Decreased plasticity of glucoregulatory responses in aged rats: effects of chronic stress

These experiments were conducted to determine the effects of age and chronic stress on the ability of rats to attenuate stimulus-induced glucose and insulin responses during repeated exposure to a mild stressor. Young (5-month) and old (21-month) Fischer 344 male rats were either exposed to intermittent sessions of an escapable footshock stress for 3 months, or to no chronic stress. Afterwards, blood samples were obtained from each rat before, during, and after the first and fourth exposure to a novel motion stimulus. Between the first and the fourth exposure to the motion stimulus a pronounced attenuation of glucose and insulin responses was seen in both groups of young rats, and in old chronically stressed rats, but not in old control animals. Thus, it appears that the adverse effects of aging on plasticity of glucoregulatory response processes were significantly diminished by exposure of the animals to periodic challenges from their external environment.