Dehydroepiandrosterone (DHEA) reduces neuronal injury in a rat model of global cerebral ischemia

Introduction: Many studies report an inverse correlation between levels of DHEA and neurological diseases. Exogenous DHEA protects hippocampal neurons against excitatory amino acid induced neurotoxicity. The purpose of this experiment is to evaluate the effect of DHEA in an animal model of transient but severe forebrain ischemia. Methods: At thirteen days prior to induction of ischemia, male Wistar rats were implanted with various doses of DHEA-placebo, 25 mg, 50 mg or 100 mg. Forebrain ischemia was induced for 10 min using a modified four-vessel occlusion technique, with hippocampal neuronal injury assessed at 7 days post-ischemically and expressed as a percentage of total cells. Results: Both normal and necrotic hippocampal CA(1) cells were counted. Percentages of hippocampal injury observed were 88+/-13% in animals treated with placebo, 84+/-8% in the 25 mg DHEA group, and 60+/-7% in the 50 mg DHEA group. Animals treated with 100 mg DHEA displayed a significant (P<0.05) reduction of hippocampal CA(1) cell injury at 60+/-7% Conclusion: Treatment with a high dose, but not a low or moderate dose, of DHEA implantation reduces hippocampal CA(1) neuronal injury following severe but transient forebrain ischemia.     

Green tea polyphenol (-)-epigallocatechin gallate reduces neuronal cell damage and up-regulation of MMP-9 activity in hippocampal CA1 and CA2 areas following transient global cerebral ischemia

Previous studies have demonstrated that (-)-epigallocatechin gallate (EGCG), a green tea polyphenol, protects against ischemia and reperfusion-induced injury in many organ systems. Here, we test the hypothesis that part of EGCG's neuroprotective effects may involve a modulation of matrix metalloproteinases (MMPs) after cerebral ischemia. C57BL/6 mice were subjected to 20 min of transient global cerebral ischemia. EGCG (50 mg/kg) or vehicle (saline) was administered i.p. immediately after ischemia. Brains were examined 3 days after ischemia. The effects of EGCG on MMP (gelatinase) activity and neuronal damage in the hippocampus were assessed. Gelatin gel zymography showed induction of active forms of MMP-9 protein after transient global cerebral ischemia. In situ zymography showed that ischemic gelatinase activity occurred primarily in pyramidal neuronal areas after brain ischemia. Mice treated with EGCG showed significantly reduced gelatinase levels. Neuronal damage was evident in CA1 and CA2 pyramidal sectors, corresponding to TUNEL-positive signals. In EGCG-treated mice, delayed neuronal damage was significantly reduced compared with vehicle-treated mice. These results demonstrate that the green tea polyphenol EGCG suppresses MMP-9 activation and reduces the development of delayed neuronal death after transient global cerebral ischemia in mouse brain.     

Inhibition of Na(+)-K(+)-Cl(-) cotransporter during focal cerebral ischemia decreases edema and neuronal damage

Our previous study demonstrated that pharmacological inhibition of the Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) during ischemia and reperfusion attenuated neuronal damage and edema. In this study, we further investigated whether NKCC1 activity contributes to ischemic damage during either ischemia or reperfusion. Immunoblotting revealed that expression of NKCC1 protein was increased following 2-h focal ischemia in cerebral cortex. A sustained up-regulation of NKCC1 in cortex was detected at 4, 8, 12, and 24 h of reperfusion. An increase in the phosphorylated NKCC1 (NKCC1-p) was found at 4 and 8 h of reperfusion. In striatum, a significant increase in NKCC1 expression occurred between 4 and 24 h of reperfusion and no elevation of NKCC1-p signal was observed. Artificial cerebral spinal fluid (aCSF) or 100 microM bumetanide in aCSF were continuously microdialyzed into left cortices either 1 h prior to ischemia plus 2-h ischemia, or only during 24-h reperfusion. Infarction volume was significantly decreased in the pre-ischemic bumetanide-treated group (P<0.05) but not in the post-ischemic treatment group (P>0.05). In addition, pre-ischemic bumetanide treatment reduced the ipsilateral water content increase by 70% (P<0.05). Inhibition of NKCC1 did not attenuate poly (ADP-ribose) polymerase cleavage or the number of TUNEL-labeled apoptotic cells in ischemic brains. These results suggest that inhibition of NKCC1 attenuates cytotoxic edema and necrotic neuronal death during focal ischemia. Activation of NKCC1 activity plays a role in the early stage of ischemic damage.     

Post-ischemic modest hypothermia (35 degrees C) combined with intravenous magnesium is more effective at reducing CA1 neuronal death than either treatment used alone following global cerebral ischemia in rats

In this study, we investigated the efficacy of pre- and 2 h post-ischemic magnesium treatment with different durations of modest hypothermia (35 degrees C) induced immediately or 2 h following global cerebral ischemia in rats. In experimental group 1, rats received an intravenous loading dose (LD) of 360 micromol/kg MgSO4 immediately before ischemia followed by a 48 h intravenous infusion (IVI) at 120 micromol/kg/h. Immediately post-ischemia, body temperature was lowered to 35 degrees C for 6 h or maintained at 37 degrees C. In experimental group 2, 2 h after ischemia, rats received the MgSO4 LD/IVI and/or had their body temperature lowered to 35 degrees C for 6, 12 or 24 h. In experimental group 1, ischemic rats receiving 6 h of modest hypothermia demonstrated 9.4% CA1 neuronal survival, whereas rats treated with magnesium alone or magnesium and 6 h of modest hypothermia demonstrated 5.1% and 37.9% neuronal survival, respectively. In experimental group 2, ischemic rats receiving 6, 12 or 24 h of modest hypothermia demonstrated 6.1, 5 and 43% CA1 neuronal survival, respectively. Rats treated with magnesium and 6, 12 or 24 h of modest hypothermia demonstrated 8.1, 9 and 76% neuronal survival, respectively. Our findings demonstrate that post-ischemic treatment with a 24 h duration of modest hypothermia and magnesium is more effective than either treatment used alone.     

