Derangements of post-ischemic cerebral blood flow by protein kinase C delta

PRMT7 can prevent neurovascular uncoupling, blood-brain barrier permeability, and mitochondrial dysfunction in repetitive and mild traumatic brain injury

Mild traumatic brain injury (TBI) comprises the largest percentage of TBI-related injuries, with pathophysiological and functional deficits that persist in a subset of TBI patients. In our three-hit paradigm of repetitive and mild traumatic brain injury (rmTBI), we observed neurovascular uncoupling via decreased red blood cell velocity, microvessel diameter, and leukocyte rolling velocity 3 days post-rmTBI via intra-vital two-photon laser scanning microscopy. Furthermore, our data suggest increased blood-brain barrier (BBB) permeability (leakage), with corresponding decrease in junctional protein expression post-rmTBI. Mitochondrial oxygen consumption rates (measured via Seahorse XFe24) were also altered 3 days post-rmTBI, along with disrupted mitochondrial dynamics of fission and fusion. Overall, these pathophysiological findings correlated with decreased protein arginine methyltransferase 7 (PRMT7) protein levels and activity post-rmTBI. Here, we increased PRMT7 levels in vivo to assess the role of the neurovasculature and mitochondria post-rmTBI. In vivo overexpression of PRMT7 using a neuronal specific AAV vector led to restoration of neurovascular coupling, prevented BBB leakage, and promoted mitochondrial respiration, altogether to suggest a protective and functional role of PRMT7 in rmTBI.

Activation of Neuropeptide Y2 Receptor Can Inhibit Global Cerebral Ischemia-Induced Brain Injury

Cardiopulmonary arrest (CA) can greatly impact a patient's life, causing long-term disability and death. Although multi-faceted treatment strategies against CA have improved survival rates, the prognosis of CA remains poor. We previously reported asphyxial cardiac arrest (ACA) can cause excessive activation of the sympathetic nervous system (SNS) in the brain, which contributes to cerebral blood flow (CBF) derangements such as hypoperfusion and, consequently, neurological deficits. Here, we report excessive activation of the SNS can cause enhanced neuropeptide Y levels. In fact, mRNA and protein levels of neuropeptide Y (NPY, a 36-amino acid neuropeptide) in the hippocampus were elevated after ACA-induced SNS activation, resulting in a reduced blood supply to the brain. Post-treatment with peptide YY_3-36 (PYY_3-36), a pre-synaptic NPY2 receptor agonist, after ACA inhibited NPY release and restored brain circulation. Moreover, PYY_3-36 decreased neuroinflammatory cytokines, alleviated mitochondrial dysfunction, and improved neuronal survival and neurological outcomes. Overall, NPY is detrimental during/after ACA, but attenuation of NPY release via PYY_3-36 affords neuroprotection. The consequences of PYY_3-36 inhibit ACA-induced 1) hypoperfusion, 2) neuroinflammation, 3) mitochondrial dysfunction, 4) neuronal cell death, and 5) neurological deficits. The present study provides novel insights to further our understanding of NPY's role in ischemic brain injury.

Palmitic acid methyl ester inhibits cardiac arrest-induced neuroinflammation and mitochondrial dysfunction

We previously discovered that palmitic acid methyl ester (PAME) is a potent vasodilator released from the sympathetic ganglion with vasoactive properties. Post-treatment with PAME can enhance cortical cerebral blood flow and functional learning and memory, while inhibiting neuronal cell death in the CA1 region of the hippocampus under pathological conditions (i.e. cerebral ischemia). Since mechanisms underlying PAME-mediated neuroprotection remain unclear, we investigated the possible neuroprotective mechanisms of PAME after 6 min of asphyxial cardiac arrest (ACA, an animal model of global cerebral ischemia). Our results from capillary-based immunoassay (for the detection of proteins) and cytokine array suggest that PAME (0.02 mg/kg) can decrease neuroinflammatory markers, such as ionized calcium binding adaptor molecule 1 (Iba1, a specific marker for microglia/macrophage activation) and inflammatory cytokines after cardiopulmonary resuscitation. Additionally, the mitochondrial oxygen consumption rate (OCR) and respiratory function in the hippocampal slices were restored following ACA (via Seahorse XF24 Extracellular Flux Analyzer) suggesting that PAME can ameliorate mitochondrial dysfunction. Finally, hippocampal protein arginine methyltransferase 1 (PRMT1) and PRMT8 are enhanced in the presence of PAME to suggest a possible pathway of methylated fatty acids to modulate arginine-based enzymatic methylation. Altogether, our findings suggest that PAME can provide neuroprotection in the presence of ACA to alleviate neuroinflammation and ameliorate mitochondrial dysfunction.

