[Vasopressin facilitates aortic baroreceptor activity in the rat]

Effect of arginine vasopressin (AVP) on the aortic baroreceptor activity of anesthetized rats was studied in 25 aorta arch-aortic nerve preparations. The results obtained were as follows: (1) By perfusing the isolated aortic arch with AVP (10(-8) mol/L), at constant intra-aortic pressure (IAP) of 13.3 kPa, the integrated aortic nerve activity (IANA) was increased by 40 +/- 4.7% (P < 0.0001), and the stepwise increase or decrease of IAP were accompanied correspondingly by changes of IANA. The function curve of aortic baroreceptor was shifted to the left and upward, and the peak into grated value (PIV) of the curve was increased from 621 +/- 85 to 711 +/- 81%.kPa-1 (P < 0.01). There were no changes in threshold pressure (TP), saturation pressure (SP), operating range (OR) and peak slope (PS). After washing out of AVP, the IANA returned to the control level. (2) The above effects of AVP were abolished by pretreatment with V1-antagonist [d (CH2)5Tyr- (Me) AVP, 10(-7) mol/L]. (3) By perfusing the aorta-arch preparation with five different concentrations of AVP (10(-11)-10(-7) mol/L), at the same constant IAP, IANA were respectively 190%, 160%, 150%, 130% and 103% of the control. After pretreatment with V2-antagonist [d (CH2) (d-Ile2Abu4] AVP (10(-7) mol/L), the perfusions with five different concentrations of AVP increased the IANA respectively to 130%, 150%, 160%, 170% and 180% of the control. When the V2-receptor-mediated vasodilating effect of AVP was blocked, the facilitatory effect of AVP on aortic baroreceptors via V1 receptors was significantly exhibited in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)