Atlas of the rat brain: quantitative distribution of the choline acetyltransferase.

We have developed a fluorescence microphotometry system for microanalysis of the quantitative distribution of neurotransmitters and their related chemical substances in the brain slice. In the present study, the extensive distributions of cholinergic systems were analyzed quantitatively and in detail throughout the rat whole brains by this novel method through immunohistochemical staining of choline acetyltransferase (CAT). The rat whole brain was slice coronally and continuously, and 50 slices were chosen at approximately 500 microns intervals and stained immunohistochemically for CAT. Immunohistochemical fluorescence intensities were measured through a 6 microns phi (on the slice) pinhole of a microscope, the brain slice was moved along the X- or Y-axes stepwise at 40 microns intervals under the objective lens of the microscope, and the distributions of fluorescence intensities were analyzed over the entire surface of the slice. The brain was divided into approximately 5,000,000 areas, and immunohistochemical fluorescence intensities of those areas were quantitatively measured. The obtained fluorescence intensities of CAT were classified into 8 ranks and were indicated by color coding and by three-dimensional graphics. Also, the actual fluorescence intensity values in large brain regions were presented. This type of brain atlas of the neurotransmitter or its related chemical substances provides very important information on their dynamics in the brain under experimental as well as pathological conditions. Also, this quantitative and detailed analysis is useful for combining morphological data with those from neurochemical and behavioral analyses of brain function.