Cannabidiol in experimental cerebral ischemia.

The absence of blood flow in cerebral ischemic conditions triggers a multitude of intricate pathophysiological mechanisms, including excitotoxicity, oxidative stress, neuroinflammation, disruption of the blood-brain barrier and white matter disarrangement. Despite numerous experimental studies conducted in preclinical settings, existing treatments for cerebral ischemia (CI), such as mechanical and pharmacological therapies, remain constrained and often entail significant side effects. Therefore, there is an imperative to explore innovative strategies for addressing CI outcomes. Cannabidiol (CBD), the most abundant non-psychotomimetic compound derived from Cannabis sativa, is a pleiotropic substance that interacts with diverse molecular targets and has the potential to influence various pathophysiological processes, thereby contributing to enhanced outcomes in CI. This chapter provides a comprehensive overview of the primary effects of CBD in in vitro and diverse animal models of CI and delves into some of its plausible mechanisms of neuroprotection.

Blood-Brain Barrier Rescue by Roflumilast After Transient Global Cerebral Ischemia in Rats.

Phosphodiesterase 4 inhibitors (PDE4-I), which selectively increase cyclic adenosine monophosphate (cAMP) levels, have shown neuroprotective effects after several neurological injuries inducing blood-brain barrier (BBB) damage including local/focal cerebral ischemia. The present investigated whether roflumilast confers BBB neuroprotection in the hippocampus after transient global cerebral ischemia (TGCI) in rats. TGCI resulted in whole BBB disruption as measured by the increase of Evans blue (EB) and IgG extravasation, neurodegeneration, and downregulation of claudin-5 and endothelial nitric oxide synthase (eNOS) levels in the CA1 hippocampal subfield of ischemic rats. Roflumilast attenuated BBB disruption and restored the levels of eNOS in the CA1 hippocampal area. Moreover, roflumilast increased the levels of B2 cell lymphoma (BcL-2) and neuron-glial antigen-2 (NG2) in the CA1 subfield after global ischemia in rats. The protective effects of roflumilast against TGCI-induced BBB breakdown might involve preservation of BBB integrity, vascularization and angiogenesis, and myelin repair.

NLX-101, a 5-HT1A receptor-biased agonist, improves pattern separation and stimulates neuroplasticity in aged rats.

5-HT1A serotonin receptors may play a role in cognitive function changes related to advanced age. Here, we investigated the effects of acute and repeated treatment with NLX-101 (F15599), a postsynaptic 5-HT1A receptor-biased agonist, and F13714, a presynaptic 5-HT1A receptor-biased agonist on spatial object pattern separation (OPS) in aged (22-24 months) rats. Neuroplasticity markers including brain-derived neurotrophic factor, PSD95, synaptophysin, and doublecortin were evaluated in the hippocampus. Unlike younger rats, aged rats were incapable of discriminating any new position of the objects in the arena, reflecting the detrimental effect of aging on pattern separation. However, aged animals treated with NLX-101 showed a significant cognitive improvement in the OPS test, accompanied by increases in hippocampal brain-derived neurotrophic factor and PSD95 protein levels. In contrast, no improvement in OPS performance was observed when aged rats received F13714. Both F13714 and NLX-101 increased the number of newborn neurons in the hippocampi of aged rats. These findings provide a rationale for targeting post-synaptic 5-HT1A as a treatment for cognitive deficits related to aging.

