Brain Lys-aminopeptidase activity. Changes during cycle and pregnancy

Department of Physiology, Medical School, University of the Basque Country, Bilbao, Spain.

Lys-aminopeptidase activity levels during the estrous cycle (estrous and proestrous, in the morning and afternoon) and the pregnancy (2nd, 7th, 14th and 20th day postinsemination and the parturition day), in several areas of the rat brain, were studied in this research. The selected brain regions were the frontal, parietal and occipital cortices, olphactory bulbus, thalamus, hypothalamus, hippocampus, amygdala, striatum and pituitary gland. The most significant changes were shown in the hypothalamus and the pituitary gland. Thus, in these areas, the higher cyclic enzyme levels were found in the proestrous stage. During pregnancy, there was a rise on the 7th and 14th days, with a decrease on the 20th day. Also, similar changes in the occipital cortex, striatum, hippocampus and amygdala were appreciated, but fewer than those observed in the hypothalamus and the pituitary. In conclusion, the activity of the aminopeptidase under study fluctuates during the estrous cycle and during pregnancy, as well as in the hypothalamic-pituitary axis and also in several extrahypothalamic areas of the rat brain.