Osmoregulation of the magnocellular neuroendocrine system during
lactation.
Summy-Long, J. Y., S. Gestl, M. L. Terrell, G. Wolz, and M. Kadekaro.
Department of Pharmacology or Department of Obstetrics and
Gynecology, M.S. Hershey Medical Center, The Pennsylvania State
University, Hershey, PA 17033; Division of Neurosurgery, University
of Texas Medical Branch, Galveston, TX, 77555
APStracts 3:0245R, 1996.
Glucose utilization and Fos expression were used to compare responses
of cerebral structures involved in osmoregulation in virgin and
lactating rats given 0.15M, 0.85M or 1.5M NaCl, sc. 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 (0.15M NaCl < 0.85M
NaCl < 1.5M NaCl) whereas metabolism in the median preoptic
nucleus (MPO) and median eminence (ME) increased only after 1.5M
NaCl. In lactating rats, enhanced utilization of glucose in response
to osmotic stimulation was absent in the PVN (0.85M 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, were more numerous
(p<0.05) in control lactating animals but increased less
(p<0.05) than in virgin rats after 0.85M NaCl. The attenuated
magnocellular response during lactation results from reduced afferent
activation from osmosensitive forebrain sites.
Received 21 February 1996; accepted in final form 12 June 1996.
APS Manuscript Number R103-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96