Delayed administration of Trichilia catigua A. Juss. Ethyl-acetate fraction after cerebral ischemia prevents spatial memory deficits, decreases oxidative stress, and impacts neural plasticity in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Trichilia catigua A. Juss (Meliaceae) is used in Brazilian folk medicine to alleviate fatigue and emotional stress and improve memory. Previous studies from our laboratory reported that an ethyl-acetate fraction (EAF) of T. catigua that was given before cerebral ischemia in vivo prevented memory loss and reduced oxidative stress and neuroinflammation. Despite the value of these findings of a neuroprotective effect of T. catigua, treatment that was given immediately before or immediately after ischemia limits its clinical relevance. Thus, unknown is whether T. catigua possesses a specific time window of efficacy (TWE) when administered postischemia. AIM OF THE STUDY: Given continuity to previous studies, we investigated whether an EAF of T. catigua maintains its neuroprotective properties if treatment begins at different time windows of efficacy after ischemia. We also evaluated, for the first time, whether T. catigua possesses neuroplasticity/neurotrophic properties. MATERIAL AND METHODS: Rats were subjected to transient global brain ischemia (TGCI) and then given a single dose of the EAF (400 mg/kg) or vehicle (1 ml/kg) orally 1, 4, or 6 h postischemia. The levels of protein PCG, GSH, and GSSG, and activity of SOD and CAT were assayed as markers of oxidative stress on the day after ischemia. In another experiment, naive rats underwent spatial learning training in a radial maze task and then subjected to TGCI. Delayed treatment with the EAF began 4 or 6 h later and continued for 7 days. Retrograde memory performance was assessed 10, 17, and 24 days postischemia. Afterward, brains were examined for neurodegeneration and neuronal dendritic morphology in the hippocampus and cerebral cortex. Another group received the EAF at 4 h of reperfusion, and 4 days later their brains were examined for GFAP and Iba-1 immunoreactivity. Lastly, ischemic rats received the EAF 4 h after ischemia and neural plasticity-related proteins, BDNF, SYN, PSD 95, and NeuN were measured in the hippocampus 7 and 14 days after ischemia. RESULTS: A single EAF administration 1, 4, or 6 h postischemia alleviated oxidative stress that was caused by ischemia, expressed as a reduction of the amount of the PCG and GSSG, normalization of the GSH/GSSG ratio, and the restoration of SOD activity. Ischemia caused the persistent loss of memory (i.e., amnesia), an outcome that was consistently ameliorated by treatment with the EAF that was initiated 4 or 6 h postischemia. The 4 h delay in EAF treatment positively impacted dendritic morphology in neurons that survived ischemia. TGCI reduced BDNF, SYN, PSD-95, and NeuN protein levels in the hippocampus and cerebral cortex. The EAF normalized SYN and PSD-95 protein levels. Ischemia-induced neurodegeneration and glial cell activation were not prevented by EAF treatment. CONCLUSION: The present study corroborates prior data that demonstrated the neuroprotective potential of T. catigua and extends these data by showing that the delayed administration of EAF postischemia effectively prevented memory impairment and decreased oxidative stress, dendritic deterioration, and synaptic protein loss within a TWE that ranged from 1 to 6 h. This specific TWE in preclinical research may have clinical relevance by suggesting the possible utility of this plant for the development of neuroprotective strategies in the setting of ischemic brain diseases. Another innovative finding of the present study was the possible neurotrophic/neuroplastic properties of T. catigua.

Long-term treatment with roflumilast improves learning of fear extinction memory and anxiety-like response in a type-1 diabetes mellitus animal model.

Diabetic encephalopathy is related to serious damage to the Central Nervous System leading to several disturbances in memory processing and emotions. It is known that the cyclic adenosine 3',5'-monophosphate (cAMP) responsive element-binding protein (CREB) pathway participates in neuronal plasticity and prevention of neuroinflammation, as well as the mediation of learning/memory processes and emotions in brain areas such as the hippocampus (HIP) and prefrontal cortex (PFC). We aimed to investigate the effect of acute (one injection) and long-term treatment (21 days) with roflumilast (ROF; i.p.; 0, 0.01, 0.03, 0.1 mg/kg), a drug able to inhibit the enzyme phosphodiesterase-4 (PDE-4) responsible for cAMP hydrolysis, on parameters related to the acquisition of fear extinction memory and anxiety-like responses in animals with type-1 diabetes mellitus (T1DM) induced through one injection of streptozotocin (60 mg/kg; ip; STZ animals). When we performed acute treatment, no difference was observed between all the groups when resubmitted to the same context paired with an aversive stimulus (footshock) or to a neutral context. In contrast, long-term treatment was able to improve learning of extinction fear memory and discriminating between a conditioned and neutral context. Moreover, this treatment decreased the pronounced anxiety-like response of STZ animals. In addition, there was an increase in the product of the CREB signaling pathway, the pro brain-derived neurotrophic factor, in the HIP and PFC of these animals. The treatment did not impair glycemic control, whereas it decreased the animal's blood glucose levels. To conclude, these findings suggest that ROF treatment repositioning has potential for future translational investigations involving diabetic patients considering its beneficial effects on emotional processes related to fear memory and anxiety, in addition to improvement of glycemic control.

