Search

Background Cannabinoid-based therapy has been shown to be promising and is emerging as crucial for the treatment of cognitive deficits, mental illnesses, and many diseases considered incurable. There is a need to find an appropriate therapy for Alzheimer’s disease, and cannabinoid-based therapy appears to be a feasible possibility. Case presentation This report addresses the beneficial effect of cannabinoids in microdoses on improving memory and brain functions of a patient with mild-stage Alzheimer’s disease. The patient is a 75-year-old white man presenting with main symptoms of memory deficit, spatial and temporal disorientation, and limited daily activity. The experimental therapeutic intervention was carried out for 22 months with microdoses of a cannabis extract containing cannabinoids. Clinical evaluations using Mini-Mental State Examination and Alzheimer’s Disease Assessment Scale-Cognitive Subscale were performed. Conclusions Here we provide original evidence that cannabinoid microdosing could be effective as an Alzheimer’s disease treatment while preventing major side effects. This is an important step toward dissociating cannabinoids’ health-improving effects from potential narcotic-related limitations.

N-methyl D-aspartate (NMDA) administered at subtoxic dose plays a protective role against neuronal excitotoxicity, a mechanism described as preconditioning. Since the activation of adenosinergic receptors influences the achievement of NMDA preconditioning in the hippocampus, we evaluated the potential functional interplay between adenosine A

Previous studies have demonstrated that targeting bradykinin receptors is a promising strategy to counteract the cognitive impairment related with aging and Alzheimer's disease (AD). The hippocampus is critical for cognition, and abnormalities in this brain region are linked to the decline in mental ability. Nevertheless, the impact of bradykinin signaling on hippocampal function is unknown. Therefore, we sought to determine the role of hippocampal bradykinin receptors B1R and B2R on the cognitive decline of middle-aged rats. Twelve-month-old rats exhibited impaired ability to acquire and retrieve spatial information in the Morris water maze task. A single intra-hippocampal injection of the selective B1R antagonist des-Arg9-[Leu8]-bradykinin (DALBK, 3 nmol), but not the selective B2R antagonist D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-BK (Hoe 140, 3 nmol), reversed the spatial learning and memory deficits on these animals. However, both drugs did not affect the cognitive function in 3-month-old rats, suggesting absence of nootropic properties. Molecular biology analysis revealed an up-regulation of B1R expression in the hippocampal CA1 sub-region and in the pre-frontal cortex of 12-month-old rats, whereas no changes in the B2R expression were observed in middle-aged rats. These findings provide new evidence that inappropriate hippocampal B1R expression and activation exert a critical role on the spatial learning and memory deficits in middle-aged rats. Therefore, selective B1R antagonists, especially orally active non-peptide antagonists, may represent drugs of potential interest to counteract the age-related cognitive decline.

N-methyl D-aspartate (NMDA) administered at subtoxic dose plays a protective role against neuronal excitotoxicity, a mechanism described as preconditioning. Since the activation of adenosinergic receptors influences the achievement of NMDA preconditioning in the hippocampus, we evaluated the potential functional interplay between adenosine A1 and A2A receptors (A1R and A2AR) activities and NMDA preconditioning. Adult male Swiss mice received saline (NaCl 0.9 g%, i.p.) or a nonconvulsant dose of NMDA (75 mg/kg, i.p.) and 24 h later they were treated with the one of the ligands: A1R agonist (CCPA, 0.2 mg/kg, i.p.) or antagonist (DPCPX, 3 mg/kg, i.p.), A2AR agonist (CGS21680, 0.05 mg/kg, i.p.) or antagonist (ZM241385, 0.1 mg/kg, i.p.) and subjected to contextual fear conditioning task. Binding properties and content of A2AR and glutamate uptake were assessed in the hippocampus of mice subjected to NMDA preconditioning. Treatment with CGS21680 increased the time of freezing during the exposure of animals to the new environment. NMDA preconditioning did not affect the freezing time of mice per se, but it prevented the response observed after the activation of A2AR. Furthermore, the activation of A2AR by CGS21680 after the preconditioning blocked the increase of glutamate uptake induced by NMDA preconditioning. The immunodetection of A2AR in total hippocampal homogenates showed no significant differences evoked by NMDA preconditioning and did not alter A2AR maximum binding for the selective ligand [3H]CGS21680. These results demonstrate changes in A2AR functionality in mice following NMDA preconditioning.

