Red Blood Cell Microparticles Limit Hematoma Growth in Intracerebral Hemorrhage.

BACKGROUND: Spontaneous intracerebral hemorrhage (sICH) is the deadliest stroke subtype with no effective therapies. Limiting hematoma expansion is a promising therapeutic approach. Red blood cell-derived microparticles (RMPs) are novel hemostatic agents. Therefore, we studied the potential of RMPs in limiting hematoma growth and improving outcomes post-sICH. METHODS: sICH was induced in rats by intrastriatal injection of collagenase. RMPs were prepared from human RBCs by high-pressure extrusion. Behavioral and hematoma/lesion volume assessment were done post-sICH. The optimal dose, dosing regimen, and therapeutic time window of RMP therapy required to limit hematoma growth post-sICH were determined. We also evaluated the effect of RMPs on long-term behavioral and histopathologic outcomes post-sICH. RESULTS: RMP treatment limited hematoma growth following sICH. Hematoma volume (mm3) for vehicle- and RMP- (2.66×1010 particles/kg) treated group was 143±8 and 86±4, respectively. The optimal RMP dosing regimen that limits hematoma expansion was identified. RMPs limit hematoma volume when administered up to 4.5-hour post-sICH. Hematoma volume in the 4.5-hour post-sICH RMP treatment group was lower by 24% when compared with the control group. RMP treatment also improved long-term histopathologic and behavioral outcomes post-sICH. CONCLUSIONS: Our results demonstrate that RMP therapy limits hematoma growth and improves outcomes post-sICH in a rodent model. Therefore, RMPs have the potential to limit hematoma growth in sICH patients.

Red Cell Microparticles Suppress Hematoma Growth Following Intracerebral Hemorrhage in Chronic Nicotine-Exposed Rats.

Spontaneous intracerebral hemorrhage (sICH) is a disabling stroke sub-type, and tobacco use is a prominent risk factor for sICH. We showed that chronic nicotine exposure enhances bleeding post-sICH. Reduction of hematoma growth is a promising effective therapy for sICH in smoking subjects. Red-blood-cell-derived microparticles (RMPs) are hemostatic agents that limit hematoma expansion following sICH in naïve rats. Considering the importance of testing the efficacy of experimental drugs in animal models with a risk factor for a disease, we tested RMP efficacy and the therapeutic time window in limiting hematoma growth post-sICH in rats exposed to nicotine. Young rats were chronically treated with nicotine using osmotic pumps. sICH was induced in rats using an injection of collagenase in the right striatum. Vehicle/RMPs were administered intravenously. Hematoma volume and neurological impairment were quantified ≈24 h after sICH. Hematoma volumes in male and female nicotine-exposed rats that were treated with RMPs at 2 h post-sICH were significantly lower by 26 and 31% when compared to their respective control groups. RMP therapy was able to limit hematoma volume when administered up to 4.5 h post-sICH in animals of both sexes. Therefore, RMPs may limit hematoma growth in sICH patients exposed to tobacco use.

Hyperglycemia / hypoglycemia-induced mitochondrial dysfunction and cerebral ischemic damage in diabetics.

Enhancement of ischemic brain damage is one of the most serious complications of diabetes. Studies from various in vivo and in vitro models of cerebral ischemia have led to an understanding of the role of mitochondria and complex interrelated mitochondrial biochemical pathways leading to the aggravation of ischemic neuronal damage. Advancements in the elucidation of the mechanisms of ischemic brain damage in diabetic subjects have revealed a number of key mitochondrial targets that have been hypothesized to participate in enhancement of brain damage. The present review initially discusses the neurobiology of ischemic neuronal injury, with special emphasis on the central role of mitochondria in mediating its pathogenesis and therapeutic targets. Later it further details the potential role of various biochemical mediators and second messengers causing widespread ischemic brain damage among diabetics via mitochondrial pathways. The present review discusses preclinical data which validates the significance of mitochondrial mechanisms in mediating the aggravation of ischemic cerebral injury in diabetes. Exploitation of these targets may provide effective therapeutic agents for the management of diabetes-related aggravation of ischemic neuronal damage.

Pharmacological modulation of farnesyltransferase subtype I attenuates mecamylamine-precipitated nicotine withdrawal syndrome in mice.

