Pattern of acetylcholinesterase activity in the hypothalamus of the cobra, Naja naja.

Application of acetylcholinesterase (AChE) method to the hypothalamus of the cobra Naja naja revealed a clearly discernible pattern of activity in the nuclear groups. The magnocellular neurons distributed in various subdivisions showed strong reaction. Among the parvocellular groups, intense enzyme activity was observed in the cells of nucleus subfornicalis, nucleus hypothalamicus medialis, dorsal and ventral subdivisions of the nucleus hypothalamicus lateralis and the nucleus mamillaris. The paraventricular organ displayed strong amorphous activity accompanied by the intense reaction in the nucleus of the paraventricular organ. The neurons of the lateral preoptic area, nucleus periventricularis posterior, nucleus hypothalamicus dorsomedialis, nucleus lateralis recessus infundibuli and nucleus medialis recessus infundibuli showed heterogenous population revealing varying degrees of staining intensity. The perikarya of the nucleus suprachiasmaticus, nucleus hypothalamicus ventromedialis and nucleus arcuatus showed light staining. The rest of the nuclear groups were unstained. Whereas, lateral forebrain bundles and supraoptic decussation showed some AChE activity in the fibers, anterior commissure and optic chiasma were distinctly negative. The AChE-positive neuropil was confined to the lateral preoptic, and circumscribed periventricular tuberal areas. In the median eminence, a layer of fine AChE-reactive granules restricted to the subependymal zone was found; the ependymal layer was equipped with large, intensely positive somata.