We recently reported that the ATI receptor antagonist, losartan, markedly decreases arterial pressure (AP) in sodium replete rats and that this response was attenuated in area postrema lesioned (APx) rats (Hypertension 26(3):558, 1995). In that study, food intake for the three week period following sham lesion was restricted to levels similar to that observed in APx rats. The 3 day average control AP was similar in sham (95 ± 3 mmHg) and APx (96 ± 3 mmHg) rats. These basal levels of AP are 10-15 mmHg lower than those observed in our laboratory in rats allowed free access to food. By day 1 of losartan infusion (10mg/kg/day), AP decreased to a significantly lower level in sham (80 ± 2 mmHg) compared to APx (90 ± 3 mmHg) rats. This trend was maintained through day 3 of losartan infusion where AP was significantly lower in sham rats (73 ± 2 mmHg), compared to APx rats (84 ± 2 mmHg). The present study was conducted to determine the extent to which the three week period of decreased food intake in APx and sham rats altered the hypotensive response to losartan. The above protocol was repeated in APx (N=3) and sham lesioned (N=4) rats 9-10 weeks following the 3 week recovery from APx or sham surgery. Control AP was similar in sham (100 ± 2 mmHg) and APx (103 ± 3 mmHg) rats. By day 1 of losartan, AP had decreased to the same level in APx (87 ± 4 mmHg) and sham (86 ± 1 mmHg) rats. AP continued to fall by day 3 of losartan in sham rats (77 ± 1 mmHg) but not APx (93 ± 5 mmHg) rats. These results demonstrate that the initial period of anorexia in APx rats, or food restriction in sham lesioned rats, lowers baseline AP and alters the temporal pattern of the hypotensive effects of losartan.
|Original language||English (US)|
|State||Published - Dec 1 1996|