This study was designed to investigate the effect of FTI-276 trifluoroacetate, a selective inhibitor of subtype I, on the development of the mecamylamine-induced nicotine withdrawal syndrome. Mice were administered nicotine (2.5 mg/kg, subcutaneously) four times daily for 7 days. To precipitate nicotine withdrawal, mice were administered one injection of mecamylamine (3 mg/kg, intraperitoneally) 1 h after the last nicotine injection on the test day (day 8). Behavioral observations were made for a period of 30 min immediately after mecamylamine treatment. FTI-276 trifluoroacetate treatment markedly and dose-dependently attenuated the precipitated nicotine withdrawal syndrome, measured by a composite withdrawal severity score, jumping frequency, hyperalgesia in the tail flick test, and anxiety-like behavior in the elevated plus maze test. The results suggest that FTI-276 trifluoroacetate can inhibit the development of a precipitated nicotine withdrawal syndrome, and thus that farnesyltransferase subtype I may be a viable pharmacological target to tackle the problem of nicotine addiction.

Involvement of CCR-2 chemokine receptor activation in ischemic preconditioning and postconditioning of brain in mice.

The present study has been designed to investigate the potential role of CCR-2 chemokine receptor in ischemic preconditioning as well as postconditioning induced reversal of ischemia-reperfusion injury in mouse brain. Bilateral carotid artery occlusion of 17 min followed by reperfusion for 24h was employed in present study to produce ischemia and reperfusion induced cerebral injury in mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was evaluated using elevated plus-maze test and Morris water maze test. Rota rod test was employed to assess motor incoordination. Bilateral carotid artery occlusion followed by reperfusion produced cerebral infarction and impaired memory and motor co-ordination. Three preceding episodes of bilateral carotid artery occlusion for 1 min and reperfusion of 1 min were employed to elicit ischemic preconditioning of brain, while three episodes of bilateral carotid artery occlusion for 10s and reperfusion of 10s immediately after the completion of were employed to elicit ischemic postconditioning of brain. Both prior ischemic preconditioning as well as ischemic postconditioning immediately after global cerebral ischemia prevented markedly ischemia-reperfusion-induced cerebral injury as measured in terms of infarct size, loss of memory and motor coordination. RS 102895, a selective CCR-2 chemokine receptor antagonist, attenuated the neuroprotective effect of both the ischemic preconditioning as well as postconditioning. It is concluded that the neuroprotective effect of both ischemic preconditioning as well as ischemic postconditioning may involve the activation of CCR-2 chemokine receptors.

Potential involvement of tyrosine phosphatase and calpain-related pathways in opioid withdrawal syndrome in mice.

The present study was designed to determine the effect of N'-[6,7-dichloro-4-(4-methoxy-phenyl)-3-oxo-3,4-dihydroquinoxalin-2-yl] hydrazide (SJA 7019), a selective nonpeptide inhibitor of calpain, and sodium orthovanadate, a selective inhibitor of tyrosine phosphatase, on the development of physiological dependence, as assessed by precipitated morphine withdrawal behavior in mice. Subchronic morphine administration (5 mg/kg, intraperitoneally, twice daily for 5 days), followed by a single injection of naloxone was used to precipitate the opioid withdrawal syndrome in mice. Behavioral observations were made immediately after naloxone treatment. Withdrawal syndrome was assessed quantitatively in terms of the withdrawal severity score and the frequency of jumping, rearing, forepaw licking, and circling. Daily single administration of SJA 7019 (1.5, 3, and 6 mg/kg, intraperitoneally) or sodium orthovanadate (5, 10, and 20 mg/kg, intraperitoneally) was continued during the morphine treatment procedure. Administration of SJA 7019 as well as the sodium orthovanadate dose-dependently attenuated the naloxone-induced morphine withdrawal syndrome. Neither SJA 7019 nor sodium orthovanadate significantly affected locomotor activity or morphine-induced antinociception. Therefore, it may be concluded that treatment with SJA 7019 or sodium orthovanadate during the morphine exposure period attenuated the development of physiological dependence on morphine, possibly through mechanisms linked to activation of tyrosine phosphatase and calpain.

SU-6656, a selective Src kinase inhibitor, attenuates mecamylamine-precipitated nicotine withdrawal syndrome in mice.