Cannabidiol Exerts a Neuroprotective and Glia-Balancing Effect in the Subacute Phase of Stroke.

Pharmacological agents limiting secondary tissue loss and improving functional outcomes after stroke are still limited. Cannabidiol (CBD), the major non-psychoactive component of Cannabis sativa, has been proposed as a neuroprotective agent against experimental cerebral ischemia. The effects of CBD mostly relate to the modulation of neuroinflammation, including glial activation. To investigate the effects of CBD on glial cells after focal ischemia in vivo, we performed time-lapse imaging of microglia and astroglial Ca2+ signaling in the somatosensory cortex in the subacute phase of stroke by in vivo two-photon laser-scanning microscopy using transgenic mice with microglial EGFP expression and astrocyte-specific expression of the genetically encoded Ca2+ sensor GCaMP3. CBD (10 mg/kg, intraperitoneally) prevented ischemia-induced neurological impairment, reducing the neurological deficit score from 2.0 ± 1.2 to 0.8 ± 0.8, and protected against neurodegeneration, as shown by the reduction (more than 70%) in Fluoro-Jade C staining (18.8 ± 7.5 to 5.3 ± 0.3). CBD reduced ischemia-induced microglial activation assessed by changes in soma area and total branch length, and exerted a balancing effect on astroglial Ca2+ signals. Our findings indicate that the neuroprotective effects of CBD may occur in the subacute phase of ischemia, and reinforce its strong anti-inflammatory property. Nevertheless, its mechanism of action on glial cells still requires further studies.

Cannabidiol Confers Neuroprotection in Rats in a Model of Transient Global Cerebral Ischemia: Impact of Hippocampal Synaptic Neuroplasticity.

Evidence for the clinical use of neuroprotective drugs for the treatment of cerebral ischemia (CI) is still greatly limited. Spatial/temporal disorientation and cognitive dysfunction are among the most prominent long-term sequelae of CI. Cannabidiol (CBD) is a non-psychotomimetic constituent of Cannabis sativa that exerts neuroprotective effects against experimental CI. The present study investigated possible neuroprotective mechanisms of action of CBD on spatial memory impairments that are caused by transient global cerebral ischemia (TGCI) in rats. Hippocampal synaptic plasticity is a fundamental mechanism of learning and memory. Thus, we also evaluated the impact of CBD on neuroplastic changes in the hippocampus after TGCI. Wistar rats were trained to learn an eight-arm aversive radial maze (AvRM) task and underwent either sham or TGCI surgery. The animals received vehicle or 10 mg/kg CBD (i.p.) 30 min before surgery, 3 h after surgery, and then once daily for 14 days. On days 7 and 14, we performed a retention memory test. Another group of rats that received the same pharmacological treatment was tested in the object location test (OLT). Brains were removed and processed to assess neuronal degeneration, synaptic protein levels, and dendritic remodeling in the hippocampus. Cannabidiol treatment attenuated ischemia-induced memory deficits. In rats that were subjected to TGCI, CBD attenuated hippocampal CA1 neurodegeneration and increased brain-derived neurotrophic factor levels. Additionally, CBD protected neurons against the deleterious effects of TGCI on dendritic spine number and the length of dendritic arborization. These results suggest that the neuroprotective effects of CBD against TGCI-induced memory impairments involve changes in synaptic plasticity in the hippocampus.

