DISTRIBUTION OF CHOLINE-ACETYLTRANSFERASE IMMUNOREACTIVITY IN THE BRAIN OF ANURAN (RANA-PEREZI, XENOPUS-LAEVIS) AND URODELE (PLEURODELES WALTL) AMPHIBIANS

Because our knowledge of cholinergic systems in the brains of amphibia ns is limited, the present study aimed to provide detailed information on the distribution of cholinergic cell bodies and fibers as revealed by immunohistochemistry with antibodies directed against the enzyme c holine acetyltransferase (ChAT). To determine general and derived feat ures of the cholinergic systems within the class of Amphibia, both anu ran (Rana perezi, Xenopus laevis) and urodele (Pleurodeles waltl) amph ibians were studied. Distinct groups of ChAT-immunoreactive cell bodie s were observed in the basal telencephalon, hypothalamus, habenula, is thmic nucleus, isthmic reticular formation, cranial nerve motor nuclei , and spinal cord. Prominent plexuses of cholinergic fibers were found in the olfactory bulb, pallium, basal telencephalon, ventral thalamus , tectum, and nucleus interpeduncularis. Comparison of these results w ith those obtained in other vertebrates, including a segmental approac h to correlate cell populations, reveals that the cholinergic systems in amphibians share many features with amniotes. Thus, cholinergic ped unculopontine and laterodorsal tegmental nuclei could be identified in the amphibian brain. The finding of weakly immunoreactive cells in th e striatum of Rana, which is in contrast with the condition found in X enopus, Pleurodeles, and other anamniotes studied so far, has revived the notion that basal ganglia organization is more preserved during ev olution than previously though. (C) 1997 Wiley-Liss, Inc.