Biomedical subjects
Publications and source records attributed to M Bixo.
A high molecular weight polypeptide (ca. 24000 Da) which contained only (Leu) enkephalin immunoreactivity, has been isolated from spinal cord. Molecular size and the presence of at least one copy of (Leu)enkephalin was established by chromatography in combination with a specific radioimmunoassay for (Leu)enkephalin.
Estradiol and progesterone both accumulate in the brain. Specific cytosol receptors are present in certain CNS regions. Estradiol increases but progesterone decreases the brain's excitability. The effects can be mediated via monoamine systems or a change in monoamine metabolizing enzymes, but other mechanisms are possible. The combination of estradiol and progesterone seem to provoke a negative mood change in certain sensitive women. Estradiol and progesterone singly seem not to have these negative effects on mood, but perhaps positive effects instead.
The uptake of progesterone in the intact female rat brain was studied in 25, immature, female rats which were given an injection of 4 IU PMSG on the 25th day of life. The rats were killed 53-55 h after their first ovulation. Amounts of progesterone were measured in seven brain areas, peripheral fat and muscle tissue and blood plasma. The analyses were done by radioimmunoassay after extraction with ethanol or diethylether. The highest mean concentration was found in the cerebral cortex, followed by the hypothalamus, the hippocampus, the striatum, the midbrain, the cerebellum and the medulla oblongata (mean +/- SE pg/mg 29 +/- 2.0, 27 +/- 5.2, 19 +/- 2.4, 15 +/- 1.8, 14 +/- 2.0, 12 +/- 1.7 and 11 +/- 1.9). The concentration of progesterone in the cerebral cortex was significantly higher than in all other areas except the hypothalamus (p less than 0.001). The cerebral cortex, the hypothalamus and the hippocampus had progesterone levels that were significantly higher than in peripheral fat tissue (p less than 0.01). The plasma progesterone level correlated positively with that in the cerebral cortex (r = 0.62, p less than 0.01). Some earlier studies have shown high accumulation in the hypothalamus, but low in the cerebral cortex. One reason for the different results might be the nonphysiological models used in the earlier studies.