The effect of prolonged recovery on the hypotensive responses to losartan in area postrema lesioned and sham rats

We recently reported that the AT1 receptor antagonist, losartan, markedly decreases arterial pressure (AP) in sodium replete rats and that this response is attenuated in area postrema lesioned (APx) rats (Hypertension 26(3):558, 1996). In that study, food intake for the three week period following sham lesion was restricted to levels similar to that observed in APx rats. These food restricted sham rats had lower mean arterial pressures and attenuated responses to losartan, as compared to control rats fed ad libitum. The present study examined whether these differences persisted months, rather than weeks after APx or sham lesions. The above protocol was repeated in APx and two groups of sham lesioned rats 3 months following APx or sham surgery. The first sham operated group was food restricted (SFR) for three weeks following surgery, while the second sham operated group was allowed ad libitum (SAL) access to food. The results were as follows: Change in MAP (mmHg) Days of Losartan N. Control 2, 4 6 8 10 APx 8 105±3 -10±3 -21±4 -24±4 -17±4 -18±6 SFR 7 105±3 -19±2 -26±2 -22±3 -37±5* -28±5 SAL 5 111±4 -23±4* -22±4 -28±4 -31±6* -29±4 * denotes statistical significance as compared to APx (p<0.05) As both sham groups responded similarly to losartan (yet significantly different than APx rats), these results demonstrate that transient decreases in food intake do not affect the response to losartan if rats are allowed an adequate recovery period.