Effects of LF 16-0687 Ms,a bradykinin B(2) receptor antagonist,on brain edema formation and tissue damage in a rat model of temporary focal cerebral ischemia

Bradykinin, an endogenous nonapeptide produced by activation of the kallikrein–kinin system, promotes neuronal tissue damage as well as disturbances in blood–brain barrier function through activation of B₂ receptors. LF 16-0687 Ms, a non-peptide competitive bradykinin B₂ receptor antagonist, was recently found to decrease brain swelling in various models of traumatic brain injury. We have investigated the influence of LF 16-0687 Ms on the edema formation, neurological outcome, and infarct size in temporary focal cerebral ischemia in rats. Sprague–Dawley rats were subjected to MCA occlusion for 90 min by an intraluminal filament. Local CBF was bilaterally recorded by laser Doppler flowmetry. Study I: animals were assigned to one of three treatment arms (n=11 each): (a) vehicle, (b) LF 16-0687 Ms (12.0 mg/kg per day), or (c) LF 16-0687 Ms (36.0 mg/kg per day) given repetitively s.c. over 3 days. The neurological recovery was examined daily. The infarct volume was assessed histologically 7 days after ischemia. Study II: brain swelling and bilateral hemispheric water content were determined at 48 h post ischemia in eight rats, subjected to the low dose regimen as described above, and in eight vehicle-treated control animals. All treated animals showed tendency to exhibit improved neurological recovery throughout the observation period as compared to the vehicle-treated controls, while this improvement was only significant within the low dose group from postischemic days 3 to 4. Low dose LF 16-0687 Ms significantly attenuated the total and cortical infarct volume by 50 and 80%, respectively. Furthermore, postischemic swelling (−62%) and increase in water content of the infarcted brain hemisphere (−60.5%) was significantly inhibited. The present findings provide strong evidence for an involvement of bradykinin-mediated secondary brain damage following from focal cerebral ischemia. Accordingly, specific inhibition of bradykinin B₂ receptors by LF 16-0687 Ms attenuated postischemic brain swelling, improved the functional neurological recovery, and limited ischemic tissue damage, raising its potential for clinical evaluation in patients with acute stroke.     

Novel synthetic analogue of ACTH 4-10 (Semax) but not glycine prevents the enhanced nitric oxide generation in cerebral cortex of rats with incomplete global ischemia

This work investigates whether nitric oxide production and lipid peroxidation contribute to the pathophysiology of ischemia and whether glycine and a novel Russian compound, Semax are neuroprotective via a mechanism involving the regulation nitric oxide (NO) and lipid peroxidation. In brief, nitric oxide and indices of lipid peroxidation were elevated following global ischemia. While glycine proved ineffective in reducing NO levels or ameliorating the neurological deficits following global ischemia, Semax proved to be highly effective in abating the rise in nitric oxide and restoring neurologic functioning.     

Acute administration of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), a selective 5-HT-receptor agonist,causes a biphasic blood pressure response and a bradycardia in the normotensive Sprague-Dawley rat and in the spontaneously hypertensive rat

Summary 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) is a new serotonin (5-HT) receptor agonist that binds selectively to the 5-HT_1A binding site. In the present paper we investigated the cardiovascular effects of 8-OH-DPAT in the normotensive Sprague-Dawley rat and in the spontaneously hypertensive rat. The acute i.v. administration of 8-OH-DPAT (5–150g/kg) was in both rat strains associated with a biphasic blood pressure response and a bradycardia. The initial pressor response was due to a direct vascular effect of 8-OH-DPAT involving activation of-adrenoceptors since it was present in pithed rats and in reserpine pretreated rats and since it was attenuated by prazosin. The longer lasting hypotension was not due to a direct vascular relaxation or a presynaptic inhibition of transmitter release since the hypotension was not evident in pithed rats and since 8-OHDPAT did not influence the pressor responses to electrical stimulation in pithed rats. Rather, the combination of hypotension and bradycardia would suggest a central site of action although the intracerebroventricular (lat. ventricles) route of administration was not more efficient (to induce hypotension) than i.v. administration. At least the bradycardia was mediated by changes in vagal as well as sympathetic discharge since it was prevented by pretreatment with atropine and propranolol in combination but not by pretreatment with either agent alone. The cardiovascular effects of 8-OH-DPAT were not prevented by pretreatment with methergoline, methiothepin, pirenperone or cianserine or by 5-HT depletion by means of p-chlorophenylalanine, which suggests that the putative 5-HT receptor that is responsible for the hypotension and bradycardia to 8-OH-DPAT is not of a presynaptic type and does not have the pharmacological characteristics of a general 5-HT₁ receptor.