Effects of Cerebroprotective Agents on Cerebral Blood Flow and on Postischemic Energy Metabolism in the Rat Brain

Abstract

Summary: Male Wi star rats were subjected to forebrain ischemia of lO min duration by clamping both common carotid arteries and simultaneously lowering systemic blood pressure to 40 mm Hg by exsanguination. Re covery was achieved by removing the arterial clamps and reinfusing the blood. Cortical levels of high-energy phos phates and glycolytic substrates were determined enzy matically. Naftidrofuryl (10 or 20 mg/kg i.p.) or ketamine (5 mg/kg i.v.) were applied 30 min prior to the induction of ischemia. S(-)-Emopamil (4 mg/kg) or nimodipine (50 fLg/kg) were administered by intravenous infusion over 30 min. Nimodipine and emopamil increased the blood glu cose level and lowered preischemic blood pressure. Under control conditions, a tendency toward a higher cortical glucose level was observed in treated brains. Brain energy stores were exhausted after ischemia in control and treated animals to the same degree. Lactate levels, however, were higher in emopamil-treated an imals. This effect was attributed to the elevated pre ischemic glucose levels. During the early recovery pe riod, the restoration of high-energy phosphates was ac-A variety of the so-called cerebroprotective agents have been shown to ameliorate brain energy metabolism under hypoxic or ischemic conditions (Dirks et aI., 1984; Karcher et aI., 1984; Proctor et aI., 1984; Rachman et aI., 1984; Heffez and Passon neau, 1985;Krieglstein and Weber, 1986). The ef fects include, among others, increases in the level 480celerated by both calcium entry blockers. Nimodipine and emopamil increased the levels of glucose and glu cose-6-phosphate in the early postischemic period. Nafti drofuryl (10 mg/kg) increased the level of creatine-phos phate and ATP after 2 min of recovery. Naftidrofuryl (20 mg/kg) exerted no effect on cerebral energy metabolism, but considerably reduced postischemic blood pressure (possibly thereby masking its ameliorative action). Keta mine accelerated the postischemic restoration of high-en ergy phosphates. In the conscious rat, local cerebral blood flow (LCBF) was determined with the 14C-iodoan tipyrine technique following emopamil (20 mg/kg s.c.) or naftidrofuryl (10 mg/kg i.v.) application. Both com pounds increased LCBF values in the majority of grey matter structures. It was concluded that the cerebropro tective agents investigated share an accelerating effect on the postischemic restoration of high-energy phosphates in cerebral cortex. Key Words: Cerebral blood flow Cerebroprotective agents-Energy metabolism-Isch emia-Rat brain.of creatine-phosphate, ATP, glucose, and glucose-6-phosphate, as well as reduced ADP, AMP, and lactate levels. The interest mainly centers on the high-energy phosphates ATP and creatine-phos phate, as these substrates are essential for the maintenance of cellular function. A faster postisch emic restoration of these substrates, therefore, should improve the functional recovery of brain tissue. In the present study, compounds from dif ferent classes of drugs were investigated to eval uate whether or not they sh...

Effects of Phenylalkylamine Calcium Entry Blockers on Postischemic Energy Metabolism in the Isolated Perfused Rat Brain: Stereoselectlive Action of Emopamil

“…and emopamil are in accordance with earlier observations [Bielenberg ct al., 1987a;Krieglstein and Weber, 1986;Weber and Krieglstein, 1985], The re sults are further confirmed by observations that emopamil and nimodipinc accelerate the restoration of high-energy phosphates in the artificially ventilated rat following 10 min of ischemia [Bielcnberg ct al., 1987b]. The increased level of glucose-6-phosphate following emopamil administra tion is also consistent with earlier findings in the isolated perfused rat brain [Bielenberg et al, 1987a], This effect has been documented as well in the artificially ventilated rat for emopamil and nimodipinc [Bielenberg et al. 1987b],…”

Naftidrofuryl Protects Neurons against Ischemic Damage

“…In accord with these results, Bielenberg et al [12] described increased postischemic creatine phos phate and ATP levels in rat brains in vivo caused by 10 mg/kg i.p. naftidrofuryl, whereas a higher dose (20 mg/kg i.p.)…”

“…Therefore, it seemed to be of some significance whether naftidrofuryl could change the LCBF during the early postischemic period. In addition, it has already been shown that naftidrofuryl elevated the cortical ATP level 2 min after ischemia probably because of its blood flow increasing activity in cortical tissue [ 12], Further more, we found a postischemic increase in LCBF of rat cortical tissue caused by calcium antagonists only 2 min after ischemia in the same experimental model [13,14], Thus, it seemed to be advisable to determine LCBF in this study 2 and 10 min after ischemia. As the present results of the LCBF measurements elucidate, the post ischemic blood flow is not generally enhanced by nafti drofuryl.…”

“…It may be argued that this higher dose of naftidrofuryl causes an extracerebral steal effect by general vasodilation. This information prompted us to use 10 mg/kg naftidrofuryl for the experiments presented in this study the more because we knew that this dose still caused a consider able increase in preischemic LCBF of rat brain in vivo [ 12].…”

Postischemic (S)-emopamil therapy ameliorates focal ischemic brain injury in rats.

“…1718 Like many other calcium channel blockers, (S)-emopamil is a potent cerebral vasodilator, capable of increasing cortical blood flow by 50% or more 19 . 20 without affecting local cerebral glucose utilization.…”