LOCALIZATION OF ADRENOMEDULLIN-LIKE IMMUNOREACTIVITY IN THE HYPOTHALAMOHYPOPHYSEAL SYSTEM OF AMPHIBIANS

The presence of adrenomedullin-like immunoreactive (AMi) cell bodies a nd fibers in the hypothalamus and hypophysis of the amphibians Rana pe rezi (anuran) and Pleurodeles waltl (urodele) was examined by immunohi stochemistry. A large population of AMi neurons was found in the supra chiasmatic nucleus of both species. Differently, AMi cells in the magn ocellular nucleus of the preoptic area were only found in the urodele, whereas dispersed cells in the caudal infundibular region were exclus ively present in the anuran. This different staining pattern is reflec ted in the hypophysis where the neural lobe is primarily immunoreactiv e in the urodele while the labeling in the intermediate lobe prevailed in the anuran. The results strongly suggest that, as is mammals, the AM in amphibians may play an important regulatory role in the hypothal amo-hypophysial system. (C) 1998 Elsevier Science Ireland Ltd.