This meta-analysis paper describes the analysis of observational clinical studies on the treatment of refractory epilepsy with cannabidiol (CBD)-based products. Beyond attempting to establish the safety and efficacy of such products, we also investigated if there is enough evidence to assume any difference in efficacy between CBD-rich extracts compared to purified CBD products. The systematic search took place in February/2017 and updated in December/2017 using the keywords “epilepsy” or “Dravet” or “Lennox-Gastaut” or “CDKL5” combined with “Cannabis,” “cannabinoid,” “cannabidiol,” or “CBD” resulting in 199 papers. The qualitative assessment resulted in 11 valid references, with an average impact factor of 8.1 (ranging from 1.4 to 47.8). The categorical data of a total of 670 patients were analyzed by Fischer test. The average daily dose ranged between 1 and 50 mg/kg, with treatment length from 3 to 12 months (mean 6.2 months). Two thirds of patients reported improvement in the frequency of seizures (399/622, 64%). There were more reports of improvement from patients treated with CBD-rich extracts (318/447, 71%) than patients treated with purified CBD (81/175, 46%), with statistical significance (p < 0.0001). Nevertheless, when the standard clinical threshold of a “50% reduction or more in the frequency of seizures” was applied, only 39% of the individuals were considered “responders,” and there was no difference (p = 0.52) between treatments with CBD-rich extracts (122/330, 37%) and purified CBD (94/223, 42%). Patients treated with CBD-rich extracts reported lower average dose (6.0 mg/kg/day) than those using purified CBD (25.3 mg/kg/day). The reports of mild (158/216, 76% vs. 148/447, 33%, p < 0.001) and severe (41/155, 26% vs. 23/328, 7%, p < 0.0001) adverse effects were more frequent in products containing purified CBD than in CBD-rich extracts. CBD-rich extracts seem to present a better therapeutic profile than purified CBD, at least in this population of patients with refractory epilepsy. The roots of this difference is likely due to synergistic effects of CBD with other phytocompounds (aka Entourage effect), but this remains to be confirmed in controlled clinical studies.

Potential clinical benefits of CBD-rich Cannabis extracts over purified CBD in treatment-resistant epilepsy: observational data meta-analysisDifferent therapies involving cannabinoid compounds have become popular on the past few years, particularly the use of canabidiol (CBD) based products for the treatment of child refractory epilepsy. In this segment we highlight genetic disorders such as the Dravet Syndrome, which has received a lot of attention in Brazil. Our country has been giving visibility for this issue after the public discussion regarding the patient Anne Fischer, who benefited from a treatment with hemp based products, imported from the United States of America as a nutritional supplement, and still unregistered in Brazil. To this moment there is no cannabinoid based product registered for clinical indication for epilepsy, so patients have at their disposal products considered nutritional supplements, in general produced from a type of Cannabis known as “hemp”, which are commercialized in Brazil through medical prescription. Despite several anecdotal evidences from patients and family members, until now there is no consensus on medical literature over the efficacy and safety of these products. Some observational studies are available on scientific literature, but there is still a scarcity of clinical studies conducted under the logic, rigor and organization necessary for clinical trial dedicated to the register of a pharmaceutical product. The objective of this paper is to describe the analysis of several observational clinical studies available on the literature regarding the treatment of child refractory epilepsy with cannabinoid based products. Beyond attempting to establish the safety and efficacy of such products, when possible, the present analysis also intended to investigate if there is enough evidence between the different aspects of safety and efficacy between CBD enriched extracts compared to purified CBD products. Results: a systematic search for papers in the “PubMed” search system with the words “Dravet”, "Lennox-Gastaut" and "epilepsy" combined with the terms "Cannabis", "cannabinoid" and "child" yielded 30 papers. From those, 24 were not considered for the systematic review, for not having valid content (13), for being opinion only papers (6), showed not clinical data (4) and reported different subjects (1), resulting in 6 valid papers published between 2013 and 2016. One additional study was in press at the moment of the search was added manually (1) resulting in 7 valid references for analysis, with an average impact factor of 5,9 (2,3 to 21,8). Public data from partial reports of controlled randomized studies conducted in order to register a medication (2) were also considered, when appropriated and were mentioned in the text. The categorical data were analyzed by the Fischer test. Overall, the papers analyzed report observational clinical data of 442 patients, treated with CBD rich extracts or purified CBD, with he average daily dose between 1 and 50 mg/kg, with treatment length from 3 to 12 months (average of 6,2 months). A considerable amount of 66% (292/442) of the patients reported improvement in the frequency of convulsive crisis. There were more reports of improvement from patients treated with purified CBD (242/285) than patients treated with purified CBD (68/157), with statistical significance (p*Presented as an abstract and lecture to the 2017 CannMed event, at the Harvard Medical School, Boston, USA, in may 2017.

