Central roles of GABA,glutamic acid decarboxylase (GAD) activity and mRNA GAD expression in the regulation of blood pressured and vasopressin release in sportaneous hypertensive rats (SHR)

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It is known that central amino acid (AA) plays important roles in the regulation of blood pressure and hormonal release. GABA suppresses a neural activity and glutamate (GLU) activates it. Thus, it is likely that the distortion of these AA release may affect the central regulation of blood pressure (BP) and vasopressin (AVP) release, thereby leading to hypertension.In the present study, in order to investigate central roles of AA in the development of hypertension in SHR,GABA and GLU release adjacent to the paraventricular nucleus were determined using a microdialysis method under osmotic and hemorrhagic stimuli in conscious SHR and normotensive rats (WKY), and BP and AVP release were also determined. Moreover, central changes in a glutamic acid decarboxylase (GAD) activity and GAD mRNA expression were determined in SHR and WKY.In intravenous administration of 2.5M NaCl, increases in plasma AVP levels and BP in SHR were greater than their increases in WKY,but central GABA release in SHR was smaller than it in WKY.GLU decreased in SHR and WKY.In hemorrhagic decreases in BP to the same extent, plasma AVP in SHR increased greater than it in WKY,but GABA and GLU decreased. There were no differences in them in SHR and WKY.A GAD activity and mRNA GAD expression in 11 week-old SHR were smaller than them in 11 week-old WKY.In conclusion, decreases in a GAD activity, its expression and GABA release might be related to the development of hypertension and enhanced AVP release in SHR.