[Pineal gland and brain structures monoamine oxidase activity in rats of different age]

Total monoamine oxidase activity was investigated in the pineal gland (epiphysis) and in three brain structures with the use of spectrophotometric method based on kynuramine oxidative deamination, the product (4-hydroxyquinoline) formation being detected at 327 nm. Female Wistar rats used for the experiment were 1.5-2, 4-5 and over 12 months old. In the pineal gland, olfactory tubercle cortex and median eminence (with surrounding tissue) the lowest activities (nmol/min per mg of the protein, M +/- m) were found in the group of rats aged 4-5 months (1.20 +/- 0.11; 0.62 +/- 0.05 and 4.36 +/- 0.25, respectively), whereas in the medial preoptic area the lowest activity was found in rats aged 1.5-2 months (1.55 +/- 0.11). In all of the four structures the highest activities were found in the group of rats aged over 12 months (2.17 +/- 0.40; 0.8 +/- 0.04; 6.61 +/- 0.56 and 2,01 +/- 0.15, respectively). The data obtained agree with the hypothesis that low monoamine concentrations in some brain areas (including some hypothalamic structures) of aged rats, are due to, at least partly, an increase in monoamine oxidase activity.