Inosine is an endogenous nucleoside that has anti-inflammatory and antinociceptive properties. Inosine is a metabolite of adenosine, and some of its actions suggest the involvement of adenosine A1 receptors (A1Rs). The purpose of this study was to better understand mechanisms of inosine-induced antinociception by investigating the role of A1Rs and purine metabolism inhibitors. Inosine antinociception was evaluated using the formalin test in mice. An A1R-selective antagonist (DPCPX), A1R knockout mice (gene deletion) and mice with A1R reduced expression (antisense oligonucleotides) were used to assess the role of A1Rs in the antinociceptive action of inosine. Binding assays were performed to compare the affinity of inosine and adenosine for A1Rs. Finally, the role of adenosine and inosine breakdown was assessed using deoxycoformycin (DCF) and forodesine (FDS) as enzymatic inhibitors of adenosine deaminase and purine nucleoside phosphorylase, respectively. Inosine induced antinociception in the formalin test when given by systemic, spinal and peripheral routes. Systemically, inosine exhibited a potency similar to adenosine, and its effects were inhibited by DPCPX. Inosine did not induce antinociception in A1R knockout mice or in mice with reduced A1R expression. In binding studies, inosine bound to A1Rs with an affinity similar to adenosine. DCF had no effect on inosine actions. FDS augmented the antinociceptive effect of a low systemic dose of inosine and, at a higher dose, induced antinociception by itself. Collectively, these data indicate that inosine is an agonist for A1Rs with antinociceptive properties and a potency similar to adenosine and can be considered another endogenous ligand for this receptor.

The endocannabinoid (eCB) and glucocorticoid systems contribute to the modulation of emotional states. Noteworthy, glucocorticoid hormones are released by adrenal glands during stressful events and endocannabinoids are released in the brain during fear-conditioned responses. Since it was already suggested that glucocorticoids may trigger the release of endocannabinoids in the brain, our objective was to investigate whether the interaction between these neuromodulatory systems contributes to the decrease of conditioned freezing behavior over successive 9-min exposures to the conditioning context. Present results suggest a bidirectional interdependence between glucocorticoid and endocannabinoid systems. CB1 receptors blockade prevents glucocorticoid-induced facilitation of conditioned freezing decrease and inhibition of glucocorticoid synthesis renders boosting of endocannabinoid signaling innocuous, while preserving the efficacy of direct CB1 receptors activation by an exogenous cannabinoid agonist. This suggests that CB1 receptors are somehow "downstream" to glucocorticoid release, which in its turn, is reduced by CB1 activation, contributing to the persistent reduction of conditioned freezing responses.