Involvement of dopamine D2 and glutamate NMDA receptors in the antidepressant-like effect of amantadine in mice.

The present study investigated the pharmacological mechanisms of the antidepressant-like effects of amantadine in mice and their influence on hippocampal neurogenesis. To improve the translational validity of preclinical results, reproducibility across laboratories and replication in other animal models and species are crucial. Single amantadine administration at doses of 50 and 75 mg/kg resulted in antidepressant-like effects in mice in the tail suspension test (TST), reflected by an increase in immobility time. The effects of amantadine were seen at doses that did not alter locomotor activity. The tyrosine hydroxylase inhibitor α-methyl-ρ-tyrosine did not influence the anti-immobility effect of amantadine in the TST. Pretreatment with the α1 adrenergic receptor antagonist prazosin, ß adrenergic receptor antagonist propranolol, α2 adrenergic receptor antagonist yohimbine, and α2 adrenergic receptor agonist clonidine did not alter the antidepressant-like effect of amantadine. However, amantadine's effect was blocked by the dopamine D2 receptor antagonist haloperidol and glutamate receptor agonist N-methyl-D-aspartate (NMDA). Repeated amantadine administration (50 mg/kg) also exerted an antidepressant-like effect, paralleled by an increase in hippocampal neurogenesis. The present results demonstrate that the antidepressant-like effects of amantadine may be mediated by its actions on D2 and NMDA receptors and likely involve hippocampal neurogenesis.

Neuroinflammation in Ischemic Stroke: Inhibition of cAMP-Specific Phosphodiesterases (PDEs) to the Rescue.

Ischemic stroke is caused by a thromboembolic occlusion of a major cerebral artery, with the impaired blood flow triggering neuroinflammation and subsequent neuronal damage. Both the innate immune system (e.g., neutrophils, monocytes/macrophages) in the acute ischemic stroke phase and the adaptive immune system (e.g., T cells, B cells) in the chronic phase contribute to this neuroinflammatory process. Considering that the available therapeutic strategies are insufficiently successful, there is an urgent need for novel treatment options. It has been shown that increasing cAMP levels lowers neuroinflammation. By inhibiting cAMP-specific phosphodiesterases (PDEs), i.e., PDE4, 7, and 8, neuroinflammation can be tempered through elevating cAMP levels and, thereby, this can induce an improved functional recovery. This review discusses recent preclinical findings, clinical implications, and future perspectives of cAMP-specific PDE inhibition as a novel research interest for the treatment of ischemic stroke. In particular, PDE4 inhibition has been extensively studied, and is promising for the treatment of acute neuroinflammation following a stroke, whereas PDE7 and 8 inhibition more target the T cell component. In addition, more targeted PDE4 gene inhibition, or combined PDE4 and PDE7 or 8 inhibition, requires more extensive research.

Persistence of the extinction of fear memory requires late-phase cAMP/PKA signaling in the infralimbic cortex.

Fear extinction is a form of new learning that inhibits expression of the original fear memory without erasing the conditioned stimulus-unconditioned stimulus association. Much is known about the mechanisms that underlie the acquisition of extinction, but the way in which fear extinction is maintained has been scarcely explored. Evidence suggests that protein kinase A (PKA) in the frontal cortex might be related to the persistence of extinction. Phosphodiesterase-4 (PDE4) specifically hydrolyzes cyclic adenosine monophosphate (cAMP). The present study evaluated the effect of the selective PDE4 inhibitor roflumilast (ROF; 0.01, 0.03, and 0.1 mg/kg given i.p.) on acquisition and consolidation of the extinction of fear memory in male Wistar rats in a contextual fear conditioning paradigm. When administered before acquisition, 0.1 mg/kg ROF disrupted short-term (1 day) extinction recall. In contrast, 0.03 mg/kg ROF administration in the late consolidation phase (3 h after extinction learning) but not in the early phase immediately after learning improved long-term extinction recall at 11 days, suggesting potentiation of the persistence of extinction. This effect of ROF requires the first (day 1) exposure to the context. A similar effect was observed when 9 ng ROF or 30 µM 8-bromoadenosine 3',5'-cAMP (PKA activator) was directly infused in the infralimbic cortex (IL), a brain region necessary for memory extinction. The PKA activity-dependent ROF-induced effect in the IL was correlated with an increase in its brain-derived neurotrophic factor (BDNF) protein expression, while blockade of PKA with 10 µM H89 in the IL abolished the ROF-induced increase in BDNF expression and prevented the effect of ROF on extinction recall. These effects were not associated with changes in anxiety-like behavior or general exploratory behavior. Altogether, these findings suggest that cAMP-PKA activity in the IL during the late consolidation phase after extinction learning underlies the persistence of extinction.