INTRODUCTION: Src kinase is reported to regulate neuronal nicotinic acetylcholine receptor activity, which is among the principal receptor systems acted upon by nicotine. Src kinase is documented to mediate the pathogenesis of substance dependence. Therefore, the present study has been designed to investigate the effect of SU-6656, selective src kinase inhibitor, on the development of nicotine dependence in a mouse model of mecamylamine-induced nicotine withdrawal syndrome. METHODS: Our experimental protocol consisted of administration of nicotine (2.5 mg/kg, subcutaneously), 4 times daily for 7 days. In order to precipitate nicotine withdrawal, mice were given 1 injection of mecamylamine (3 mg/kg, intraperitoneally), 1 hr after the last nicotine injection on the test day (Day 8). Behavioral observations were made for a period of 30 min immediately after mecamylamine treatment. Withdrawal syndrome was quantitated in terms of a composite withdrawal severity score (WSS), and withdrawal syndrome-related anxiety was assessed by elevated plus maze test results. RESULTS: SU-6656 markedly and dose dependently (p < .01) attenuated mecamylamine-induced experimental nicotine withdrawal syndrome in mice measured in terms of WSS and anxiety score. CONCLUSIONS: Thus, it is suggested that src kinase is involved in the development of nicotine dependence-induced precipitation of its withdrawal syndrome and thus may serve as a viable pharmacological target to tackle the problem of nicotine addiction.

Ischemic brain injury in diabetes and endoplasmic reticulum stress.

Diabetes is a widespread disease characterized by high blood glucose levels due to abnormal insulin activity, production, or both. Chronic diabetes causes many secondary complications including cardiovascular disease: a life-threatening complication. Cerebral ischemia-related mortality, morbidity, and the extent of brain injury are high in diabetes. However, the mechanism of increase in ischemic brain injury during diabetes is not well understood. Multiple mechanisms mediate diabetic hyperglycemia and hypoglycemia-induced increase in ischemic brain injury. Endoplasmic reticulum (ER) stress mediates both brain injury as well as brain protection after ischemia-reperfusion injury. The pathways of ER stress are modulated during diabetes. Free radical generation and mitochondrial dysfunction, two of the prominent mechanisms that mediate diabetic increase in ischemic brain injury, are known to stimulate the pathways of ER stress. Increased ischemic brain injury in diabetes is accompanied by a further increase in the activation of ER stress. As there are many metabolic changes associated with diabetes, differential activation of the pathways of ER stress may mediate pronounced ischemic brain injury in subjects suffering from diabetes. We presently discuss the literature on the significance of ER stress in mediating increased ischemia-reperfusion injury in diabetes.

Chronic Nicotine Exposure Increases Hematoma Expansion following Collagenase-Induced Intracerebral Hemorrhage in Rats.

Spontaneous intracerebral hemorrhage (sICH) is a deadly stroke subtype, and tobacco use increases sICH risk. However epidemiological studies show that, there are no confirmatory studies showing the effect of tobacco use on sICH outcome. Therefore, we evaluated the effect of chronic nicotine exposure (as a surrogate for tobacco use) on outcomes following sICH. Young male and female rats were randomly assigned to either nicotine (4.5 mg/kg b.w. per day) or vehicle (saline) treatment (2-3 weeks) groups. sICH was induced by injecting collagenase into the right striatum. Neurological score and hematoma volume were determined 24 h post-sICH. The hematoma volumes in nicotine-treated male and female rats were significantly higher by 42% and 48% when compared to vehicle-treated male and female rats, respectively. Neurological deficits measured in terms of neurological score for the nicotine-treated male and female groups were significantly higher when compared to the respective vehicle-treated male and female groups. Our results show that chronic nicotine exposure increases hematoma volume post-sICH in rats of both sexes. Identifying the mechanism of nicotine-dependent increase in hematoma growth post-sICH will be crucial to understanding the detrimental effect of tobacco use on the severity of bleeding following intracerebral hemorrhage.

Modulation of src-kinase attenuates naloxone-precipitated opioid withdrawal syndrome in mice.

This study was designed to investigate the effect of 2,3-dihydro-N, N-dimethyl-2-oxo-3-[(4,5,6,7-tetrahydro-1H-indol-2-yl)methylene]-1H-indole-5-sulfonamide (SU-6656), a selective inhibitor of src family kinase, on the development of naloxone-induced opioid withdrawal syndrome in mice. Subacute morphine administration followed by a single injection of naloxone (8 mg/kg, intraperitoneally) was used to precipitate the opioid withdrawal syndrome in mice. Behavioral observations were made immediately after naloxone treatment. The withdrawal syndrome was quantitatively assessed in terms of withdrawal severity score and frequency of jumping, rearing, forepaw licking, and circling. Daily single administration of SU-6656 was continued during the morphine treatment procedure. Injection of naloxone precipitated severe withdrawal in morphine-dependent mice. However, once-daily administration of SU-6656 (1.5, 3, and 6 mg/kg, intraperitoneally) markedly and dose-dependently attenuated the naloxone-induced morphine withdrawal syndrome. Therefore, it seems that an src family-kinase-linked mechanism is involved in the development of physiological opioid dependence; thus, src family kinase may serve as a potential target to address the pathological condition of physiological dependence and abstinence associated with continuous opioid usage.

