Fluctuations in neuronal activity and sexual dimorphism in the medial preoptic nucleus of the hypothalamus during postnatal development of the rat
Smollich, A.; Wenkel, R.
Journal für Hirnforschung 29(4): 357-366
1988
ISSN/ISBN: 0021-8359 PMID: 3183360 Document Number: 309580
The medial preoptic nucleus of the hypothalamus of the rat is characterized by a sexual dimorphism of one of its substructures, the "sexually dimorphic nucleus of the preoptic area (SDN-POA)" (Gorski et al. 1980), which becomes light microscopically visible at lower magnification. The SDN-POA, showing up as a concentration of perikarya, is principally larger in males than in females. Furthermore, the sexual dimorphism of the medial preoptic nucleus is reflected in temporary significant differences of the nuclear size of its neurons, which again are discussed as the correlate of differences of the neuronal activities. Karyovolumetrically verified variations of activities of the medial preoptic nucleus were observed during continuous studies at totally 180 rats (90 females and 90 males), aged between 5 (P 5) and 60 (P 60) days. These are already known in other cerebral structures and also typical for the comparably studied neurons of the granular layer. They are especially distinct during the first 3-4 days of the postnatal development and characterized by larger amplitudes in male than in female rats. Typical are peaks of activities at P 10 and P 20 as also--especially in males--at P 45. The variations of the neuronal activities are discussed as summarizing reflection of gene activities, correlated with cytological processes of development and differentiation, which again are superimposed by a total of age related and sex specific performances of the Nucleus-preopticus-medialis-neurons. The karyovolumetrically verified sexual dimorphism of the medial preoptic nucleus, appearing as a differently developed SDN-POA, is a reflection of the sex specific morphological-functional differentiation of the central nervous system. A more for-reaching, specifying discussion of the results, complicated by the functional complexity of the medial preoptic nucleus, will be obtained by directed experimental studies.