Postischemic fish oil treatment restores dendritic integrity and synaptic proteins levels after transient, global cerebral ischemia in rats.

We previously found that fish oil (FO) facilitated memory recovery in the absence of pyramidal neuron rescue after transient, global cerebral ischemia (TGCI). Fish oil preserved the expression of microtubule-associated protein 2 (MAP-2), suggesting a relationship between dendritic plasticity and memory recovery that is mediated by FO after TGCI. The present study examined whether postischemic treatment with FO prevents ischemia-induced loss of dendritic processes in remaining pyramidal neurons. The effects of FO on neuroplasticity-related proteins were also examined after TGCI. Rats were subjected to TGCI (15 min, four-vessel occlusion model) and then received vehicle or FO (300 mg/kg docosahexaenoic acid) once daily for 7 days. The first dose was administered 4 h postischemia. Golgi-Cox staining was used to evaluate dentrict morphology in the pyramidal neurons of hippocampus (CA1 and CA3 subfields) and prefrontal cortex (PFC). Neuronal nuclei protein (NeuN), brain-derived neurotrophic factor (BDNF), growth-associated protein 43 (GAP-43), synaptophysin (SYP), and postsynaptic density protein 95 (PSD-95) levels were measured by Western blot in both structures. Fifteen minutes of TGCI reduced consistently the length of dendrites, number of dendritic branches and dendritic spine density (average of 25%, 43%, 32%, respectively) 7, 14, and 21 days postischemia, indicating that they did not recover spontaneously. This outcome of TGCI was reversed by FO treatment, an effect that was sustained even after treatment cessation. The NeuN and BDNF protein levels were reduced in both the hippocampus and PFC, which were recovered by FO treatment. GAP-43 protein levels decreased after ischemia in the PFC only, and this effect was also mitigated by FO. Neither SYP nor PSD-95 levels were altered by ischemia, but PDS-95 levels almost doubled after FO treatment in the ischemic group. These data support our hypothesis that synaptic plasticity at the level of dendrites may at least partially underlie the memory-protective effect of FO after TGCI and strengthen the possibility that FO has therapeutic potential for treating the sequelae of brain ischemia/reperfusion injury.

Ethyl-acetate fraction of Trichilia catigua protects against oxidative stress and neuroinflammation after cerebral ischemia/reperfusion.

