Serotonin is important for effective renal blood flow (RBF) autoregula
tion in the normal rat and at two or seven days of reperfusion followi
ng renal ischemia. It has been suggested that after these reperfusion
periods and during renal perfusion pressure (RPP) lowering, the vasodi
latory autoregulation mechanism is not damaged but overwhelmed by incr
eased 5-HT2-mediated vasoconstriction, resulting: in complete loss of
autoregulation. This study analyzes the influence of the 5-HT2- antago
nist ketanserin on RBF autoregulation after two hours or one day of re
nal reperfusion following ischemia and in a model of cyclosporine (20
mg/kg/day for 10 days)-induced nephrotoxicity. Autoregulation was lost
both after brief reperfusion periods and after cyclosporine. Similar
to the two or seven days of reperfusion experiments, ketanserin in the
cyclosporine model led to reappearance of autoregulation down to RPP
95 mm Hg. Despite an increased response to intrarenal serotonin after
two hours of reperfusion, autoregulation was not restored by ketanseri
n, ht one day of reperfusion and with ketanserin. autoregulation was p
resent down to 105 mm Hg. Thus, during the early reflow period, other
factors (of decreasing importance) most likely add to autoregulation l
oss.