Effects of differential environments on brain weights and enzyme activities in gerbils, rats, and mice

In 2 experiments, littermate male gerbils were kept in enriched (EC), standard colony (SC), or impoverished (IC) environments from 30 to 60 days of age. Cerebral effects of these environmental treatments were compared with results obtained previously with laboratory rats and mice. The EC gerbils show, in comparsion with IC, an increase in cortical weight and an increase in the cortical/subcortical weight ratio, a decrease in cortical acetylcholinesterase per unit of weight, and a slight increase in the ratio of cholinesterase to acetylcholinesterase in the cortex. These changes for the most part follow the pattern of EC‐IC effects found in the rat and mouse. In both absolute brain measures and in EC‐IC effects, the gerbil resembles the rat more closely than the mouse. The results extend the generality of findings within Rodentia from the family Muridae , which includes rats and mice, to the family Cricetidae , to which gerbils belong. Furthermore, the gerbil, unlike the laboratory rat and mouse, has not been subjected to many years of selection for laboratory conditions.