|姜召彩; 罗非; 王锦琰|
Pain has sensory-discriminative and emotional-motivative components. Although the pathways of the sensory component of pain have been extensively investigated, the mechanisms underlying the affective component of pain need to be further explored. In recent years, conditioned place avoidance (CPA) paradigm has been used to investigate the affective component of pain. Animal and human studies have indicated prefrontal cortex is involved in the modulation of pain emotion. Thus, the present study investigated the role of prefrontal subdivisions, prelimbic cortex (PL) and infralimbic cortex (IL), in the acquisition and expression of formalin-induced CPA (F-CPA). Seventy-seven male Sprague-Dawley rats were included in our study. After recovery from cannula implantation surgery, rats underwent the F-CPA training, with hindpaw intraplantar injection of formalin (5%, 50 μl) in one conditioning chamber and no treatment in the other. GABAA receptor agonist muscimol (0.9% NaCl, 0.55 nmol/μL, 0.2 μL/side) was bilaterally infused into PL or IL before the formalin-paired training or test to explore the effect of PL or IL temporary inactivation on the acquisition and expression of F-CPA respectively. Formalin-induced licking behavior and locomotor distance after muscimol infusion were also measured. The results showed that inactivation of PL but not IL prevented acquisition and expression of F-CPA. Moreover, inactivation of neither of them had effect on formalin-induced nociceptive behavior or locomotor distance, suggesting the impaired learning of F-CPA was not due to reduced sensory pain perception or locomotor activity. These findings demonstrated the important role of PL rather than IL in the acquisition as well as expression of F-CPA.
|关键词||痛情绪 前边缘皮层 下边缘皮层 福尔马林建立的条件位置厌恶|