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  • Title: Osmoregulation of the magnocellular neuroendocrine system during lactation.
    Author: Summy-Long JY, Gestl S, Terrell ML, Wolz G, Kadekaro M.
    Journal: Am J Physiol; 1997 Jan; 272(1 Pt 2):R275-88. PubMed ID: 9039019.
    Abstract:
    Glucose utilization and Fos expression were used to compare responses of cerebral structures involved in osmoregulation in virgin and lactating rats given 0.15, 0.85, or 1.5 M NaCl subcutaneously. In virgin animals, glucose utilization increased (P < 0.05) in the supraoptic nuclei (SON), paraventricular nuclei (PVN), and neural lobe (NL) proportionally to the osmotic stimulus (0.15 M NaCl < 0.85 M NaCl < 1.5 M NaCl), whereas metabolism in the median preoptic nucleus (MPO) and median eminence (ME) increased only after 1.5 M NaCl. In lactating rats, enhanced utilization of glucose in response to osmotic stimulation was absent in the PVN (0.85 M NaCl), MPO, and ME or significantly (P < 0.01) reduced (SON, PVN, NL) compared with virgin animals. Glucose utilization in each structure correlated linearly with plasma osmolality but with a lower slope (P < 0.05) in lactating animals. Magnocellular neurons expressing Fos in the SON increased linearly with plasma osmolality and were more numerous (P < 0.05) in control lactating animals but increased less (P < 0.05) than in virgin rats after 0.85 M NaCl. The attenuated magnocellular response during lactation results from reduced afferent activation from osmosensitive forebrain sites.
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