Morphological heterogeneity of neurosecretory magnocellular nuclei of the guinea pig hypothalamus. I. Microscopic pattern and cytomorphological analysis of the supraoptic nucleus.

Position, shape and cytoarchitecture of the supraoptic nucleus were observed in 30 guinea pigs of both sexes, in serial frontal sections of the hypothalamus stained selectively for neurosecretion content, with regard to the sex of the animals examined and hypothalamus sides. Three morphological units of the nucleus were distinguished (parts: oral, principal and caudal) and four subunits (zones: hypothalamic, optic, basal and central) as a starting point to work out a model of its cytomorphological heterogeneity. A detailed cytomorphological analysis was done within the distinguished morphological units and subunits of the supraoptic nucleus (SON) in 12 guinea pigs of both sexes. Using a light microscope equipped with a micrometric ocular, neurocyte morphology was evaluated on the basis of nine distinctive parameters. The results of the observation were formulated statistically. Cytomorphological comparisons were done between respective SON units and subunits, depending on the side of sections in males. The results referring to the principal part of the right SON in males and females were compared. Heterogeneity of the SON-forming-cellular populations was found.