1Neuroscience Research Institute, Peking University, Beijing 100083, China 
2Department of Clinical Medicine, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China 
3Department of Neurobiology, School of Basic Medical Sciences, Peking University, Beijing 100083, China 
4Key Laboratory for Neuroscience, Ministry of Education/National Health and Family Planning Commission, Peking University, Beijing 100083, China 
5Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China

Abstract 

Cognition and pain share common neural substrates and interact reciprocally: chronic pain compromises cognitive performance, whereas cognitive processes modulate pain perception. In the present study, we established a non-drug-dependent rat model of context-based analgesia, where two different contexts (dark and bright) were matched with a high (52°C) or low (48°C) temperature in the hot-plate test during training. Before and after training, we set the temperature to the high level in both contexts. Rats showed longer paw licking latencies in trials with the context originally matched to a low temperature than those to a high temperature, indicating successful establishment of a context-based analgesic effect in rats. This effect was blocked by intraperitoneal injection of naloxone (an opioid receptor antagonist) before the probe. The context-based analgesic effect also disappeared after optogenetic activation or inhibition of the bilateral infralimbic or prelimbic sub-region of the prefrontal cortex. In brief, we established a context-based, non-drug dependent, placebo-like analgesia model in the rat. This model provides a new and useful tool for investigating the cognitive modulation of pain.

Keywords

Context-based analgesia; Placebo analgesia; Pain; Hot-plate test; Cognition modulation; Opioid system; Prefrontal cortex

[SpringerLink]