Involvement of N-methyl-D-aspartic acid receptor activation in oxytocin and vasopressin release after osmotic stimuli in rats.
The present study aimed to examine roles of N-methyl-D-aspartic acid (NMDA) receptors in oxytocin and vasopressin release after osmotic stimuli. A noncompetitive NMDA receptor antagonist, MK-801 (0.2 mg/kg body weight, i.p.), significantly decreased plasma concentrations of oxytocin and vasopressin after hypertonic saline injection (0.3 or 0.6 M NaCl, i.p., 20 ml/kg). By contrast, oxytocin release induced by injection of cholecystokinin octapeptide (20 microg/kg, i.p.) was not significantly changed by MK-801. Hypertonic saline injection increased the number of cells expressing Fos in the supraoptic nucleus and in the regions anterior and ventral to the third ventricle (AV3V) regions [the organum vasculosum of the lamina terminalis (OVLT) and median preoptic nucleus]. MK-801 decreased the number of cells expressing protein in these areas after hypertonic saline injection. A microdialysis method showed that a hypertonic saline injection (0.6 M NaCl, 20 ml/kg, i.p.) facilitated glutamic acid release in and near the OVLT. The results support the view that NMDA receptor in the AV3V region modulates in a facilitative fashion the AV3V inputs to the supraoptic neurosecretory neurones.
Onaka
T
T
Department of Physiology, Jichi Medical School, Minamikawachi-machi, Tochigi-ken, Japan. tonaka@jichi.ac.jp
Yagi
K
K
D000818:Animals; D002766:Cholecystokinin / Q000494:pharmacology; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D007274:Injections, Intraperitoneal; D009994:Osmolar Concentration; D010121:Oxytocin / Q000097:blood / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D014667:Vasopressins / Q000097:blood / Q000378:metabolism*
D018691:Excitatory Amino Acid Antagonists; D016760:Proto-Oncogene Proteins c-fos; D016194:Receptors, N-Methyl-D-Aspartate; D012462:Saline Solution, Hypertonic; D014667:Vasopressins; D018698:Glutamic Acid; D010121:Oxytocin; D016291:Dizocilpine Maleate; D002766:Cholecystokinin