ETHNOPHARMACOLOGICAL RELEVANCE: Trichilia catigua A. Juss (Meliaceae) preparations have been used in folk medicine to alleviate fatigue, stress, and improve memory. Antinociceptive, antiinflammatory, and in vitro neuroprotective effects have been observed in animals. Cerebral ischemia/reperfusion (I/R) leads to severe neuropsychological deficits that are largely associated with oxidative stress, inflammation and neurodegeneration. We reported previously that an ethyl-acetate fraction (EAF) of T. catigua reduced brain ischemia-induced learning and memory impairments in the absence of histological protection. AIM OF THE STUDY: Continuing those studies, here we aimed to investigate the antioxidant and antiinflammatory properties of T. catigua in an in vivo model of I/R. MATERIAL AND METHODS: Rats were subjected to 15 min of brain ischemia (4-VO model) followed by up to 15 days of reperfusion. Vehicle was given by gavage 30 min before ischemia and at 1 h of reperfusion. In a first experiment, brain ischemia-induced changes in oxidative stress markers, i.e., reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and protein carbonyl groups (PCGs) were measured on days 1, 3, and 5 post-ischemia. Similar time course analysis was done for neuroinflammation markers, i.e., microglia (OX42 immunorreactivity) and astrocytes (GFAP immunorreactivity), in the hippocampus. In a second experiment, the time points at which these markers of oxidative stress and neuroinflammation peaked were used to test the effects of T. catigua (400 mg/kg, p.o.). RESULTS: Oxidative stress markers peaked on day 1 post-ischemia. GSH decreased (-23.2%) while GSSG increased (+ 71.1%), which yielded a significant reduction in the GSH/GSSG ratio (-39.1%). The activity of CAT was largely reduced by ischemia (-54.6% to -65.1%), while the concentration of PCG almost doubled in the brain of ischemic rats (+99.10%) in comparison to sham. Treatment with the EAF of T. catigua normalized these changes in oxidative markers to the control levels (GSH: +27.5%; GSSG: -23.8%; GSH/GSSG: +44.6%; PCG: -80.3%). In the hippocampus, neuroinflammation markers peaked on day 5 post-ischemia, with microglial and astrocytic responses increasing to 54.8% and 37.1%, respectively. The elevation in glial cells response was completely prevented by EAF. CONCLUSION: These results demonstrate that T. catigua has both antioxidant and antiinflammatory activities after transient global cerebral ischemia in rats, which may contribute to the previously reported memory protective effect of T. catigua.

Pioglitazone reduces mortality, prevents depressive-like behavior, and impacts hippocampal neurogenesis in the 6-OHDA model of Parkinson's disease in rats.

Deficiencies in adult hippocampal neurogenesis have been suggested to be a possible pathophysiological mechanism that underlies depressive symptoms that are often observed in patients with Parkinson's disease (PD). Pioglitazone, a selective peroxisome proliferator-activated receptor γ (PPAR-γ) agonist, has been shown to exert antiinflammatory and antidepressant effects and modulate neural plasticity in several neurodegenerative disorders. The present study investigated the effects of pioglitazone on depressive phenotypes and adult hippocampal neurogenesis in a rat model of PD that was induced by bilateral 6-hydroxydopamine (6-OHDA) infusions in the substantia nigra pars compact (SNpc). Rats with SNpc and ventral tegmental area (VTA) neurodegeneration exhibited despair-like behavior, concomitant with persistent microglial activation in the hippocampus. Pioglitazone reduced the rate of mortality and attenuated microglial activation in the early phase of 6-OHDA-induced nigral lesions. Pioglitazone exerted antidepressant-like effects and increased the survival of neurons in the hippocampus in rats with nigral lesions. These results indicate that pioglitazone exerts neuroprotective effects by facilitating hippocampal neurogenesis in 6-OHDA-lesioned rats, which might contribute to its antidepressant-like effect.

Ethyl-acetate fraction of Trichilia catigua restores long-term retrograde memory and reduces oxidative stress and inflammation after global cerebral ischemia in rats.

We originally reported that an ethyl-acetate fraction (EAF) of Trichilia catigua prevented the impairment of water maze learning and hippocampal neurodegeneration after transient global cerebral (TGCI) in mice. We extended that previous study by evaluating whether T. catigua (i) prevents the loss of long-term retrograde memory assessed in the aversive radial maze (AvRM), (ii) confers hippocampal and cortical neuroprotection, and (iii) mitigates oxidative stress and neuroinflammation in rats that are subjected to the four vessel occlusion (4-VO) model of TGCI. In the first experiment, naive rats were trained in the AvRM and then subjected to TGCI. The EAF was administered orally 30min before and 1h after TGCI, and administration continued once per day for 7days post-ischemia. In the second experiment, the EAF was administered 30min before and 1h after TGCI, and protein carbonylation and myeloperoxidase (MPO) activity were assayed 24h and 5days later, respectively. Retrograde memory performance was assessed 8, 15, and 21days post-ischemia. Ischemia caused persistent retrograde amnesia, and this effect was prevented by T. catigua. This memory protection (or preservation) persisted even after the treatment was discontinued, despite the absence of histological neuroprotection. Protein carbonyl group content and MPO activity increased around 43% and 100%, respectively, after TGCI, which were abolished by the EAF of T. catigua. The administration of EAF did not coincide with the days of memory testing. The data indicate that antioxidant and/or antiinflammatory actions in the early phase of ischemia/reperfusion contribute to the long-term antiamnesic effect of T. catigua.

