P049 RENOVASCULAR HYPERTENSIVE RATS (2K1C) HAVE REDUCED INTRACRANIAL COMPLIANCE INDUCED BY RAISED VENTRICULAR VOLUME COMPARED TO NORMOTENSIVE RATS

Background and Objective: Intracerebroventricular (ICV) infusions of increased volumes of saline can be used to study intracranial compliance (ICC). Since the two-kidneys,1-clip (2K1C) rat model of renovascular hypertension has an enhanced baseline level of intracranial pressure (ICP), the present study aimed to verify the effect of ICV infusions of 0.15 M NaCl on ICP and ICC in 2K1C rats. Methods: Male Holtzman rats (180-210 g) were randomly separated to be normotensive (NT; sham surgery, n = 5) or with 2K1C (n = 5), done by a partial left renal artery occlusion. Six weeks after, rats were anaesthetized with urethane (1.2 g/kg body weight, i.v.), tracheostomized, placed under artificial ventilation, and had an ICP sensor and a needle inserted into the lateral ventricle for, respectively, ICP recording and ICV 0.15 M infusions (30, 60 and 90 μL, at 100 μL/min). There was a 20-minute interval between each infusion. ICC was calculated by the ratio of volume change to ICP change [ICC = ΔV (μL)/Δ ICP (mmHg)]. Results: Baseline MAP, ICP, and P2/P1 ratio of 2K1C rats (166 ± 6 mmHg; 15.7 ± 1.7 mmHg; 1.6 ± 0.1, respectively) were higher than the ones in NT rats (94 ± 5 mmHg; 10.1 ±1.4 mmHg; 0.7 ± 0.1 respectively; p<0.05 vs 2K-1C). ICV infusions induced increased ICP in 2K1C rats (19 ±0.5; 42 ±1.2 and 55 ±5.5 mmHg, vs NT: 8 ±0.6; 25 ±3.2 and 36 ± 4.9 mmHg, respectively at 30, 60 and 90 μL infusion; p<0.05). In addition, 2K1C rats presented a reduced ICC only at 30 μl infusion (5.6 ±1.4, vs NT: 11.4 ±0.9; p<0.05). Conclusions: These findings suggest that renovascular hypertension impairs ICC to the well-documented increase in ICP. Support: FAPESP, CNPq.