The Combination of Astragalus membranaceus and Ligustrazine Protects Against Thrombolysis-Induced Hemorrhagic Transformation Through PKCδ/Marcks Pathway in Cerebral Ischemia Rats

Astragalus membranaceus (Ast) and ligustrazine (Lig) have a protective effect on lower hemorrhagic transformation induced by pharmaceutical thrombolysis. The cerebral ischemia rat model was induced with autologous blood clot injections. A combination of Ast and Lig, or a protein kinase C delta (PKCδ) inhibitor—rottlerin, or a combination of Ast, Lig, and rottlerin was administered immediately after recombinant tissue plasminogen activator injection. The cerebral infarct area, neurological deficits, cerebral hemorrhage status, neuronal damage and tight junctions’ changes in cerebral vessels, and the messenger RNA and protein levels of PKCδ, myristoylated alanine-rich C kinase substrate (Marcks), and matrix metallopeptidase 9 (MMP9) were determined after 3 h and 24 h of thrombolysis. The ultrastructure of the neuronal damage and tight junctions was examined under a transmission electron microscope. The expression levels of PKCδ, Marcks, and MMP9 were assessed by immunohistochemistry, western blot, and quantitative real-time polymerase chain reaction . Administration of Ast and Lig not only significantly decreased neurological deficit scores, infarct volumes, and cerebral hemorrhage but also inhibited the disruption due to neuronal dysfunction and the tight junction integrity in the cerebral vessel. Treatment with a combination of Ast and Lig effectively protected ischemia-induced microhemorrhage transformation through PKCδ/Marcks pathway suppression.

Palmitic acid methyl ester is a novel neuroprotective agent against cardiac arrest

We previously discovered that palmitic acid methyl ester (PAME) is a potent vasodilator first identified and released from the superior cervical ganglion and remain understudied. Thus, we investigated PAME's role in modulating cerebral blood flow (CBF) and neuroprotection after 6 min of cardiac arrest (model of global cerebral ischemia). Our results suggest that PAME can enhance CBF under normal physiological conditions, while administration of PAME (0.02 mg/kg) immediately after cardiopulmonary resuscitation can also enhance CBF in vivo. Additionally, functional learning and spatial memory assessments (via T-maze) 3 days after asphyxial cardiac arrest (ACA) suggest that PAME-treated rats have improved learning and memory recovery versus ACA alone. Furthermore, improved neuronal survival in the CA1 region of the hippocampus were observed in PAME-treated, ACA-induced rats. Altogether, our findings suggest that PAME can enhance CBF, alleviate neuronal cell death, and promote functional outcomes in the presence of ACA.

Age-Dependent Levels of Protein Kinase Cs in Brain: Reduction of Endogenous Mechanisms of Neuroprotection