Postischemic fish oil treatment confers task-dependent memory recovery.

A series of our previous studies demonstrated that fish oil (FO), equivalent to 300mg/kg docosahexahenoic acid (DHA), facilitates memory recovery after transient, global cerebral ischemia (TGCI) in the aversive radial maze (AvRM). The present study sought to address two main issues: (i) whether the memory-protective effect of FO that has been observed in the AvRM can be replicated in the passive avoidance test (PAT) and object location test (OLT) and (ii) whether FO at doses that are lower than those used previously can also prevent TGCI-induced memory loss. In Experiment 1, naive rats were trained in the PAT, subjected to TGCI (4-vessel occlusion model), and tested for retrograde memory performance 8 and 15days after ischemia. Fish oil (300mg/kg/day DHA) was given orally for 8days. The first dose was delivered 4h postischemia. In Experiment 2, the rats were subjected to TGCI, treated with the same FO regimen, and then trained and tested in the OLT. In Experiment 3, the rats were trained in the AvRM, subjected to TGCI, administered FO (100, 200, and 300mg/kg DHA), and tested for memory performance up to 3weeks after TGCI. At the end of the behavioral tests, the brains were examined for neurodegeneration and neuroblast proliferation. All of the behavioral tests (PAT, OLT, and AvRM) were sensitive to ischemia, but only the AvRM was able to detect the memory-protective effect of FO. Ischemia-induced neurodegeneration and neuroblast proliferation were unaffected by FO treatment. These results suggest that (i) the beneficial effect of FO on memory recovery after TGCI is task-dependent, (ii) doses of FO<300mg/kg DHA can protect memory function in the radial maze, and (iii) cognitive recovery occurs in the absence of neuronal rescue and/or hippocampal neurogenesis.

Myricitrin induces antidepressant-like effects and facilitates adult neurogenesis in mice.

Myricitrin (MYR) is a natural flavonoid that inhibits nitric oxide (NO) transmission and has an atypical antipsychotic-like profile in animal models. Considering that several NO inhibitors exert antidepressant-like effects, the present study evaluated the antidepressant-like effect of MYR (3-30mg/kg) in the tail suspension test (TST). Because of the putative relationship between adult neurogenesis and antidepressant activity, we also assessed cell proliferation, survival, and differentiation in adult neurogenic niches, including the subgranular zone (SGZ) and subventricular zone (SVZ). Similar to the positive control imipramine (IMI; 10mg/kg), repeated treatment with 10mg/kg MIR but not acute treatment reduced immobility time in the TST, indicating an antidepressant-like effect. No effect on general motor activity was observed. Myricitrin also facilitated cell proliferation in the SGZ of the hippocampal dentate gyrus and SVZ. In the SGZ, MYR increased the number of doublecortin- and 5-bromo-2'-deoxyuridine/neuronal nuclei-positive cells. Our results suggest that MYR facilitates hippocampal neurogenesis, which might contribute to its antidepressant-like effect and atypical antipsychotic-like profile.

Cannabidiol reduces neuroinflammation and promotes neuroplasticity and functional recovery after brain ischemia.

