Effect of starvation on Fos and neuropeptide immunoreactivities in the brain and pituitary gland of Xenopus laevis

Abstract

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 eVects of 16 weeks starvation on neurones immunoreactive (ir) to Fos and neuropeptides in various brain structures were quantiWed. 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 diVerences 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 diVerent eVects. 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 eVect 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-speciWc eVects 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.

Immunohistochemical localization of cocaine‐ and amphetamine‐regulated transcript peptide in the brain of the catfish, Clarias batrachus (Linn.)

“…This hypothesis is further supported by the extensive distribution of the CARTp-immunoreactive fibers in the neurohypophysis, proximal pars distalis, and the pars intermedia. CART mRNA has also been demonstrated in the goldfish hypothalamus and pituitary (Volkoff and Peter, 2001), and CARTp is present in the neural lobe of the frog hypophysis (Lázá r et al, 2004;Calle et al, 2006), and anterior lobe of the rat pituitary , emphasizing the importance of this peptide across different vertebrate groups in neuroendocrine regulation of the pituitary (Larsen et al, 2003;Smith et al, 2004Smith et al, , 2006.…”

“…(Meek and Nieuwenhuys, 1988) The Journal of Comparative Neurology. DOI 10.1002/cne cellular neurons of the frog (Lázá r et al, 2004;Calle et al, 2006), and also in a few neurons of the homologous pv subdivision of the NPO of C. batrachus. As opposed to tetrapods, the median eminence is absent in the teleosts, and the neurosecretory fibers including those from the NPO directly terminate hypophysial cells (Peter et al, 1990).…”

“…Despite information on the anatomical organization of CARTp in the mammalian brain, the presence and organization of CARTp and its functional significance in the brain of lower vertebrates is limited. CARTpimmunoreactivity is extensively distributed in the brain of frog, Rana esculenta (Lázá r et al, 2004), and reduced in magnocellular neurons and the pituitary of Xenopus laevis following prolonged starvation (Calle et al, 2006). Two different forms of CARTp with a differential distribution were reported in the goldfish brain (Volkoff and Peter, 2001).…”

Telencephalic Neuronal Activation Associated with Spatial Memory in the Terrestrial Toad <b><i>Rhinella arenarum:</i></b> Participation of the Medial Pallium during Navigation by Geometry

“…Bailey et al, 2002;Neal and Wade, 2007;Huang et al, 2013], as well as other amphibians (i.e. the salamander Plethodon shermani [Laberge et al, 2008] and Xenopus laevis [Calle et al, 2006]). Here we used a similar but somewhat modified procedure suitable for our study species [Daneri et al, unpubl.…”

About a snail, a toad, and rodents: animal models for adaptation research

“…These terminal types are neurochemically distinct because each type has its own set of neurochemical messenger (Van Wijk et al, 2010). Experimental evidence for differential control of MCN neurons comes from studies in which Xenopus was fasted for 3 weeks, leading to decreased amounts of CART, metenkephalin, and Ucn1 and to an increase in the amount of CRF (Calle et al, 2006b). These effects were especially obvious in the ventral part of the MCN and less pronounced in the medial and dorsal parts of the nucleus, suggesting a specialization of neuronal subpopulations within the MCN.…”