ECE2021 Oral Communications Oral Communications 13: Pituitary and Neuroendocrinology (6 abstracts)
1Universidad Autónoma Metropolitana-Xochimilco, Sistemas Biológicos, Mexico D.F., Mexico; 2Cinvestav, Fisiología, Ciudad de México, Mexico
We determined in vitro activity of 17β-estradiol and or progesterone on glutamate conversion to GABA in different GABAergic regions from the brain of castrated and non-castrated rats. The glutamate decarboxylase catalyzes this conversion; there are two different isotypes of glutamate decarboxylase, GAD65 and GAD67. Whereas GAD65 is a membrane enzyme, GAD67 is present in the supernatant obtained after centrifuging to 14, 000 g. We treated three different groups of ovariectomized rats with increasing week-dose of 17β-estradiol, progesterone, and the combination of both for five weeks. We maintained one group of the ovariectomized rats as a control. After five weeks of treatment, we separated the rat-brain. We dissect the brain regions which have previously been related to the sleep process: mammillary bodies, locus coeruleus, substantia nigra, and the ascending reticular activating system. After homogenates and centrifuge these tissues, we incubating the membrane fraction and supernatant separately with tritiated-glutamate a pyridoxal phosphate. We assessed the decarboxylation of glutamate for the formation of a Schiff base, which was purified by thin-layer chromatography. We identified this Schiff base by its fluoresces at λ 302 nm. We quantify this conversion by counting the radioactivity present in the fluorescence zone. Results indicated that 17β-estradiol-treatment increased the GAD65 and GAD67 activity in all the studied brain-regions compared with those of the ovariectomized (vehicle-treated) control. In contrast, progesterone increased GAD65 and GAD67 activity only in the ascending reticular activating system and locus coeruleus. Furthermore, 17β-estradiol plus progesterone-treatment also increased GABA synthesis in the ascending reticular activating system and locus coeruleus compared to the vehicle-treated control. However, the ovariectomized (vehicle-treated) control showed only GAD65 and GAD67 activity in the mammillary bodies and substantia nigra. The brain GABAergic structures studied are involved in the process of sleep. Therefore the increase of the GABA formation induced by 17β-estradiol is responsible for maintaining sleeping in rats. However, the progesterone role seems to be a regulator of this process because the locus coeruleous and the ascending reticular activation system are responsible for inducing the sleep-wake rhythm.