[Effects of atrial natriuretic peptide on aortic baroreceptor activity in rats]

Effects of atriopeptin III (AP III) on the aortic baroreceptor activity in rats were studied in the isolated aorta arch-aortic nerve preparation in situ. By perfusing the isolated aortic arch with AP III (2.0 micrograms/ml) in rats, at constant intra-aortic pressure (IAP) of 13.3 kPa, the integral of aortic nerve activity (IANA) was increased by 64 +/- 27% (P < 0.001), the stepwise increases and decreases of IAP were correspondingly accompanied by increase and decrease in IANA, while the saturation pressure (SP) and the operating range (OR) of aortic baroreceptor activity were decreased from 22.5 +/- 0.5 to 21.3 +/- 0.5 kPa (P < 0.05) and 12.1 +/- 0.4 to 10.6 +/- 0.4 (P < 0.05), respectively, and the threshold pressure (TP) did not show any changes. The function curve of aortic baroreceptor was shifted to left and upward, and the peak integral value (PIV) and the peak slope (PS) of the curve were increased from 508 +/- 66 to 730 +/- 52% (P < 0.05), 55.6 +/- 7.5 to 93.2 +/- 6.8%.kPa-1 (P < 0.05), respectively. After washing out of AP III, the IANA returned to the control level. By perfusing the aortic arch with sodium nitroprusside (NP, 1.0 microgram/ml), at constant intra-aortic pressure (IAP) of 13.3 kPa, although the IANA was decreased as compared with the control, there was no statistical significance (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)