Animal treatment
All animal procedures and study protocols were double-blind and carried out in strict accordance with the recommendations of the Guide for the Institutional Animal Care and Use Committee of Zhejiang University Medical Center. Mice were housed in cages at a controlled temperature (22 ± 0.1 °C) and humidity (50 ± 10%) with a 12-h light/dark cycle and provided with free access to food and water. All surgeries were performed under chloral hydrate anaesthesia, and all efforts were made to minimize animal suffering. All mice were killed by CO2 asphyxiation. Animals were randomised for treatment.
Specific pathogen‐free ICR mice (22-25 g), aged 4 weeks (male, 8; female, 8), were purchased from the Experimental Animal Center of the Zhejiang Academy of Medical Sciences [SCXK (Zhe) 2014-0001]. Nude mice (5 weeks old, male) were obtained from Beijing Vital River Laboratory Animal Technology Company (Beijing, China; SCXK [Jing] 2012‐0001) and maintained under specific pathogen-free (SPF) conditions. After adaptive feeding for one week, the nude mice were subcutaneously injected with HT29 cells into the rear flanks (1 × 107 cells/side). Nude mice with tumours of average volume = 50-60 mm3 were selected for the experiments.
To evaluate the neuroprotective effects of L-THP, mice with one-week adaptive feeding, were randomly allocated into 6 groups with 16 mice each (half male and half female): vehicle group, OXA-alone group, OXA and L-THP co-treatment groups, and L-THP-alone group. OXA was intravenously injected (iv, 8 mg/kg) twice a week for a total of four weeks (days 1, 4, 8, 11, 15, 18, 22, and 25). For the co-treatment groups, the mice were iv injected with 5% glucose solution containing L-THP (5-20 mg/kg) and OXA (8 mg/kg). Mice in the vehicle or L-THP-alone groups received equal volumes of 5% glucose without or with L-THP (10 mg/kg), respectively. The mouse behaviour and body weight were monitored and recorded after every administration. Twenty-four hours after the final administration, the animals were sacrificed and the DRGs were collected for analysis.
For evaluation of the antitumour activity, the tumour-bearing nude mice were allocated into 4 groups to evaluate whether L-THP co-treatment (10 and 20 mg/kg) would impair the antitumour efficacy of OXA (8 mg/kg): vehicle group, OXA-alone group, and OXA and L-THP co-treatment groups. Drugs were administered intravenously every two days for two weeks (days 1, 3, 5, 7, 9, 11, and 13), and the body weight and tumour size were monitored. Twenty-four hours after the final administration, the animals were sacrificed, and the tumours were collected, weighted, and stored for analysis. The tumour sizes were calculated according to the following formula: tumour size =a*b2/2 , where a is the long side of the tumour and b is the short side of the tumour.