Neurodegenerative diseases are among the leading causes of mortality and disability worldwide. However, current therapeutic approaches have failed to reach significant results in their prevention and cure. Protein Kinase Cs (PKCs) are kinases involved in the pathophysiology of neurodegenerative diseases, such as Alzheimer's Disease (AD) and cerebral ischemia. Specifically ε, δ, and γPKC are associated with the endogenous mechanism of protection referred to as ischemic preconditioning (IPC). Existing modulators of PKCs, in particular of εPKC, such as ψεReceptor for Activated C-Kinase (ψεRACK) and Resveratrol, have been proposed as a potential therapeutic strategy for cerebrovascular and cognitive diseases. PKCs change in expression during aging, which likely suggests their association with IPC-induced reduction against ischemia and increase of neuronal loss occurring in senescent brain. This review describes the link between PKCs and cerebrovascular and cognitive disorders, and proposes PKCs modulators as innovative candidates for their treatment. We report original data showing εPKC reduction in levels and activity in the hippocampus of old compared to young rats and a reduction in the levels of δPKC and γPKC in old hippocampus, without a change in their activity. These data, integrated with other findings discussed in this review, demonstrate that PKCs modulators may have potential to restore age-related reduction of endogenous mechanisms of protection against neurodegeneration.

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.

Utilizing the Modified T-Maze to Assess Functional Memory Outcomes After Cardiac Arrest

BACKGROUND

Evaluating mild to moderate cognitive impairment in a global cerebral ischemia (i.e. cardiac arrest) model can be difficult due to poor locomotion after surgery. For example, rats who undergo surgical procedures and are subjected to the Morris water maze may not be able to swim, thus voiding the experiment. New Method: We established a modified behavioral spontaneous alternation T-maze test. The major advantage of the modified T-maze protocol is its relatively simple design that is powerful enough to assess functional learning/memory after ischemia. Additionally, the data analysis is simple and straightforward. We used the T-maze to determine the rats' learning/memory deficits both in the presence or absence of mild to moderate (6 min) asphyxial cardiac arrest (ACA). Rats have a natural tendency for exploration and will explore the alternate arms in the T-maze, whereas hippocampal-lesioned rats tend to adopt a side-preference resulting in decreased spontaneous alternation ratios, revealing the hippocampal-related functional learning/memory in the presence or absence of ACA.

RESULTS

ACA groups have higher side-preference ratios and lower alternations as compared to control. Comparison with Existing Method(s): The Morris water and Barnes maze are more prominent for assessing learning/memory function. However, the Morris water maze is more stressful than other mazes. The Barnes maze is widely used to measure reference (long-term) memory, while ACA-induced neurocognitive deficits are more closely related to working (short-term) memory.

CONCLUSIONS

We have developed a simple, yet effective strategy to delineate working (short-term) memory via the T-maze in our global cerebral ischemia model (ACA).

Emulsified isoflurane postconditioning improves survival and neurological outcomes in a rat model of cardiac arrest

Emulsified isoflurane (EIso) has a protective effect against ischemia/reperfusion (I/R) injury in animal models. However, the protective effects of EIso on global cerebral I/R injury remain unclear. The present study aimed to investigate whether EIso postconditioning was able to improve survival and neurological outcomes in a rat model of cardiac arrest (CA). Rats were randomly divided into five groups, namely the control, EIso-2ml, EIso-4ml, isoflurane (Iso) and emulsion (E) groups. All rats were resuscitated by a standardized method following 6 min of asphyxia. Furthermore, all interventions were administered immediately following the return of spontaneous circulation (ROSC). The animal survival was recorded daily, and evaluations of behavioral and brain morphology were assessed at 1 and 7 days after ROSC. The results showed that EIso treatment increased the survival rate 7 days after ROSC, with a 41.7% 7-day survival in the EIso-2ml group, 66.7% in the EIso-4ml group and 50% in the Iso group compared with 33.3% survival in the control and E groups. Moreover, the neural deficit score and memory function were improved in the EIso-4ml group, and this treatment also ameliorated brain hippocampal cell injury and apoptosis. In addition, a better brain protective effect was observed in the EIso-4ml group compared with the EIso-2ml, Iso and E groups. In summary, the data of the present study suggest that EIso postconditioning improved the survival and neurological outcomes following CA in a dose-dependent manner.

