Localization of adrenomedullin-like immunoreactivity in the hypothalamo-hypophysial system of amphibians.

The presence of adrenomedullin-like immunoreactive (AMi) cell bodies and fibers in the hypothalamus and hypophysis of the amphibians Rana perezi (anuran) and Pleurodeles waltl (urodele) was examined by immunohistochemistry. A large population of AMi neurons was found in the suprachiasmatic nucleus of both species. Differently, AMi cells in the magnocellular nucleus of the preoptic area were only found in the urodele, whereas dispersed cells in the caudal infundibular region were exclusively present in the anuran. This different staining pattern is reflected in the hypophysis where the neural lobe is primarily immunoreactive 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 hypothalamo-hypophysial system.