Age-related changes in monoamines within the olfactory bulbs of the Fischer 344 male rat

In this report the olfactory bulbs (OB) were removed from 5-6 month, 15-16 month and 25-26 month male Fischer 344 rats and assayed for concentrations of monoamines and their metabolites using HPLC-EC. Concentrations of norepinephrine were significantly greater in 25-26 and 15-16 compared to the 5-6 month old rats. By contrast, the norepinephrine metabolite, 3-methoxy-4-hydroxyphenyl glycol (MHPG), was significantly lower in the 25-26 vs. the 15-16 and 5-6 month old animals. While OB concentrations of dopamine and serotonin did not differ among the three age groups, their respective metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly reduced in the 15-16 and 25-26 month old animals compared to the 5-6 month old animals. These data show some of the age related changes which occur in the monoamines of the OB of the Fischer 344 rat. The salient bi-directional changes which are observed between norepinephrine and its metabolite, MHPG, are particularly intriguing since they reveal some of the mechanistic alterations that occur in the OB noradrenergic system, which may underlie the age related changes in olfactory related memory/recognition processes.