Age-dependent changes in the β-endorphin content of discrete rat brain nuclei

Concentrations of β-endorphin were measured by radioimmunoassay in discrete brain nuclei of young (3 months) and old (24 months) rats. The β-endorphin content of all major structures known to contain this peptide with the exception of the eminence, is reduced (50.3 ± 2.8% of control) in old rats.