A SEGMENTAL MAP OF ARCHITECTONIC SUBDIVISIONS IN THE DIENCEPHALON OF THE FROG RANA-PEREZI - ACETYLCHOLINESTERASE-HISTOCHEMICAL OBSERVATIONS

This work examines frog diencephalic subdivisions from a segmental vie wpoint and adds a number of details to the atlas of the bullfrog dienc ephalon reported by Neary and Northcutt [1983]. Acetylcholinesterase h istochemistry was performed on brains of Rana perezi, sectioned either sagittally or in a plane roughly parallel to the optic tract to optim ize detection of segmental landmarks. This material provided a very de tailed picture of individual neurons, neuropils and some fiber tracts expressing the enzyme in diverse patterns characteristic for each dien cephalic region. The main diencephalic areas previously recognized in the bullfrog appeared subdivided into smaller AChE-chemoarchitectonic units. Modified subdivisions are proposed for several entities: preopt ic, suprachiasmatic, entopeduncular, ventral thalamic, anterior thalam ic, pretectal, hypothalamic and tuberculum posterior regions. A number of cell groups are described for the first time in frogs. This mappin g is expected to be useful for the interpretation of immunocytochemica l and experimental hodologic results in the diencephalon of frogs and opens new possibilities for comparative analysis.