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

Department of Cell Biology, Faculty of Biology, University Complutense, Madrid, Spain.
Neuroscience Letters (Impact Factor: 2.06). 03/1998; 242(1):13-6. DOI: 10.1016/S0304-3940(98)00033-0
Source: PubMed

ABSTRACT 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.

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    ABSTRACT: Adrenomedullin (AM) is a novel neuropeptide with special significance in the mammalian hypothalamo-hypophysial axis. By using an antiserum specific for human AM, we have studied the localization of AM-like immunoreactive (AMi) cell bodies and fibers in the hypothalamus and hypophysis of the amphibians Rana perezi (anuran), Pleurodeles waltl (urodele), and Dermophis mexicanus (gymnophionan). Distinct AMi cell groups were found for each species. In the anuran, six cell groups were localized in the preoptic and infundibular regions, whereas only three and one were found in the urodele and gymnophionan, respectively. A comparative analysis of AMi cells and cells expressing arginine vasotocin (AVT), neuropeptide Y (NPY), and tyrosine hydroxylase (TH) revealed strong differences between species. Thus, colocalization of AVT/AM is most likely to occur in the preoptic magnocellular nucleus of urodeles and it is reflected by the intense AM immunoreactivity in the neural lobe of the hypophysis. Colocalization of NPY/AM seems to be possible in the suprachiasmatic nucleus of anurans. In the gymnophionan, cells containing AVT and NPY are distinct from AMi cells. Only in anurans, the ventral aspect of the suprachiasmatic nucleus possesses a small population of AMi cells that express also TH immunoreactivity and most likely also express NPY. The results strongly suggest that AM in amphibians plays an important regulatory role in the hypothalamo-hypophysial system, as has been demonstrated in mammals. On the other hand, substantial differences have been found between species with respect to the degree of colocalization with other chemical substances. Microsc. Res. Tech. 54:173–187, 2001. © 2001 Wiley-Liss, Inc.
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