Tobacco Use: A Major Risk Factor of Intracerebral Hemorrhage.

Spontaneous intracerebral hemorrhage (sICH) is one of the deadliest subtypes of stroke, and no treatment is currently available. One of the major risk factors is tobacco use. In this article, we review literature on how tobacco use affects the risk of sICH and also summarize the known effects of tobacco use on outcomes following sICH. Several studies demonstrate that the risk of sICH is higher in current cigarette smokers compared to non-smokers. The literature also establishes that cigarette smoking not only increases the risk of sICH but also increases hematoma growth, results in worse outcomes, and increases the risk of death from sICH. This review also discusses potential mechanisms activated by tobacco use which result in an increase in risk and severity of sICH. Exploring the underlying mechanisms may help alleviate the risk of sICH in tobacco users as well as may help better manage tobacco user sICH patients.

Automated Assessment of Hematoma Volume of Rodents Subjected to Experimental Intracerebral Hemorrhagic Stroke by Bayes Segmentation Approach.

Simulating a clinical condition of intracerebral hemorrhage (ICH) in animals is key to research on the development and testing of diagnostic or treatment strategies for this high-mortality disease. In order to study the mechanism, pathology, and treatment for hemorrhagic stroke, various animal models have been developed. Measurement of hematoma volume is an important assessment parameter to evaluate post-ICH outcomes. However, due to tissue preservation conditions and variables in digitization, quantification of hematoma volume is usually labor intensive and sometimes even subjective. The objective of this study is to develop an automated method that can accurately and efficiently obtain unbiased cerebral hematoma volume. We developed an application (MATLAB program) that can delineate the brain slice from the background and use the Hue information in the Hue/Saturation/Value (HSV) color space to segment the hematoma region. The segmentation threshold of Hue is calculated based on the Bayes classifier theorem so that the minimum error is mathematically ensured and automated processing is enabled. To validate the developed method, we compared the outcomes from the developed method with the hemoglobin content by the spectrophotometric assay method. The results were linearly correlated with statistical significance. The method was also validated by digital phantoms with an error less than 5% compared with the ground truth from the phantoms. Hematoma volumes yielded by the automated processing and those obtained by the operator's manual operation are highly correlated. This automated segmentation approach can be potentially used to quantify hemorrhagic outcomes in rodent stroke models in an unbiased and efficient way.

Exposure to recurrent hypoglycemia alters hippocampal metabolism in treated streptozotocin-induced diabetic rats.

AIMS: Exposure to recurrent hypoglycemia (RH) is common in diabetic patients receiving glucose-lowering therapies and is implicated in causing cognitive impairments. Despite the significant effect of RH on hippocampal function, the underlying mechanisms are currently unknown. Our goal was to determine the effect of RH exposure on hippocampal metabolism in treated streptozotocin-diabetic rats. METHODS: Hyperglycemia was corrected by insulin pellet implantation. Insulin-treated diabetic (ITD) rats were exposed to mild/moderate RH once a day for 5 consecutive days. RESULTS: The effect of RH on hippocampal metabolism revealed 65 significantly altered metabolites in the RH group compared with controls. Several significant differences in metabolite levels belonging to major pathways (eg, Krebs cycle, gluconeogenesis, and amino acid metabolism) were discovered in RH-exposed ITD rats when compared to a control group. Key glycolytic enzymes including hexokinase, phosphofructokinase, and pyruvate kinase were affected by RH exposure. CONCLUSION: Our results demonstrate that the exposure to RH leads to metabolomics alterations in the hippocampus of insulin-treated streptozotocin-diabetic rats. Understanding how RH affects hippocampal metabolism may help attenuate the adverse effects of RH on hippocampal functions.

Pharmacological inhibition of inducible nitric oxide synthase attenuates the development of seizures in mice.

