Ischemia-induced development of cerebral edema in awake and anesthetized gerbils

A novel Na+ and Ca2+ channel blocker, T-477, prevents brain edema following microsphere-induced permanent occlusion of cerebral arterioles in rats

One of the most common acute complications of stroke is brain edema. Treatment of edema is recommended when the condition of the patients is deteriorating. The present study was undertaken to evaluate the effect of T-477 [(R)-(+)-2-(4-chlorophenyl)-2,3-dihydro-4-diethyl aminoacetyl-4H-1,4-benzorthiazine hydrochloride], a novel neuronal Na+ and Ca2+ channel blocker, on brain edema in rats. Cerebral ischemia was induced by intra-arterial infusion of 1000 microspheres into the forebrain of freely moving rats, resulting in brain edema. T-477 was intravenously infused continuously for 24 h or twice for 3 h with a 3-h interval between infusions immediately after microsphere injection. T-477 dose-dependently inhibited the increase in brain water content by both infusion procedures; the inhibition was statistically significant at doses of 25 mg/kg per 24 h and 14 mg/kg per 9 h. Additionally, infusion of T-477 at a dose of 14 mg/kg per 9 h significantly inhibited the decrease in K content and the increase in Ca content of the forebrain. In conclusion, T-477 prevents brain edema following microsphere-induced cerebral embolism in rats.

Time-dependent changes in the ischemic forebrain following the microsphere-induced permanent occlusion of cerebral arterioles in rats

To evaluate the progression of brain edema without modification by the effect of anesthetics, we examined the local and permanent ischemia model in unanesthetized rats. The forebrain embolism was induced by intra-arterial infusion of microspheres of 50-microm diameter in freely moving rats. From 2 to 48 hr following the injection, the water-, Na- and Ca-contents progressively increased while the K content decreased in the microsphere-injected hemisphere. After the 3rd day, the water- and Na-contents gradually decreased and returned to the normal level on the 14th day. In contrast, the Ca level remained elevated even on the 56th day. The animals showed signs of neurological deficits 24 hr after the injection. In histopathological examination, large infarct areas were present in the microsphere-injected hemisphere after 24 to 48 hr. One to two weeks later, the lateral ventricle was expanded. Eight weeks after the injection, the ventricle remained expanded and newly developed infarct areas were observed in a scattered pattern around the fibrotic area. The results show the close correlation between the development of edema and the increase/decrease of Na/K contents from the onset to the recovery from edema, and their changes are similar to those in human stroke. This model enables us to evaluate not only the acute ischemic insult but also the chronic changes of the forebrain following the stroke.

Protection of hippocampal neurons from ischemia-induced delayed neuronal death by hepatocyte growth factor: a novel neurotrophic factor

Hepatocyte growth factor (HGF), a natural ligand for the c-met protooncogene product, exhibits mitogenic, motogenic, and morphogenic activities for regeneration of the liver, kidney, and lung. Recently, HGF was clearly shown to enhance neurite outgrowth in vitro. To determine whether HGF has a neuroprotective action against the death of neurons in vivo, we studied the effect of HGF on delayed neuronal death in the hippocampus after 5-minute transient forebrain ischemia in Mongolian gerbils. Continuous postischemic intrastriatal administration of human recombinant HGF (10 or 30 micrograms) for 7 days potently prevented the delayed death of hippocampal neurons under both anesthetized and awake conditions. Even when HGF infusion started 6 hours after ischemia (i.e., in a delayed manner), HGF exhibited a neuroprotective action. We conclude that HGF, a novel neurotrophic factor, has a profound neuroprotective effect against postischemic delayed neuronal death in the hippocampus, which may have implications for the development of new therapeutic strategies for ischemic neuronal damage in humans.

Arachidonic acid metabolism in gerbil cerebra: effects of ischemia and pentobarbital

Pentobarbital pretreatment may be used to predict biochemical events involved in ischemic brain damage following bilateral carotid artery ligations in the gerbil, since it reduces the subsequent edema and mortality. The effects of this anesthetic on the ischemia-induced modifications of cerebral arachidonic acid metabolism were investigated, in order to correlate observed alterations with tissue damage. Cerebral lipids were radiolabeled in vivo with [3H]arachidonic acid prior to 10 min of cerebral ischemia and 0-120 min of perfusion. Ischemia stimulated a 97.3% increase in unesterified [3H]arachidonate, which was due to the loss of label from choline, inositol, and ethanolamine glycerophospholipids. Tissue reperfusion stimulated further reductions in [3H]choline and [3H]inositol glycerophospholipids, while ethanolamine glycerophospholipid and triglyceride labeling increased. Inositol glycerophospholipid, but not choline glycerophospholipid, labeling returned to control level by 60 min of reperfusion. Pentobarbital pretreatment reduced the accumulation of [3H]arachidonate by 56.2% during ischemia. It increased the recovery of [3H]ethanolamine glycerophospholipids during the ischemic period and [3H]choline glycerophospholipids during the first 5 min of reperfusion. These effects accounted for the reduction of unesterified [3H]arachidonate observed during ischemia and reperfusion.

Effects of cerebral ischemia and reperfusion on prostanoid accumulation in unanesthetized and pentobarbital-treated gerbils

Cerebral ischemia was induced in unanesthetized gerbils using bilateral carotid artery ligations. The effects of 20 min of global ischemia on the concentrations of prostaglandin F2 alpha (PGF2 alpha), PGE2, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 were determined after 0-24 h of reperfusion. Ischemia had little effect on eicosanoid production, but significant increases were observed by 5 min of reperfusion, with maximal levels reached by 15 min of reperfusion. PGF2 alpha was the most concentrated prostaglandin in postischemic brain, whereas PGE2 was most concentrated in control cerebra. Pretreatment with anesthetic doses of pentobarbital supported increased accumulation of PGF2 alpha in postischemic cerebra, increased accumulation of 6-keto-PGF1 alpha during the ischemic episode, and decreased accumulation of PGE2 at 120 min of reperfusion. It appears that the protective effects of barbiturate anesthesia are not expressed by the reduced accumulation of the above eicosanoids.