Pain influences food preference and food-related memory by activating the basolateral amygdala in rats.

Abstract

The amygdala has been demonstrated to contribute to pain-related behavior and food preference. Here, the effect of pain on food preference and food-matched visual-cue memory, in the presence or absence of a basolateral amygdala (BLA) lesion, has been evaluated using a novel innovative apparatus and protocol. Forty adult male Wistar rats wererandomly divided intofive groups (n = 8) as follows: control, pain, ibuprofen + pain, BLA lesion, BLA lesion + pain groups. Bilateral lesions of the BLA were produced by passing a current of 1.5mA for 7s. Pain was induced ontheright hind pawof theratsby sub-plantar injection of 50μl of 2.5% formalin. The animals were encountered with four different meals including wholemeal, wholemeal + sugar, white flour, and biscuit. Each test sessionconsisted of six trials with inter-trial intervals of 15min. The number of visits to each meal zone and port, the amount oftime spentin each food zone and port, traveled distance in each food zone, food consumption per each visit and the total food consumption were recorded. The control group showed a high biscuit preference and low white flour preference. Rats suffering BLA lesion and rats in the BLA lesion + pain group exhibited a shifted preference curve. They had a bias toward eating wholemeal + sugar rather than white flour and biscuit. This group also showed an impaired spatial memory. In conclusion, our findings suggest that the BLA may be involved in pain-induced food preference and food-matched visual-cue memory.