Effect of starvation on Fos and neuropeptide immunoreactivities in the brain and pituitary gland of Xenopus laevis.
In mammals complex interactions between various brain structures and neuropeptides such as corticotropin-releasing factor (CRF) and urocortin 1 (Ucn1) underlay the control of feeding by the brain. Recently, in the amphibian Xenopus laevis, CRF- and Ucn1-immunoreactivities were shown in the hypothalamic magnocellular nucleus (Mg) and evidence was obtained for their involvement in food intake. To gain a better understanding of the brain structures controlling feeding in X. laevis, the effects of 16 weeks starvation on neurones immunoreactive (ir) to Fos and neuropeptides in various brain structures were quantified. In the Mg, compared to controls, starved animals showed fewer neurones immunopositive for Fos (-55.9%), Ucn1 (-44.0%), cocaine and amphetamine-regulated transcript (CART) (-94.3%) and metenkephalin (ENK) (-65.0%), whereas CRF-ir neurones were 2.1 times more numerous. These differences were mainly apparent in the ventral part of the Mg, followed by the medial and dorsal part of the nucleus. In the neural lobe of the pituitary gland a 22.5% lower optical density of CART-ir was observed. In the four other brain structures investigated, starvation had different effects. The dorsomedial part of the suprachiasmatic nucleus showed 5.9 times more NPY-ir cells and in the ventromedial thalamic area a lower number of NPY-ir cells (-33.6%) was found, whereas the Edinger-Westphal nucleus contained fewer CART-ir cells (-42.2%); no effect of starvation was seen in the ventral hypothalamic nucleus. Our results support the hypothesis that in X. laevis, the Mg plays a pivotal role in feeding-related processes and, moreover, that starvation also has neuropeptide- and brain structure-specific effects in other parts of the brain and in the pituitary gland, suggesting particular roles of these structures and their neuropeptides in physiological adaptation to starvation.
Department of Cellular Animal Physiology, Institute for Neuroscience, Radboud University Nijmegen, Nijmegen, The Netherlands. m.calle@science.ru.nl
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M
Calle
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Kozicz
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van der Linden
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Desfeux
J G
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Veening
H P
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Barendregt
E W
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Roubos
D000818:Animals; D001069:Appetite Regulation; D001921:Brain / Q000378:metabolism*; D048429:Cell Size; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D007150:Immunohistochemistry; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009478:Neuropeptide Y / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D013217:Starvation / Q000378:metabolism*; D054832:Urocortins; D020651:Ventral Thalamic Nuclei / Q000166:cytology / Q000502:physiology; D014981:Xenopus / Q000502:physiology*; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D009419:Nerve Tissue Proteins; D009478:Neuropeptide Y; D009479:Neuropeptides; D016760:Proto-Oncogene Proteins c-fos; D054832:Urocortins; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D004744:Enkephalin, Methionine; C027511:enkephalin-Met, Arg(6)-Phe(7)-; D003346:Corticotropin-Releasing Hormone