Reduced immunoreactivities of a vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide receptor (VPAC1 receptor) in the cerebral cortex, hippocampal region, and amygdala of aged rats

In this study, we examined expressional changes of VPAC1 receptor in aged rat brains using an immunohistochemical approach and found that its immunoreactivities are significantly reduced in the cerebral cortex, hippocampal region, and amygdala of aged rats. These results suggest that this reduction could underlie aging-associated memory/learning deficits and several other age-induced functional changes in these areas. However, the functional consequences of these down-regulations require further elucidation.