• Zheng-Lan Han, Zi-Long Wang, Xu-Hui Li, Ning Li, Jia-Xin Pan, Ting Zheng, Quan Fang, and Rui Wang.
• From the Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, Gansu Province, China.
• Anesth. Analg. 2015 Nov 1; 121 (5): 1360-8.

BackgroundCannabinoids produce analgesia in several pain models, but the undesirable side effects from high doses of cannabinoid drugs limit their clinic use. Our recent results indicate that cannabinoid-induced antinociception was enhanced by neuropeptide VF (NPVF). Here, we investigate whether low-dose cannabinoid agonists combined with NPVF can produce effective antinociception with limited side effects.MethodsThe in vivo properties of (R)-(-1)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-napthalenylmethanone (WIN55,212-2) given alone and its combination with NPVF were evaluated in nociceptive modulation, locomotor activity, gastrointestinal transit, and tolerance development assays after intracerebroventricular administration in mice.ResultsIn the radiant tail-flick test, the antinociception of combination of WIN55,212-2 and NPVF was more potent than that of cannabinoid agonist given alone, with an ED50 shift from 3.51 to 0.69 nmol; 9 nmol WIN55,212-2 alone and 3 nmol WIN55,212-2 combined with NPVF induced equivalent antinociception after supraspinal administration. The cannabinoid-potentiating effects of NPVF were reduced by both the cannabinoid receptor type 1 and the neuropeptide FF receptor antagonists. In the formalin assay, WIN55,212-2 combined with NPVF also significantly reduced pain-related behaviors. However, the combination of WIN55,212-2 with NPVF exerted significant hypoactivity in a manner similar to high doses of WIN55,212-2. It was important to note that the combination of WIN55,212-2 with NPVF produced nontolerance-forming antinociception and weaker inhibition of gastrointestinal transit compared with high dose of WIN55,212-2.ConclusionsThese data suggest that the cannabinoid agonist combined with NPVF produces effective antinociception-lacking tolerance via both cannabinoid receptor type 1 and neuropeptide FF receptors in the brain.

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