The present study has been designed to pharmacologically expound the significance of inducible nitric oxide synthase in the pathophysiological progression of seizures using mouse models of chemically induced kindled epilepsy and status epilepticus induced spontaneous recurrent seizures. Pentylenetetrazole (40 mg kg(-1)) (PTZ) administration every second day for a period of 15 days was used to elicit kindled seizure activity in mice. Severity of kindled seizures was assessed in terms of a composite kindled seizure severity score (KSSS). Pilocarpine (100 mg kg(-1)) was injected every 20 min until the onset of status epilepticus. A spontaneous recurrent seizure severity score (SRSSS) was recorded as a measure of quantitative assessment of the progressive development of spontaneous recurrent seizures induced after pilocarpine status epilepticus. Sub-acute PTZ administration induced the development of severe form of kindled seizures in mice. Further, pharmacological status epilepticus elicited a progressive evolution of spontaneous recurrent seizures in the animals. However, treatment of aminoguanidine, a relatively selective inhibitor of inducible nitric oxide synthase, markedly and dose dependently suppressed the development of both PTZ induced kindled seizures as well as pilocarpine induced spontaneous recurrent seizures. Therefore inducible nitric oxide synthase may be implicated in the development of seizures.

Studies on cerebral protection of digoxin against ischemia/reperfusion injury in mice.

The present study was designed to investigate the possible neuroprotective effect of digoxin induced pharmacological preconditioning (PP) and its probable mechanism. Bilateral carotid artery occlusion (BCAO) of 17 min followed by reperfusion for 24 h was employed to produce ischemia and reperfusion (I/R) induced cerebral injury in male swiss albino mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using elevated plus maze test. Degree of motor incoordination was evaluated using inclined beam walking test, rota rod test and lateral push test. Digoxin (0.08 mg/kg, i.p.) was administered 24 h before surgery in a separate group of animals to induce PP. BCAO followed by reperfusion, produced significant rise in cerebral infarct size along with impairment of memory and motor coordination. Digoxin treatment produced a significant decrease in cerebral infarct size and reversal of I/R induced impairment of memory and motor incoordination. Digoxin induced neuroprotective effect was abolished significantly by verapamil (15 mg/kg, i.p.), a L-type calcium channel blocker, ruthenium red (3 mg/kg, s.c.), an intracellular ryanodine receptor blocker and 3,4-dichlorobenzamil (Na(+)/Ca(2+) exchanger inhibitor). These findings indicate that digoxin preconditioning exerts a marked neuroprotective effect on the ischemic brain, which is possibly linked to digitalis induced increase in intracellular calcium levels eventually leading to the activation of calcium sensitive signal transduction cascades.

Blockade of Acid-Sensing Ion Channels Attenuates Recurrent Hypoglycemia-Induced Potentiation of Ischemic Brain Damage in Treated Diabetic Rats.

Diabetes is a chronic metabolic disease and cerebral ischemia is a serious complication of diabetes. Anti-diabetic therapy mitigates this complication but increases the risk of exposure to recurrent hypoglycemia (RH). We showed previously that RH exposure increases ischemic brain damage in insulin-treated diabetic (ITD) rats. The present study evaluated the hypothesis that increased intra-ischemic acidosis in RH-exposed ITD rats leads to pronounced post-ischemic hypoperfusion via activation of acid-sensing (proton-gated) ion channels (ASICs). Streptozotocin-diabetic rats treated with insulin were considered ITD rats. ITD rats were exposed to RH for 5 days and were randomized into Psalmotoxin1 (PcTx1, ASIC1a inhibitor), APETx2 (ASIC3 inhibitor), or vehicle groups. Transient global cerebral ischemia was induced overnight after RH. Cerebral blood flow was measured using laser Doppler flowmetry. Ischemic brain injury in hippocampus was evaluated using histopathology. Post-ischemic hypoperfusion in RH-exposed rats was of greater extent than that in control rats. Inhibition of ASICs prevented RH-induced increase in the extent of post-ischemic hypoperfusion and ischemic brain injury. Since ASIC activation-induced store-operated calcium entry (SOCE) plays a role in vascular tone, next we tested if acidosis activates SOCE via activating ASICs in vascular smooth muscle cells (VSMCs). We observed that SOCE in VSMCs at lower pH is ASIC3 dependent. The results show the role of ASIC in post-ischemic hypoperfusion and increased ischemic damage in RH-exposed ITD rats. Understanding the pathways mediating exacerbated ischemic brain injury in RH-exposed ITD rats may help lower diabetic aggravation of ischemic brain damage.

Preclinical Evaluation of Safety and Biodistribution of Red Cell Microparticles: A Novel Hemostatic Agent.