Interruption of perivascular sympathetic nerves of cerebral arteries offers neuroprotection against ischemia

Sympathetic nervous system activity is increased after cardiopulmonary arrest, resulting in vasoconstrictor release from the perivascular sympathetic nerves of cerebral arteries. However, the pathophysiological function of the perivascular sympathetic nerves in the ischemic brain remains unclear. A rat model of global cerebral ischemia (asphyxial cardiac arrest, ACA) was used to investigate perivascular sympathetic nerves of cerebral arteries via bilateral decentralization (preganglionic lesion) of the superior cervical ganglion (SCG). Decentralization of the SCG 5 days before ACA alleviated hypoperfusion and afforded hippocampal neuroprotection and improved functional outcomes. These studies can provide further insights into the functional mechanism(s) of the sympathetic nervous system during ischemia.

NEW & NOTEWORTHY

Interruption of the perivascular sympathetic nerves can alleviate CA-induced hypoperfusion and neuronal cell death in the CA1 region of the hippocampus to enhance functional learning and memory.

Opening the window: Ischemic postconditioning reduces the hyperemic response of delayed tissue plasminogen activator and extends its therapeutic time window in an embolic stroke model

It has been reported that ischemic postconditioning (PC) changes the reperfusion pattern in permanent or transient models of stroke and confers neuroprotection. However, the effects of PC and subsequent use of tissue plasminogen activator (tPA) for the treatment of embolic stroke have not yet been investigated. Rats were subjected to stroke by injection of a preformed clot into the middle cerebral artery and randomly assigned to vehicle (saline 0.1 ml/100 g), tPA (3 mg/kg), PC only or PC+tPA (3 mg/kg). tPA was injected at 6 h after embolic stroke and PC was conducted at 6.5 h after ischemia by using five cycles of a 10 s occlusion and 30 s of reopening of the bilateral common carotid arteries. Cerebral blood flow (CBF) was monitored for 60 min from the time of tPA injection. Infarct size, blood brain barrier disruption, edema, neurological deficits, reactive oxygen species and apoptosis were measured 2 days later. PC decreased infarct volume, but PC+tPA was more neuroprotective than PC alone. While tPA alone dramatically increased CBF, conducting PC caused a gradual increase in CBF. A combination of PC+tPA reduced BBB leakage, brain edema, apoptosis and reactive oxygen species levels. Furthermore, a combination of PC+tPA improved neurological functions at 48 h after the induced stroke. In conclusion, PC hampered malignant hyperemia after reperfusion with tPA and extended its therapeutic window up to 6 h. Compared to PC alone, combination of thrombolysis and PC showed a better neuroprotection.

Protein kinase Cδ mediates histamine-evoked itch and responses in pruriceptors

Background

Itch-producing compounds stimulate receptors expressed on small diameter fibers that innervate the skin. Many of the currently known pruritogen receptors are G_q Protein-Coupled Receptors (G_qPCR), which activate Protein Kinase C (PKC). Specific isoforms of PKC have been previously shown to perform selective functions; however, the roles of PKC isoforms in regulating itch remain unclear. In this study, we investigated the novel PKC isoform PKCδ as an intracellular modulator of itch signaling in response to histamine and the non-histaminergic pruritogens chloroquine and β-alanine.

Results

Behavioral experiments indicate that PKCδ knock-out (KO) mice have a 40% reduction in histamine-induced scratching when compared to their wild type littermates. On the other hand, there were no differences between the two groups in scratching induced by the MRGPR agonists chloroquine or β-alanine. PKCδ was present in small diameter dorsal root ganglion (DRG) neurons. Of PKCδ-expressing neurons, 55% also stained for the non-peptidergic marker IB4, while a smaller percentage (15%) expressed the peptidergic marker CGRP. Twenty-nine percent of PKCδ-expressing neurons also expressed TRPV1. Calcium imaging studies of acutely dissociated DRG neurons from PKCδ-KO mice show a 40% reduction in the total number of neurons responsive to histamine. In contrast, there was no difference in the number of capsaicin-responsive neurons between KO and WT animals. Acute pharmacological inhibition of PKCδ with an isoform-specific peptide inhibitor (δV1-1) also significantly reduced the number of histamine-responsive sensory neurons.