Neuromarketing applies neuroscientific methods to marketing-relevant questions. Although it is currently fashionable, using neuroscience tools to inform about real life scenarios it's not a trivial quest.Assessment of marketing preferences by structured interviews allows only a limited perspective, with low external validity. Neuroscience might provide methods that overcome the need for verbalisations through measurementof brain activations. Here we discuss the potential of this emerging field and the issues that limit our enthusiasm at the current stage. Many questions are still open and claiming for creative approaches that improve scientific knowledge, while creating actual value to customers.

Cellular prion protein (PrP(C) ) is widely expressed in the brain. Although the precise role of PrP(C) remains uncertain, it has been proposed to be a pivotal modulator of neuroplasticity events by regulating the glutamatergic and serotonergic systems. Here we report the existence of neurochemical and functional interactions between PrP(C) and the dopaminergic system. PrP(C) was found to co-localize with dopaminergic neurons and in dopaminergic synapses in the striatum. Furthermore, the genetic deletion of PrP(C) down-regulated dopamine D1 receptors and DARPP-32 density in the striatum and decreased dopamine levels in the prefrontal cortex of mice. This indicates that PrP(C) affects the homeostasis of the dopaminergic system by interfering differently in different brain areas with dopamine synthesis, content, receptor density and signaling pathways. This interaction between PrP(C) and the dopaminergic system prompts the hypotheses that the dopaminergic system may be implicated in some pathological features of prion-related diseases and, conversely, that PrP(C) may play a role in dopamine-associated brain disorders.

Emotional learning is extremely important for the survival of an individual. However, once acquired, emotional associations are not always expressed. The regulation of emotional responses under different environmental conditions is essential for mental health. Indeed, pathologic feelings of fear and anxiety are defining features of many serious psychiatric illness, including post-traumatic stress disorder (PTSD) and specific phobias. The simplest form of regulation of emotional responses is extinction, in which the conditioned response to a stimulus decreases when reinforcement (stimulus) is omitted. In addition to modulating basal anxiety states, recent studies suggest an important role for the endocannabinoid (eCB) and glucocorticoid systems in the modulation of emotional states and extinction of aversive memories in animals. The purpose of this review is to briefly outline the animal models of fear extinction and to describe how these have been used to examine the potential of extinction enhancing agents which specifically alter the eCB and glucocorticoid systems. Pharmacological manipulations of these systems by agents such as cannabinoid or glucocorticoid agonists can enhance the extinction process and avoid the retention of memories which have the potential to trigger trauma. A better understanding of these findings through animal models highlights the possibilities of using combined extinction enhancing agents in exposure-based psychotherapies for anxiety disorders related to inappropriate retention of aversive memories. This article is part of a special issue entitled 'Cognitive Enhancers'.

The development of exaggerated avoidance behavior is largely responsible for the decreased quality of life in patients suffering from anxiety disorders. Studies using animal models have contributed to the understanding of the neural mechanisms underlying the acquisition of avoidance responses. However, much less is known about its extinction. Here we provide evidence in mice that learning about the safety of an environment (i.e., safety learning) rather than repeated execution of the avoided response in absence of negative consequences (i.e., response extinction) allowed the animals to overcome their avoidance behavior in a step-down avoidance task. This process was context-dependent and could be blocked by pharmacological (3 mg/kg, s.c.; SR141716) or genetic (lack of cannabinoid CB1 receptors in neurons expressing dopamine D1 receptors) inactivation of CB1 receptors. In turn, the endocannabinoid reuptake inhibitor AM404 (3 mg/kg, i.p.) facilitated safety learning in a CB1-dependent manner and attenuated the relapse of avoidance behavior 28 days after conditioning. Safety learning crucially depended on endocannabinoid signaling at level of the hippocampus, since intrahippocampal SR141716 treatment impaired, whereas AM404 facilitated safety learning. Other than AM404, treatment with diazepam (1 mg/kg, i.p.) impaired safety learning. Drug effects on behavior were directly mirrored by drug effects on evoked activity propagation through the hippocampal trisynaptic circuit in brain slices: As revealed by voltage-sensitive dye imaging, diazepam impaired whereas AM404 facilitated activity propagation to CA1 in a CB1-dependent manner. In line with this, systemic AM404 enhanced safety learning-induced expression of Egr1 at level of CA1. Together, our data render it likely that AM404 promotes safety learning by enhancing information flow through the trisynaptic circuit to CA1.

