DISTRIBUTION OF CHOLINE-ACETYLTRANSFERASE IMMUNOREACTIVITY IN THE BRAIN OF THE LIZARD GALLOTIA-GALLOTI

The aim of the present study is to provide a complete description of t he distribution of choline acetyltransferase (ChAT) immunoreactivity ( i) in the brain of the lizard Gallotia galloti, on the basis of two di fferent primary antisera: rat anti-ChAT and rabbit anti-chicken ChAT. Considering that the brain is a segmented structure, we have analysed our data with respect to transverse segmental domains (or neuromeres), which have been previously described by several authors in the brain of vertebrates. In the telencephalon, ChATi neurons are seen in the co rtex, anterior dorsal ventricular ridge, basal ganglia, diagonal band, and bed nucleus of the stria terminalis. Further caudally, ChATi cell bodies are located in the preoptic area, hypothalamus, habenula, isth mus, and all motor efferent centers of the brainstem and spinal cord. Plexuses of ChATi fibers are observed in the areas containing choliner gic cell bodies. In addition, distinct plexuses are found in the corte x, the posterior dorsal ventricular ridge, the neuropiles of all prima ry visual centers of the diencephalon and mesencephalon, and several n on-visual nuclei of the brainstem. The distribution of ChAT immunoreac tivity in the brain of G. galloti resembles in many respects that of o ther vertebrates, and differences are mainly observed in the pretectum and midbrain tectum. Transverse segmental domains were identified in the brainstem and forebrain of Gallotia when the cranial nerve roots a nd fiber tracts were used as a reference, and most cranial motor nucle i were found to occupy the same segmental positions as have been repor ted in the chick.