BACKGROUND: Uncontrollable bleeding is a major cause of mortality and morbidity worldwide. Effective hemostatic agents are urgently needed. Red cell microparticles (RMPs) are a highly promising hemostatic agent. This study evaluated the safety profile of RMPs preliminary to clinical trial. METHODS AND RESULTS: RMPs were prepared from type O+ human red blood cell by high-pressure extrusion. Male rats were treated with RMPs either a 1 × bolus, or 4 × or 20 × administered over 60 minutes. The vehicle-treated group was used as a control. Effects on physiological parameters were evaluated; namely, blood pressure, body and head temperature, hematocrit, and blood gases. We did not observe any adverse effects of RMPs on these physiological parameters. In addition, brain, heart, and lungs of rats treated with 4 × dose (bolus followed by infusion over 60 minutes) or vehicle were examined histologically for signs of thrombosis or other indications of toxicity. No thrombosis or indications of toxicity in brain, heart, or lungs were observed. Studies revealed that RMPs were distributed mainly in liver, spleen, and lymph nodes, and were potentially excreted through the kidneys. CONCLUSIONS: Our study indicates that RMP administration appears not to have any negative impact on the parameters studied and did not produce thrombosis in heart, brain, and lungs. However, more detailed long-term studies confirming the safety of RMP as a hemostatic agent are warranted.

Pharmacological modulation of leukotriene D(4) attenuates the development of opioid dependence in a mouse model of naloxone-induced opioid withdrawal syndrome.

The present study was designed to investigate the effect of montelukast sodium, a leukotriene D(4) receptor antagonist, and 1,2,3,4,tetrahydroisoquinoline, a leukotriene D(4) synthetic pathway inhibitor, on the development of morphine dependence in a mouse model of naloxone-induced opioid withdrawal syndrome. Morphine (5 mg/kg, i.p.) was administered twice daily for a period of 5 days following which a single injection of naloxone (8 mg/kg, i.p.) precipitated the opioid withdrawal syndrome in mice. Behavioral observations were made for a period of 30 min immediately after naloxone treatment. The withdrawal syndrome was quantitatively assessed in terms of withdrawal severity score and the frequency of jumping, rearing, fore paw licking and circling. Montelukast sodium as well as 1,2,3,4,tetrahydroisoquinoline, markedly and dose dependently (p<0.01) attenuated the morphine-naloxone-induced opioid withdrawal syndrome in mice. However, administration of montelukast sodium or 1,2,3,4,tetrahydroisoquinoline did not alter the activity of the central nervous system, assessed in terms of locomotor activity count thus ruling out any per se sedative action of montelukast sodium. Further, pretreatment with montelukast sodium or 1,2,3,4,tetrahydroisoquinoline did not alter the acute analgesic effect of morphine. Thus, leukotriene D(4) may be involved in the development of opioid dependence and the precipitation of its withdrawal syndrome and thus may serve as a viable pharmacological target to tackle the problem of opioid addiction.

Pharmacological preconditioning of the brain: a possible interplay between opioid and calcitonin gene related peptide transduction systems.

The present study has been undertaken to investigate the possible link between calcitonin gene related peptide (CGRP) and opioid receptor transduction systems in the neuroprotective mechanism of pharmacological preconditioning. Occlusion of the bilateral carotid artery for 17 min, followed by reperfusion for 24 h, was employed to produce ischemia and reperfusion (I/R) induced cerebral injury in mice. Cerebral infarct size was measured by using triphenyltetrazolium chloride staining. Memory was assessed using the Morris water maze (MWM) test. Degree of motor incoordination was evaluated using the inclined beam walk test, rota-rod test, and lateral push test. Morphine (8 mg/kg, ip), an opioid agonist, and capsaicin (0.1 mg/kg, iv), a CGRP releasing agent, were administered 24 h before surgery to separate groups of animals to induce pharmacological preconditioning. Bilateral carotid artery occlusion, followed by reperfusion, produced a significant increase in the cerebral infarct size and impaired memory as well as motor coordination. Morphine and capsaicin treatment produced both a significant decrease in the cerebral infarct size and a reversal of I/R-induced impairment of memory and motor-coordination. Morphine-induced (8 mg/kg, ip) neuroprotective effects were completely decreased by sumatriptan (8 mg/kg, ip, a CGRPrelease inhibitor) administered 1 h before and 6 h and 12 h after morphine administration. Capsaicin-induced neuroprotection was decreased by naloxone (5 mg/kg, ip, an opioid antagonist) administered 1 h before and 6 h and 12 h after capsaicin administration. These findings indicate that the transduction systems mediating morphine- and capsaicin-induced pharmacological preconditioning in brain are possibly interlinked with one another.