There is increasing evidence that hypercholesterolemia during midlife may represent a predictor of subsequent mild cognitive impairments and dementia decades later. However, the exact mechanism underlying this phenomenon remains unknown since plasmatic cholesterol is not able to cross the blood-brain barrier. In the present study, we evaluated the hypothesis that cognitive impairments triggered by hypercholesterolemia during aging may be related to brain oxidative stress and altered brain acetylcholinesterase (AChE) activity. We also performed a neuropathological investigation in order to analyze whether the cognitive impairments may be associated with stroke-related features. To address these questions we used three- and fourteen-month-old low-density lipoprotein receptor-deficient mice (LDLr-/-). The current findings provide new evidence that aged LDLr-/- mice, exposed to over three-fold cholesterol levels from early life, show working, spatial reference, and procedural memory impairments, without alterations in motor function. Antioxidant imbalance and oxidative damage were evidenced by a marked increase in lipid peroxidation (thiobarbituric acid reactive substances levels) and glutathione metabolism (increase in glutathione levels, glutathione reductase, and glutathione peroxidase activities) together with a significant increase in the AChE activity in the prefrontal cortex of aged hypercholesterolemic LDLr-/- mice. Notably, hypercholesterolemia was not related to brain infarcts and neurodegeneration in mice, independent of their age. These observations provide new evidence that hypercholesterolemia during aging triggers cognitive impairments on different types of learning and memory, accompanied by antioxidant imbalance, oxidative damage, and alterations of cholinergic signaling in brain areas associated with learning and memory processes, particularly in the prefrontal cortex.

Background. Stroke occurs due to an interruption in cerebral blood supply affecting neuronal function. Body temperature on hospital admission is an important predictor of clinical outcome. Therapeutic hypothermia is promising in clinical settings for stroke neuroprotection. Methods. MEDLINE/PubMed, CENTRAL, Stroke Center, and ClinicalTrials.gov were systematically searched for hypothermia intervention induced by external or endovascular cooling for acute stroke. NIH Stroke Scale (NIHSS) and modified Rankin Scale (mRS) were the main stroke scales used, and mortality was also reported. A meta-analysis was carried out on stroke severity and mortality. Results. Seven parallel-controlled clinical trials were included in the meta-analysis. Sample sizes ranged from 18 to 62 patients, yielding a total of 288. Target temperature (~33°C) was reached within 3-4 hours. Stroke severity (Cohen's 𝑑 = − 0 . 1 7 , 95% CI: −0.42 to 0.08, 𝑃 = 0 . 3 2 ; I2 = 73%; Chi2 = 21.89, 𝑃 = 0 . 0 0 0 1 ) and mortality ( R R = 1 . 6 0 , 95% CI: 0.93 to 2.78, 𝑃 = 0 . 1 1 ; I 2 = 0%; Chi2 = 2.88, 𝑃 = 0 . 7 2 ) were not significantly affected by hypothermia. Discussion. Hypothermia does not significantly improve stroke severity; however, this finding should be taken with caution due to the high heterogeneity and limited number of included studies. No impact on mortality was observed.

