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

Position, shape and cytoarchitecture of the paraventricular nucleus were observed in 30 guinea pigs of both sexes, in serial frontal sections of the hypothalamus stained selectively for neurosecretion content, considering 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: medial, lateral, ventral and dorsal) as the basis for cytomorphological analysis. Morphology of PVN neurocytes was evaluated in 12 guinea pigs with regard to nine selected parameters. The results were formulated statistically. Cytomorphological comparisons were done between respective PVN units and subunits, depending on the side of sections in males. The results referring to the principal part of the right PVN in males and females were compared. Heterogeneity of the PVN-forming-cellular populations was revealed. Cytomorphological differences were noted between PVN and SON.