Cold-induced glutamate release in vivo from the magnocellular region of the paraventricular nucleus is involved in ovarian sympathetic activation

We previously reported that centrally-induced sympathetic activation in response to cold stress is associated with a polycystic ovarian condition in rats, and thyrotrophin-releasing hormone (TRH) released locally from the magnocellular region of the paraventricular nucleus (PVN) appears to be involved in this activation. Because TRH neurones express NMDA glutamate receptors, in the present study, we investigated the role of glutamate in the increased release of TRH from magnocellular neurones induced by cold stress and its relationship to ovarian neurotransmission. Animals with a push-pull cannula stereotaxically implanted into the magnocellular portion of the PVN were exposed to cold stress (4 degrees C for 64 h) and subjected to intracerebral perfusion. Perfusate fractions were obtained and analysed by high-performance liquid chromatography to measure glutamate and GABA levels. Glutamate, but not GABA, release increased significantly in animals perfused under cold exposure. In vivo administration of glutamate to the PVN increased TRH release. Injection of MK-801 into the magnocellular portion of the PVN reduced ovarian noradrenaline turnover and led to an increase in catecholamine concentration from the adrenal glands and celiac ganglia. Taken together, the results obtained in the present study strongly suggest that glutamate release from the magnocellular PVN is sensitive to cold stress and that glutamate acts through the NMDA receptor to mediate cold-induced TRH release. This in turn triggers hypothalamic-ovarian pathway activation, which might be responsible for the polycystic condition induced by cold stress and other ovarian pathologies characterised by increased sympathetic discharge

L'activité de l'acétylcholinestérase musculaire est-elle corrélée à la concentration du Ca 2+

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Reconception durable de deux systèmes grandes cultures et légumiers pour réduire de moitié l’utilisation des produits phytosanitaires

Cette étude, conduite dans le cadre du dispositif DEPHY EXPE Ecophyto, sur une durée de six ans, vise à utiliser des leviers agronomiques et techniques en vue de réduire de 50 % l’utilisation des produits phytopharmaceutiques conventionnels dans deux systèmes de culture (grandes cultures et cultures légumières). Après cinq années d’expérimentation, la majorité des règles de décision ont été appliquées et la faisabilité de certains leviers mis en place a également été analysée. Ont également été identifiés des problèmes non résolus avec la technicité disponible, comme par exemple la maîtrise des bio-agresseurs du pois de conserve, le désherbage de l’oignon et la modulation des seuils de nuisibilité selon les niveaux de populations des auxiliaires. Les résultats mettent en évidence, en moyenne, des niveaux de performance moindres dans la conduite IFT50 (réduction de 50 % des IFT à l’échelle du système), avec des variations selon la culture et l’année considérée. Ces performances sont toutefois encourageantes et peuvent être améliorées afin d’optimiser l’apport de certains leviers.This study, conducted in the framework of the DEPHY EXPE Ecophyto dispositive, over a six-year period, aims at using agronomic and technical levers in order to reduce by 50 % the use of conventional phytopharmaceutical products in two cropping systems (arable and vegetable crops). After five years of experimentation, the majority of the expected technics were used and the application of some levers was analyzed. Some problems without solutions were identified, such as the control of bio-aggressors in canned peas, weeding in onion and modulation of thresholds regarding populations of auxiliaries. Results showed in average a lower performance of IFT50 conditions (reduced by 50% for treatments at the cropping system scale) that varies depending on the considered crop and year. However, the performances obtained are encouraging and can be further improved in order to optimize the benefits of certain levers