The study of endocannabinoid pharmacology has proceeded from the discovery of Δ9-tetrahydrocannabinol, the main psychoactive compound in Cannabis sativa, to the identification of an endogenous endocannabinoid system that is essential for physiological modulation of neuronal functions. We have not yet achieved a complete understanding of the various roles of the endocannabinoids, but this is one of the fastest-growing fields in psychopharmacology. This review starts with a brief historical description of the discovery of the endocannabinoids and then focuses on recent pharmacological advances and recently discovered endocannabinoid mechanisms of action (e.g. functional selectivity, allosterism, and receptor trafficking). Finally, we will discuss the contention that the existence of evidence-based therapeutic applications for cannabinoids and the wide range of physiological functions affected by endocannabinoids suggests that the careful study of the endocannabinoid system may lead to the development of novel therapeutic drugs with higher societal acceptability and lower side effects profiles.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the decline in cognitive functions, but it is also related to emotional disturbances. Since pain experience results from a complex integration of sensory, cognitive and affective processes, it is not surprising that AD patients display a distinct pattern of pain responsivity. We evaluated whether mice treated with amyloid beta (Abeta) peptide-thought to be critical in the pathogenesis of AD-exhibit altered pain responses and its relation to altered emotionality. Mice received a single i.c.v. injection of vehicle (PBS) or Abeta fragment (1-40) (400pmol/mice) and after 30 days, they were evaluated in tests of pain (hotplate, footshock-sensitivity), learning/memory (water-maze), emotionality (elevated plus-maze, forced swim) and locomotion (open-field). Abeta(1-40)-treated mice presented similar latencies to the control group in the hotplate test and similar nociceptive flinch threshold in the footshock-sensitivity test. However, they presented an increased jump threshold in footshock-sensitivity, suggesting increased pain tolerance. Altered emotionality was observed in the elevated plus-maze (EPM) and forced-swim tests (FST), suggesting anxiogenic-like and depressive-like states, respectively. A multifactorial principal component analysis (PCA) revealed that jump threshold of the footshock-sensitivity test falls within 'Emotionality' and 'Pain', showing moderate correlation with each one of the components of behavior. Acute treatment with the antidepressant desipramine (10mg/kg, i.p.) reduced the jump threshold (i.e. pain tolerance) and time of immobility in FST (i.e. depressive-like state). Flinch threshold (i.e. pain sensitivity), locomotion and anxiety were not altered with desipramine treatment. These results suggest that Abeta(1-40) peptide increases pain tolerance, but not pain sensitivity in mice, which seems to be linked to alterations in cognitive/emotional components of pain processing.

The strain of spontaneously hypertensive rats (SHR) is considered a genetic model for the study of attention-deficit hyperactivity disorder (ADHD), as it displays hyperactivity, impulsivity and poorly sustained attention. Recently, we have shown the involvement of adenosinergic neuromodulation in the SHR's short-term and long-term memory impairments. In this study, we investigated the performance of male and female SHR in a modified version of the object-recognition task (using objects with different structural complexity) and compared them with Wistar rats, a widely used outbred rat strain for the investigation of learning processes. The suitability of the SHR strain to represent an animal model of ADHD, as far as mnemonic deficits are concerned, was pharmacologically validated by the administration of methylphenidate, the first-choice drug for the treatment of ADHD patients. The role of adenosine A1 and A2A receptors in object discrimination was investigated by the administration of caffeine (nonselective antagonist) or selective adenosine receptor antagonists. Wistar rats discriminated all the objects used (cube vs. pyramid; cube vs. T-shaped object), whereas SHR only discriminated the most structurally distinct pairs of objects (cube vs. pyramid). Pretraining administration of methylphenidate [2 mg/kg, intraperitoneal (i.p.)], caffeine (1-10 mg/kg, i.p.), the selective adenosine receptor antagonists DPCPX (8-cyclopenthyl-1,3-dipropylxanthine; A1 antagonist, 5 mg/kg, i.p.) and ZM241385 (A2A antagonist, 1.0 mg/kg, i.p.), or the association of ineffective doses of DPCPX (3 mg/kg) and ZM241385 (0.5 mg/kg), improved the performance of SHR in the object-recognition task. These findings show that the discriminative learning impairments of SHR can be attenuated by the blockade of either A1 or A2A adenosine receptors, suggesting that adenosinergic antagonists might represent potentially interesting drugs for the treatment of ADHD.

