Asymmetric intra and inter-hemispheric subcellular rat brain correlation of arginyl-aminopeptidase activity during development and aging

The functional significance of brain asymmetry is still largely unknown. Studying the level of correlation of neuropeptide-degrading activities between subcellular fractions such as synaptosomal, of the left and right hemispheres of male rats during development and aging could provide relevant data on their functional role during these periods. The present study analyzes the level of correlation of a enkephalin- or angiotensin III-degrading activity, such as membrane-bound arginyl-aminopeptidase activity (M-B ArgAP) between the left versus right homogenate and/or synaptosomal subcellular fractions obtained and processed independently from both brain hemispheres during development and aging. The tested ages were: fetuses, rats of one week, one month, five month and two year old. In homogenate, the results demonstrate high levels of positive correlations (left versus right homogenate) with high levels of significance, without differences among the ages analyzed. In synaptosomes the results demonstrate positive correlations with a level close to statistical significance (left versus right synaptosomes) in fetuses, significant correlations at one week, one month and five months, particularly at one week and five months, and a radical decrease in the level of left versus right correlation between synaptosomes of two-year-old animals, which could suggest a functional loss of the bilateral synaptic interaction that could be carried out at earlier ages by M-B ArgAP activity. The interaction between left or right synaptosomes versus left or right homogenates demonstrate decreasing levels of positive correlation from fetuses to five month old rats, without differences between correlations of the left synaptosomes with correlations of the right ones. However, in two year old rats the values of correlations of the left synaptosomes diverged significantly from the right ones. While left synaptosomal correlations exhibited positive values, the right correlations exhibited negative ones, showing. a clear asymmetry between both sides in aged rats suggesting a marked reduction with aging of the synaptic function in the right hemisphere.