Stress Differently Affects Meal Pattern in Selectively Bred Rats

Abstract

Stress dramatically alters many behaviors, such as meal patterning. In rats, stress usually reduces overall food consumption and body weight. Rats exposed to a severe stressor eat meals less frequently, but these meals are slightly larger and are eaten more quickly (Dess & Vanderweele, 1993). Rather than seeing this reduction in food consumption as a nonsensical reaction, it can be seen as a regulatory shift, in which the rats attempt to satisfy their energy requirements while incurring the least cost. By eating fewer but larger meals, the rats may place themselves at less risk. The Occidental College High-Saccharin (HiS) and Low-Saccharin (LoS) rats differ in emotionality and stress vulnerability in addition to the difference in the saccharin ingestion phenotype (Dess, 1991). Rats were exposed to moderate stress to see if the groups would react differently to stress in their eating patterns. The stressor stimulated differential changes between the lines on the second day for average intermeal interval: HiS rats ate more frequently, while LoS waited longer between meals, acting more like they had been exposed to a severe stressor. In the dark period ? when nocturnal animals such as rats are more active -- stress lowered total intake for both lines, but affected meal size differently in the two lines, increasing meal size in the LoS and decreasing it in the HiS. These findings suggest that animals high and low in emotionality adjust their eating strategies differently in the face of stress.