Rationale Previous studies demonstrated that pharmacological blockade of CB1 cannabinoid receptors decreases the extinction of conditioned fear and spatial memory in rodents. However, the effects of CB1 cannabinoid receptor activation in this response remain unclear. Objectives To evaluate the effects of the cannabinoid agonist WIN 55,212-2 (WIN) and the cannabinoid antagonist SR 147778 (SR) on the extinction of contextual fear memory in rats 24 h or 30 days after fear conditioning. Methods For fear conditioning, rats were placed in the conditioning chamber for 3 min and received a 1-s electric foot shock (1.5 mA). Retrieval testing consisted of a 3-min exposure to the conditioning chamber and extinction training consisted of successive 9-min exposures at 24-h intervals. Rats were also evaluated in the open field and water maze reversal task. Results The administration of SR (1.0 mg/kg, i.p.) and WIN (0.25 mg/kg, i.p.) before extinction training disrupted and facilitated, respectively, the extinction of 24 h contextual fear memory. These effects were not related to any disturbance in memory retrieval, unconditioned freezing expression, or locomotor activity. WIN (0.25 mg/kg, i.p.) also facilitated the extinction of 30-day-old contextual fear memory, while the prior administration of SR (0.2 mg/kg, i.p.) antagonized this response. The facilitative effect of WIN on memory extinction does not seem to be specific for contextual fear memory because it was also observed in the water maze reversal task. Conclusions These results suggest cannabinoid receptor agonists as potential drugs to treat anxiety disorders related to the retrieval of aversive memories.

Δ9-THC and synthetic cannabinoids produce memory impairment in humans as well as in laboratory animals. The high concentration of cannabinoid CB1 receptors and the presence of endocannabinoids in the hippocampus suggest that a cannabinoid neurochemical system may play a role in learning and memory processes. Thus, the objective of the present work was to study the effect of the cannabinoid antagonist SR141716A (SR) on memory acquisition, consolidation and retrieval in a recently developed elevated T-maze (ETM) model of anxiety and memory. In addition, we investigated whether pre-training SR administration was capable of reversing scopolamine-induced memory impairment. Adult male mice were exposed to the closed arm as many times as necessary for the animals to reach the avoidance criterion of remaining in the closed arm for 300 s; they were then tested (exposed to the closed arm) 24 h and 7 days after the training. SR (0.5, 1.0 or 2.0 mg/kg) was administered i.p. 20 min before the training, immediately after training or 20 min before the test in the mice. The elevated plus-maze (EPM) was used to investigate a possible influence of SR on locomotion and on the anxiety-related behavior. SR provoked memory improvement, which was observed when the drug was administered before (effect on memory acquisition/consolidation) or immediately after the training (effect on memory consolidation), but not when the drug was administered before the test (effect on memory retrieval). Also, SR administration reversed scopolamine-induced amnesia. These effects were observed in the absence of changes in locomotion or anxiety levels. Our results demonstrate that the blockade of cannabinoid receptors may improve memory acquisition and consolidation in the ETM model.

N-methyl-d-aspartate (NMDA) preconditioning is induced by subtoxic doses of NMDA and it promotes a transient state of resistance against subsequent lethal insults. Interestingly, this mechanism of neuroprotection depends on adenosine A1 receptors (A1R), since blockade of A1R precludes this phenomenon. In this study we evaluated the consequences of NMDA preconditioning on the hippocampal A1R biology (i.e. expression, binding properties and functionality). Accordingly, we measured A1R expression in NMDA preconditioned mice (75mg/kg, i.p.; 24h) and showed that neither the total amount of receptor, nor the A1R levels in the synaptic fraction was altered. In addition, the A1R binding affinity to the antagonist [(3)H] DPCPX was slightly increased in total membrane extracts of hippocampus from preconditioned mice. Next, we evaluated the impact of NMDA preconditioning on A1R functioning by measuring the A1R-mediated regulation of glutamate uptake into hippocampal slices and on behavioral responses in the open field and hot plate tests. NMDA preconditioning increased glutamate uptake into hippocampal slices without altering the expression of glutamate transporter GLT-1. Interestingly, NMDA preconditioning also induced antinociception in the hot plate test and both effects were reversed by post-activation of A1R with the agonist CCPA (0.2mg/kg, i.p.). NMDA preconditioning or A1R modulation did not alter locomotor activity in the open field. Overall, the results described herein provide new evidence that post-activation of A1R modulates NMDA preconditioning-mediated responses, pointing to the importance of the cross-talk between glutamatergic and adenosinergic systems to neuroprotection.

