CONTROLLABLE GRADED CEREBRAL-ISCHEMIA IN THE GERBIL - STUDIES OF CEREBRAL BLOOD-FLOW AND ENERGY-METABOLISM BY HYDROGEN CLEARANCE AND P-31 NMR-SPECTROSCOPY

A technique for remotely controlling the degree of carotid artery occl usion in the gerbil model of cerebral ischaemia has been developed. Th e technique relies on manually adjustable nylon snares around the caro tid arteries, in conjunction with a computer-based monitoring system, to control the degree of occlusion. This has allowed us to determine t he dependence of energy metabolism (as assessed by P-31 NMR spectrosco py) on blood flow in greater detail than was possible in our previous studies. Data obtained show that energy changes first appear at flows of 25-30 mL/100 g/min, while at flows below 20 ml/100 g/min there is a major derangement of energy metabolism. The model was used to determi ne the sensitivity of cerebral energy metabolism to reduced cerebral b lood flow under normothermic conditions and in mild hypothermia (30-de grees-C). Hypothermia had a protective effect in that energy metabolit es were maintained at flows significantly below the normothermic thres hold.