Senescent change in tissue weight and immunoreactive beta-endorphin, enkephalin, and vasopressin in eight regions of C57BL/6J mouse brain and pituitary

Tissue weights and immunoreactive (IR) content and concentration of beta-endorphin, enkephalin, and vasopressin were assayed for senescent change in anterior pituitary, neurointermediate pituitary, hypothalamus, hippocampus, striatum, dorsolateral cortex, and pons-medulla, as well as residual brain samples remaining after the other dissections. Groups of naive male C57BL/6J mice, 8-12 months old and 28-32 months old, served as subjects. Old mice exhibited significant decline in anterior pituitary and hippocampus weight. Significant increases with age were found in pons-medulla weight. IR beta-endorphin content decreased in hypothalamus and neurointermediate pituitary. IR enkephalin decreased in striatum and dorsolateral cortex. IR vasopressin content increased in hypothalamus and residual brain. Assays were replicated in later experiments using additional subjects, for total Ns of up to 54 mice. Although significant overall results were always consistent in direction from replication to replication, the magnitude of age change exhibited considerable variability. Such results suggest that single experiments on age changes in neuropeptides, particularly those giving negative results, should be carefully scrutinized and replicated before their acceptance as evidence for a transmitter's stability or instability throughout the lifespan.