This study investigated the effects of cannabidiol (CBD), a non-psychotomimetic phytochemical present in Cannabis sativa, on the cognitive and emotional impairments induced by bilateral common carotid artery occlusion (BCCAO) in mice. Using a multi-tiered behavioral testing battery during 21days, we found that BCCAO mice exhibited long-lasting functional deficits reflected by increase in anxiety-like behavior (day 9), memory impairments (days 12-18) and despair-like behavior (day 21). Short-term CBD 10mg/kg treatment prevented the cognitive and emotional impairments, attenuated hippocampal neurodegeneration and white matter (WM) injury, and reduced glial response that were induced by BCCAO. In addition, ischemic mice treated with CBD exhibited an increase in the hippocampal brain derived neurotrophic factor (BDNF) protein levels. CBD also stimulated neurogenesis and promoted dendritic restructuring in the hippocampus of BCCAO animals. Collectively, the present results demonstrate that short-term CBD treatment results in global functional recovery in ischemic mice and impacts multiple and distinct targets involved in the pathophysiology of brain ischemic injury.

Postischemic fish oil treatment restores long-term retrograde memory and dendritic density: An analysis of the time window of efficacy.

We reported that fish oil (FO) prevented the loss of spatial memory caused by transient, global cerebral ischemia (TGCI), provided the treatment covered the first days prior to and after ischemia. Continuing these studies, trained rats were subjected to TGCI, and FO was administered for 10days, with a time window of efficacy (TWE) of 4, 8 or 12h post-ischemia. Retrograde memory was assessed up to 43days after TGCI. In another experiment, ischemic rats received FO with a 4- or 12-h TWE, and dendritic density was assessed in the hippocampus and cerebral cortex. The brain lipid profile was evaluated in sham-operated and ischemic rats that were treated with FO or vehicle with a 4-h TWE. Ischemia-induced retrograde amnesia was prevented by FO administration that was initiated with either a 4- or 8-h TWE. Fish oil was ineffective after a 12-h TWE. Independent of the TWE, FO did not prevent ischemic neuronal death. In the hippocampus, but not cerebral cortex, TGCI-induced dendritic loss was prevented by FO with a 4-h TWE but not 12-h TWE. The level of docosahexaenoic acid almost doubled in the hippocampus in ischemic, FO-treated rats (4-h TWE). The data indicate that (i) the anti-amnesic effect of FO can be observed with a TWE of up to 8h, (ii) the stimulation of dendritic neuroplasticity may have contributed to this effect, and (iii) DHA in FO may be the main active constituent in FO that mediates the cognitive and neuroplasticity effects on TGCI.

Robust and enduring atorvastatin-mediated memory recovery following the 4-vessel occlusion/internal carotid artery model of chronic cerebral hypoperfusion in middle-aged rats.

Chronic cerebral hypoperfusion (CCH) is a common condition associated with the development and/or worsening of age-related dementia.We previously reported persistent memory loss and neurodegeneration after CCH in middle-aged rats. Statin-mediated neuroprotection has been reported after acute cerebral ischemia. Unknown, however, is whether statins can alleviate the outcome of CCH. The present study investigated whether atorvastatin attenuates the cognitive and neurohistological outcome of CCH. Rats (12­15 months old) were trained in a non-food-rewarded radial maze, and then subjected to CCH. Atorvastatin (10 mg/kg, p.o.) was administered for 42 days or 15 days, beginning 5 h after the first occlusion stage. Retrograde memory performance was assessed at 7, 14, 21, 28, and 35 days of CCH, and expressed by "latency," "number of reference memory errors" and "number of working memory errors." Neurodegeneration was then examined at the hippocampus and cerebral cortex. Compared to sham, CCH caused profound and persistent memory loss in the vehicle-treated groups, as indicated by increased latency (91.2% to 107.3%) and number of errors (123.5% to 2508.2%), effects from which the animals did not spontaneously recover across time. This CCH-induced retrograde amnesia was completely prevented by atorvastatin (latency: −4.3% to 3.3%; reference/working errors: −2.5% to 45.7%), regardless of the treatment duration. This effect was sustained during the entire behavioral testing period (5 weeks), even after discontinuing treatment. This robust and sustained memory-protective effect of atorvastatin occurred in the absence of neuronal rescue (39.58% to 56.45% cell loss). We suggest that atorvastatin may be promising for the treatment of cognitive sequelae associated with CCH.