When the mice did not respond to a paw pinch, the right thigh of the mice was shaved and disinfected with povidone-iodine. A 1 cm skin incision was made along the lateral femur and a 25 gauge needle was inserted into the medullary cavity of the distal femur. Tumor cells were injected using a hand-driven, gear-op- erated injector connected to the 25-gauge needle with polyethylene-10 tube. Twenty μl of minimal essential me- dium (MEM) alone (sham; n = 3) or MEM containing 2.5 × 105 tumor cells (n = 6) were injected slowly. The in- jection site was sealed with dental amalgam, and the skin was closed with 6-0 silk sutures. Radiographics and the determination of the withdrawal threshold in tumor cells-injected femur were done at 7, 14, 21 days after tu- mor cells inoculation to assess the bone tumor and bone cancer pain development. Ginsenosides were used in this study and provided by the Korea Ginseng and Tobacco Research Institute (Daejon, Korea) and dissolved in dimethylsulfoxide (DMSO). Ginse- nosides were intrathecally administered according to the procedure of Hylden and Wilcox [17] using a 25 μl Hamilton syringe with a 30-gauge needle. The needle was inserted between L5 and L6 and the injection volume was 5 μl. The intrathecal placement of a needle was confirmed by ob- servation of a tail flick of the mice. The development of bone cancer pain was evaluated by measuring the mechanical sensitivity of the tumor cells-injected femur. The withdrawal threshold in response to mechanical stimulation was measured with von Frey fil- aments (Stoelting, Wood Dale, IL, USA). One of von Frey filaments (0.4-3.6 g) was applied to the tumor cells-in- jected femur for 4 s while the filament was bent. Sharp withdrawal or flinching of paw was regarded as a positive response. If no response was noted at a pressure of 3.6 g, mice were assigned to this cutoff value. The 50% paw withdrawal threshold was determined according to a pre- vious method of Dixon [18]. Fourteen days after tumor cells inoculation, the be- havioral study was commenced. The mice were placed in- dividually in plastic cages with a plastic mesh floor (4 ×