Cardiovascular changes induced by central hypertonic saline are accompanied by glutamate release in awake rats.
To elucidate neurochemical mechanisms responsible for cardiovascular responses induced by central salt loading, we directly perfused the paraventricular nucleus (PVN) of the hypothalamus region with hypertonic saline (0.3 or 0.45 M) by using an in vivo brain microdialysis technique. We then measured the extracellular concentrations of glutamate in the PVN region in conscious rats along with the blood pressure and heart rate. Blood pressure, heart rate, and glutamate levels were increased by perfusion of 0.45 M saline; however, they did not change by perfusion of 0.3 M saline. Next, we examined the possible involvement of glutamate in the cardiovascular responses induced by hypertonic saline. Dizocilpine, a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, attenuated the increases of blood pressure and heart rate, although 6-cyano-7-nitroquinoxaline-2,3-dione, an antagonist of the non-NMDA receptor, did not affect the blood pressure and heart rate. Our results show that local perfusion of the hypothalamic PVN region with hypertonic saline elicits a local release of glutamate, which may act via NMDA-type glutamate receptors to produce cardiovascular responses.
Jin
Q H
QH
Department of Physiology, Miyazaki Medical College, Miyazaki 889 - 1692, Japan.
Ueda
Y
Y
Ishizuka
Y
Y
Kunitake
T
T
Kannan
H
H
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D016291:Dizocilpine Maleate / Q000008:administration & dosage; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage; D005110:Extracellular Space / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D008353:Mannitol / Q000008:administration & dosage; D017551:Microdialysis; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage*; D014851:Wakefulness
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D012462:Saline Solution, Hypertonic; D018698:Glutamic Acid; D008353:Mannitol; D016291:Dizocilpine Maleate