Conclusions

Our findings indicate that PKCδ plays a role in mediating histamine-induced itch, but may be dispensable for chloroquine- and β-alanine-induced itch.

Global and regional differences in cerebral blood flow after asphyxial versus ventricular fibrillation cardiac arrest in rats using ASL-MRI

Both ventricular fibrillation cardiac arrest (VFCA) and asphyxial cardiac arrest (ACA) are frequent causes of CA. However, only isolated reports compared cerebral blood flow (CBF) reperfusion patterns after different types of CA, and even fewer reports used methods that allow serial and regional assessment of CBF. We hypothesized that the reperfusion patterns of CBF will differ between individual types of experimental CA. In a prospective block-randomized study, fentanyl-anesthetized adult rats were subjected to 8min VFCA or ACA. Rats were then resuscitated with epinephrine, bicarbonate, manual chest compressions and mechanical ventilation. After the return of spontaneous circulation, CBF was then serially assessed via arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cortex, thalamus, hippocampus and amygdala/piriform complex over 1h resuscitation time (RT). Both ACA and VFCA produced significant temporal and regional differences in CBF. All regions in both models showed significant changes over time (p<0.01), with early hyperperfusion and delayed hypoperfusion. ACA resulted in early hyperperfusion in cortex and thalamus (both p<0.05 vs. amygdala/piriform complex). In contrast, VFCA induced early hyperperfusion only in cortex (p<0.05 vs. other regions). Hyperperfusion was prolonged after ACA, peaking at 7min RT (RT7; 199% vs. BL, Baseline, in cortex and 201% in thalamus, p<0.05), then returning close to BL at ∼RT15. In contrast, VFCA model induced mild hyperemia, peaking at RT7 (141% vs. BL in cortex). Both ACA and VFCA showed delayed hypoperfusion (ACA, ∼30% below BL in hippocampus and amygdala/piriform complex, p<0.05; VFCA, 34-41% below BL in hippocampus and amygdala/piriform complex, p<0.05). In conclusion, both ACA and VFCA in adult rats produced significant regional and temporal differences in CBF. In ACA, hyperperfusion was most pronounced in cortex and thalamus. In VFCA, the changes were more modest, with hyperperfusion seen only in cortex. Both insults resulted in delayed hypoperfusion in all regions. Both early hyperperfusion and delayed hypoperfusion may be important therapeutic targets. This study was approved by the University of Pittsburgh IACUC 1008816-1.

Protein kinase C delta modulates endothelial nitric oxide synthase after cardiac arrest

We previously showed that inhibition of protein kinase C delta (PKCδ) improves brain perfusion 24 hours after asphyxial cardiac arrest (ACA) and confers neuroprotection in the cortex and CA1 region of the hippocampus 7 days after arrest. Therefore, in this study, we investigate the mechanism of action of PKCδ-mediated hypoperfusion after ACA in the rat by using the two-photon laser scanning microscopy (TPLSM) to observe cortical cerebral blood flow (CBF) and laser Doppler flowmetry (LDF) detecting regional CBF in the presence/absence of δV1-1 (specific PKCδ inhibitor), nitric oxide synthase (NOS) substrate (L-arginine, L-arg) and inhibitor (N(ω)-Nitro-L-arginine, NLA), and nitric oxide (NO) donor (sodium nitroprusside, SNP). There was an increase in regional LDF and local (TPLSM) CBF in the presence of δV1-1+L-arg, but only an increase in regional CBF under δV1-1+SNP treatments. Systemic blood nitrite levels were measured 15 minutes and 24 hours after ACA. Nitrite levels were enhanced by pretreatment with δV1-1 30 minutes before ACA possibly attributable to enhanced endothelial NOS protein levels. Our results suggest that PKCδ can modulate NO machinery in cerebral vasculature. Protein kinase C delta can depress endothelial NOS blunting CBF resulting in hypoperfusion, but can be reversed with δV1-1 improving brain perfusion, thus providing subsequent neuroprotection after ACA.

