Seasonal variations of the beta-endorphin neuronal system in the mediobasal hypothalamus of the jerboa (Jaculus orientalis).
ABSTRACT The distribution of neurons expressing beta-endorphin immunoreactivity was explored in the brain of adult jerboa during two distinct periods characterizing its reproductive cycle. A large presence of cell bodies displaying beta-endorphin immunoreactivity occured within different parts of the mediobasal hypothalamus along its rostrocaudal extent, from the retrochiasmatic area to the posterior arcuate nucleus. Quantitatively, the highest density of immunoreactive beta-endorphin neurons was noted at the medial level of the arcuate nucleus. Furthermore, a seasonal study showed that the number of IR-beta-endorphin neurons was highest in the anterior portion of the arcuate nucleus of jerboas sacrificed in autumn as compared to those sacrificed during spring-summer. Quantitatively, the number of beta-endorphin containing neurons in autumn was 200% in comparison to that found in spring-summer. These results suggest that beta-endorphin containing neuronal population especially localized in the anterior part of arcuate nucleus, exerts an inhibitory influence on the GnRH neurosecretory system in the jerboa, notably in autumn, probably via an increasing expression of its products. The results provide morphofunctional arguments in favour of inhibitory opioid control of GnRH neurons activity and hence the neuroendocrine events regulating reproduction in jerboa.
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ABSTRACT: The mu-opioid receptor (MOR) is expressed in bovine, human, equine and canine oocytes, and in seasonal breeders, it is expressed with higher intensity during the anoestrous phase. Supplementation of in vitro maturation (IVM) medium with opioid agents, agonists or antagonists, was shown to affect oocyte maturation in several species such as rat, bovine and equine. This study reports the effects of supplementing IVM medium with naloxone (Nx), an opioid antagonist, on nuclear and cytoplasmic maturation rate of oocytes recovered from anoestrous bitches. Cytoplasmic maturation was examined in terms of mitochondrial (mt) distribution. In order to confirm the receptor-mediated action of Nx, in oocytes of anoestrous bitches, MOR expression was analyzed by Western blot. Cumulus-oocyte complexes, recovered from the ovaries of bitches in anoestrous, were cultured in vitro and Nx was added at the concentrations of 1 x 10(-6), 1 x 10(-8) and 1 x 10(-10) M. The rate of oocytes resuming meiosis after culture in presence of 1 x 10(-6) M Nx (29%) was significantly higher than that of oocytes of control group (12%; p < 0.05). However, treatment with Nx did not affect mt distribution pattern. In denuded oocytes and in corresponding cumulus cells, a doublet of 65 and 50 kDa was observed. We conclude that, in oocytes of anoestrous bitches, MOR is expressed and Nx significantly improves nuclear maturation rate. Further studies should be performed to elucidate the expression of other opioid receptors, such as delta and kappa, and possible interactive effects of their antagonists on canine oocyte maturation.Reproduction in Domestic Animals 07/2009; 44 Suppl 2:263-8. · 1.39 Impact Factor
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ABSTRACT: The control of appetite and satiety is extremely complex and involves a balance between neurotransmitters and neuropeptides to stimulate and/or inhibit feeding behaviour. The effect of cannabinoids on food intake is well established, but little is known about the mechanism of action underlying their activity. In the present report, the effect of pharmacological manipulation of the cannabinoid receptor on the expression of hypothalamic neuropeptides is investigated. We used an immunohistochemical approach to examine the effect of intracerebroventricular administration of the cannabinoid receptor agonist WIN55,212-2 and the inverse agonist AM251 on neuropeptide Y (NPY) and the β-endorphin (β-end) neuronal hypothalamic systems. Double immunohistochemistry (c-fos/β-end) was used to assess the number of β-end neurons activated by the cannabinoid agonist. The present results showed that 1 μg WIN 55,212-2 increases β-end immunoreactivity within the arcuate nucleus while no significant changes were noted in the NPY-immunoreactive nerve fibres network in comparison to the control group. Injection of 1 μg AM251 decreases both NPY and β-end immunoreactivity within the arcuate nucleus. The number of β-end neurons exhibiting c-fos increased significantly in WIN 55,212-2 compared with the control group. These results suggest that cannabinoids affect the expression of hypothalamic neuropeptides, notably the NPY and β-end systems, which may have implications in the orexigenic action of cannabinoids.The British journal of nutrition 02/2011; 105(4):654-60. · 3.45 Impact Factor
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ABSTRACT: The jerboa is a semi-desert rodent, in which reproductive activity depends on seasons, being sexually active in spring-summer. The aim of this study was to determine whether expression of two RF-amide peptides recently described to regulate GnRH neuron activity, kisspeptin (Kp) and RFRP-3, displays seasonal variation in jerboa. Kp and/or RFRP-3 immunoreactivity was investigated in the hypothalamus of jerboas captured in the field of the Middle Atlas mountain (Morocco), either in spring or autumn season. As in other rodents the kp-immunoreactive (ir) neurones were found in the anteroventro-periventricular and arcuate nuclei. RFRP-3 neurones were noted within the dorso/ventro medial hypothalamus. A marked sexual dimorphism in the expression of Kp, but not RFRP-3 was observed. The number of Kp- immunoreactive (ir) neurones was nine times greater, and the density of Kp-ir fibres and terminal-like elements in the median eminence was two times higher in females than in males. Furthermore, a significant seasonal variation in peptide expression was obtained with an increase in both Kp- and RFRP- 3- ir cell bodies in sexually active male jerboas captured in spring as compared to sexually inactive autumn animals. In the arcuate nucleus, the level of Kp-ir cells and fibres were significant higher during the sexually active period in spring than during the autumnal sexual quiescence. Similarly, the number of RFRP-3 ir neurones in the ventro/dorsomedial hypothalamus was about 3 times higher in sexually active jerboa captured in spring as compared to sexually inactive autumn animals. Altogether, our study reports the distribution of kp and RFRP-3 neurones in the hypothalamus of a desert species and reveals a seasonal difference in their expression which correlates with sexual activity. These findings suggest that these two RF-amide peptides may act in concert to synchronize jerboa's gonadotropic activity with the seasons. © 2013 British Society for Neuroendocrinology.Journal of Neuroendocrinology 01/2013; · 3.51 Impact Factor