THE EXCITATORY RESPONSE OF THE ADRENAL SYMPATHETIC-NERVE TO SEVERE HYPOXIA DECREASES IN AGED RATS

The age-related changes in the sensitivity of the adrenal sympathetic nerve to hypoxia were investigated in anesthetized young adult (3-4 mo nths old) and aged rats (25 26 months old). Hypoxia with end-tidal O2 concentration (F(ETO2)) at 6 2% caused excitation of adrenal nerve act ivity in the young adult and the aged rats. There was a significant de crease in the responses al 3 and 2% F(ETO2) in the aged rats compared to the young adult rats at either peripheral chemoreceptors-intact or -denervated condition. Reduced responsiveness of the central chemorece ptors to severe hypoxia is suggested as a possible factor in the age-r elated decreases.