Fatty acid methyl esters and Solutol HS 15 confer neuroprotection after focal and global cerebral ischemia

We previously showed that palmitic acid methyl ester (PAME) and stearic acid methyl ester (SAME) are simultaneously released from the sympathetic ganglion and PAME possesses potent vasodilatory properties which may be important in cerebral ischemia. Since PAME is a potent vasodilator simultaneously released with SAME, our hypothesis was that PAME/SAME confers neuroprotection in rat models of focal/global cerebral ischemia. We also examined the neuroprotective properties of Solutol HS15, a clinically approved excipient because it possesses similar fatty acid compositions as PAME/SAME. Asphyxial cardiac arrest (ACA, 6 min) was performed 30 min after PAME/SAME treatment (0.02 mg/kg, IV). Solutol HS15 (2 ml/kg, IP) was injected chronically for 14 days (once daily). Histopathology of hippocampal CA1 neurons was assessed 7 days after ACA. For focal ischemia experiments, PAME, SAME, or Solutol HS15 was administered following reperfusion after 2 h of middle cerebral artery occlusion (MCAO). 2,3,5-Triphenyltetrazolium staining of the brain was performed 24 h after MCAO and the infarct volume was quantified. Following ACA, the number of surviving hippocampal neurons was enhanced by PAME-treated (68%), SAME-treated (69%), and Solutol-treated HS15 (68%) rats as compared to ACA only-treated groups. Infarct volume was decreased by PAME (83%), SAME (68%), and Solutol HS15 (78%) as compared to saline (vehicle) in MCAO-treated animals. PAME, SAME, and Solutol HS15 provide robust neuroprotection in both paradigms of ischemia. This may prove therapeutically beneficial since Solutol HS15 is already administered as a solublizing agent to patients. With proper timing and dosage, administration of Solutol HS15 and PAME/SAME can be an effective therapy against cerebral ischemia.

Genetics and genomics of ischemic tolerance: focus on cardiac and cerebral ischemic preconditioning

A subthreshold ischemic insult applied to an organ such as the heart and/or brain may help to reduce damage caused by subsequent ischemic episodes. This phenomenon is known as ischemic tolerance mediated by ischemic preconditioning (IPC) and represents the most powerful endogenous mechanism against ischemic injury. Various molecular pathways have been implicated in IPC, and several compounds have been proposed as activators or mediators of IPC. Recently, it has been established that the protective phenotype in response to ischemia depends on a coordinated response at the genomic, molecular, cellular and tissue levels by introducing the concept of 'genomic reprogramming' following IPC. In this article, we sought to review the genetic expression profiles found in cardiac and cerebral IPC studies, describe the differences between young and aged organs in IPC-mediated protection, and discuss the potential therapeutic application of IPC and pharmacological preconditioning based on the genomic response.

Differential effects of delta and epsilon protein kinase C in modulation of postischemic cerebral blood flow

Cerebral ischemia causes cerebral blood flow (CBF) derangements resulting in neuronal damage by enhanced protein kinase C delta (δPKC) levels leading to hippocampal and cortical neuronal death after ischemia. Contrarily, activation of εPKC mediates ischemic tolerance by decreasing vascular tone providing neuroprotection. However, whether part of this protection is due to the role of differential isozymes of PKCs on CBF following cerebral ischemia remains poorly understood. Rats pretreated with a δPKC specific inhibitor (δV1-1, 0.5 mg/kg) exhibited attenuation of hyperemia and latent hypoperfusion characterized by vasoconstriction followed by vasodilation of microvessels after two-vessel occlusion plus hypotension. In an asphyxial cardiac arrest (ACA) model, rats treated with δ V1-1 (pre- and postischemia) exhibited improved perfusion after 24 h and less hippocampal CA1 and cortical neuronal death 7 days after ACA. On the contrary, εPKC-selective peptide activator, conferred neuroprotection in the CA1 region of the rat hippocampus 30 min before induction of global cerebral ischemia and decreased regional CBF during the reperfusion phase. These opposing effects of δ v. εPKC suggest a possible therapeutic potential by modulating CBF preventing neuronal damage after cerebral ischemia.