Calle M et al. (2006), Effect of starvation on Fos and neuropeptide im...

XB-ART-34595

Gen Comp Endocrinol 2006 Jul 01;1473:237-46. doi: 10.1016/j.ygcen.2006.01.007.

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

Calle M , Kozicz T , van der Linden E , Desfeux A , Veening JG , Barendregt HP , Roubos EW .

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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.

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Species referenced: Xenopus laevis
Genes referenced: cartpt crh fos npy pomc ucn1

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	Fig. 1. Neurones in coronal sections of the brain of X. laevis, immunoreactive to Fos, in (A) the suprachiasmatic nucleus, (B) the cerebellum and (C) the ventral part of the Mg (MgV) of a representative control animal, and (D) in the MgV of a representative starved animal. In C and D, dorsal is not on top and orientation of dorsal (d)-lateral (l) has been indicated. Scale bar A,B = 50 μm, C,D = 20 μm.
	Fig. 2. Coronal sections at different levels of the Mg, in a representative control (left) and starved (right) animal, immunopositive for (A,B) CRF (in MgV), (C,D) CART (in MgM), (E,F) ENK (in MgM), and (G,H) Ucn1 (in MgV). Scale bar = 20 μm.
	Fig. 3. Coronal sections of a representative control (left) and starved (right) animal at the level of (A,B) the neural lobe of the pituitary gland, showing CART-ir fibers, (C,D) dorsomedial part of the suprachiasmatic nucleus with NPY-ir neurones, (E,F) ventromedial thalamic area with NPY-ir cells, and (G,H) Edinger–Westphal nucleus with CART-ir neurones. Scale bar = 20 μm.
	Fig. 4. Effect of starvation on mean diameter of neuronal perikarya profiles immunoreactive to ENK in the Mg subareas, MgV, MgM, and MgD, in (white bars) control animals and (black bars) starved animals. Values are expressed as means ± standard error of the mean (SEM). Asterisks indicate significant difference between control and starved animals (∗P < 0.05, ∗∗P < 0.001).