Osmoregulation of the magnocellular neuroendocrine system during lactation.
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.
Summy-Long
J Y
JY
Department of Pharmacology, M. S. Hershey Medical Center, Pennsylvania State University, Hershey 17033, USA. js12@email.psu.edu
Gestl
S
S
Terrell
M L
ML
Wolz
G
G
Kadekaro
M
M
D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism* / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D007774:Lactation / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D009490:Neurosecretory Systems / Q000502:physiology*; D011247:Pregnancy; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D013495:Supraoptic Nucleus / Q000166:cytology / Q000378:metabolism; D014882:Water-Electrolyte Balance
D005227:Fatty Acids; D016760:Proto-Oncogene Proteins c-fos; D012462:Saline Solution, Hypertonic; D005947:Glucose