Comparative analysis of adrenomedullin‐like immunoreactivity in the hypothalamus of amphibians

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.

Localization of Calbindin-D28k and Calretinin in the Brain of Dermophis Mexicanus (Amphibia: Gymnophiona) and Its Bearing on the Interpretation of Newly Recognized Neuroanatomical Regions

“…Most studies in gymnophionans have highlighted the great expansion of the hypothalamus, including the suprachiasmatic and preoptic regions, that in some cases was observed to be more distinctly organized into segregated cell groups than in urodeles Pinelli et al, 1997;Hilscher-Conklin et al, 1998;Ebersole and Boyd, 2000;Ebersole et al, 2001;Muñoz et al, 2001;Rastogi et al, 2001;López et al, 2006]. The present study has revealed that the distribution of CB and CR within this set of regions allows the distinction of most of the cell groups identified in anurans and urodeles [Milán and Puelles, 2000;Morona and González, 2008].…”

“…The distribution of CB and CR led us to consider the recently coined term supraoptoparaventricular region as a band between the preoptic area and the suprachiasmatic region that contains the magnocellular neurosecretory nucleus and stains distinctly for other markers González and Smeets, 1997;Hilscher-Conklin et al, 1998;Muñoz et al, 2001;López et al, 2007]. This band is histogenetically distinctly specified during development in a manner that has been shown to be constant at least for tetrapods [Bardet et al, 2008].…”

Possible Role of Nitric Oxide and Adrenomedullin in Bipolar Affective Disorder

“…AM immune reactivity is present in the brain, consistent with a role as neurotransmitter [5]. AM induces vasorelaxation by activating adenylate cyclase and also by stimulating the release of NO [6].…”

Pathophysiological role of nitric oxide and adrenomedullin in autism

“…AM immune reactivity is present in the brain and is consistent with a role as a neurotransmitter. 18 AM induces vasorelaxation by activating adenylate cyclase, and also by stimulating the release of NO. 19 NO and AM function in the regulation of the hypothalamo-neurohypophysial system and HPA.…”