Cytoarchitectonic pattern of the hypothalamus in the catfish, Clarias batrachus (Linn.)

The hypothalamus of the catfish, Clarias batrachus has been investigated to reveal the organization of various parvocellular (aldehyde fuchsin-negative) nuclear complexes and to suggest homologies. The hypothalamus of C. batrachus can be divided into the preoptic area, postoptic area, tuberal area and the laterally placed inferior lobes. Application of cytoarchitectonic criteria permits the delineation of 9 distinct nuclear complexes in the preoptic area extending along the periventricular margin of the preoptic recess. The postoptic area is represented by only two nuclear groups, the nucleus postopticus lateralis and the nucleus of the horizontal commissure. The tuberal area consists of as many as 14 nuclei, some are divisible into subnuclei, arranged in an elaborate pattern. The nucleus lateralis tuberis is located in the mid-ventral margin of the tuberal area and revealed two subdivisions, the pars anterior and pars posterior. At the mid-tuberal level, the nucleus anterior tuberis is well-developed and revealed dorsal, ventral and lateral subdivisions. The paraventricular organ is encircled by nucleus of the paraventricular organ. The conspicuous lateral recesses are flanked dorsally by nucleus recessus lateralis superior and ventrally by nucleus recessus lateral by nucleus recessus lateralis superior and ventrally by nucleus recessus lateralis inferior. In the caudal tuberal area, in close proximity of the pituitary, the nucleus arcuatus hypothalamicus is described for the first time. The recessus posterioris is encircled by nucleus recessus posterioris. The inferior lobes are massive and each consists of 7 well-defined nuclear complexes. The nucleus lobi inferioris centralis is represented by giant-sized cells clustered in the center of the lobes. The periventricular nucleus of the inferior lobes occupies the area surrounding the recesses of the inferior lobes. The hypothalamus shows 4 circumventricular organs. The organum vasculosum laminae terminalis is situated along the ventral wall of the preoptic recess. While the paraventricular organ is located in the dorsal wall of the third ventricle, the posterior recess organ is located in the postero-ventral wall of the third ventricle. The saccus vasculosus is small, capsule-like and located caudally in between the two mamillary nuclei.