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

P. Jara , F. Rage (1) , M. Dorfman , D. Grouselle , R. Barra , S. Arancibia , H. E. Lara

1 IGMM - Institut de Génétique Moléculaire de Montpellier

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.

Mots clés: Animals *Cold Temperature Dizocilpine Maleate/administration & dosage/pharmacology Female Glutamic Acid/administration & dosage/*metabolism/physiology Injections; Intraventricular Neuroprotective Agents/administration & dosage/pharmacology Ovary/drug effects/*innervation Paraventricular Hypothalamic Nucleus/cytology/drug effects/*metabolism/physiology Rats Rats; Physiological/physiology Sympathetic Nervous System/drug effects/metabolism/*physiology Thyrotropin-Releasing Hormone/metabolism Up-Regulation/physiology; Sprague-Dawley Stress

Domaines: Biochimie, Biologie Moléculaire

P. Jara, F. Rage, M. Dorfman, D. Grouselle, R. Barra, et al.. Cold-induced glutamate release in vivo from the magnocellular region of the paraventricular nucleus is involved in ovarian sympathetic activation. Journal of Neuroendocrinology, 2010, 22 (9), pp.979--86. ⟨10.1111/j.1365-2826.2010.02040.x⟩. ⟨hal-02193574⟩