When 5-lipoxygenase (5-LO) is inhibited, roughly half of the CNS effect of the prototypic endocannabinoid anandamide (AEA) is lost. Therefore, we decided to investigate whether inhibiting this enzyme would influence physiological functions classically described as being under control of the endocannabinoid system. Although 5-LO inhibition by MK-886 reduced lipoxin A4 levels in the brain, no effect was found in the elevated plus maze (EPM), even at the highest possible doses, via i.p. (10 mg/kg,) or i.c.v. (500 pmol/2 µl) routes. Accordingly, no alterations in anxiety-like behavior in the EPM test were observed in 5-LO KO mice. Interestingly, aged mice, which show reduced circulating lipoxin A4 levels, were sensitive to MK-886, displaying an anxiogenic-like state in response to treatment. Moreover, exogenous lipoxin A4 induced an anxiolytic-like profile in the EPM test. Our findings are in line with other reports showing no difference between FLAP KO or 5-LO KO and their control strains in adult mice, but increased anxiety-like behavior in aged mice. We also show for the first time that lipoxin A4 affects mouse behavior. In conclusion, we propose an age-dependent relevancy of endogenous 5-LO derivatives in the modulation of anxiety-like behavior, in addition to a potential for exogenous lipoxin A4 in producing an anxiolytic-like state.

Posttraumatic stress disorder (PTSD) is characterized by the presence of three major symptom clusters: persistent fear memories, hyperarousal, and avoidance. With a passage of time after the trauma, PTSD patients show an increase in unspecific fear and avoidance, a phenomenon termed "fear generalization". It is not clear whether fear generalization arises from the time-dependent growth of hyperarousal or changes in associative fear. The present study investigated behavioral and neuroanatomical correlates of non-associative and associative fear memory one week vs. one month after a trauma in a mouse model of PTSD with immediate vs. delayed foot shock application. The immediate shock procedure led to a lower contextual fear, but did not influence the hyperarousal (i.e. increased acoustic startle responses) assessed within the first week after the trauma. Only delayed shocked mice demonstrated generalization of contextual fear and an increase in generalized avoidance behavior, with no changes in hyperarousal one month after trauma. We observed the same increase in c-Fos expression following delayed and immediate shock presentation within the lateral, basolateral, central amygdala and CA1, CA3 and dentate gyrus of hippocampus, suggesting that all of these structures contribute to the development of hyperarousal. Only basolateral amygdala and dentate gyrus appeared to be additionally involved in encoding of contextual information. In summary, our results demonstrate the independence of associative and non-associative trauma-related fear. They support the hypothesis that generalized fear emerges in consequence of forgetting specific stimulus attributes associated with the shock context.

Glucose-dependent insulinotropic polypeptide (GIP) is a 42-amino acid hormone, secreted from the enteroendocrine K cells, which has insulin-releasing and extra-pancreatic actions. GIP and its receptor present a widespread distribution in the mammalian brain where they have been implicated with synaptic plasticity, neurogenesis, neuroprotection and behavioral alterations. This review attempts to provide a comprehensive picture of the role of GIP in the central nervous system and to highlight recent findings from our group showing its potential involvement in neurological illnesses including epilepsies, Parkinson's disease and Alzheimer's disease.

The spontaneously hypertensive rat (SHR) is frequently used as an experimental model for the study of attention deficit hyperactivity disorder (ADHD) since it displays behavioural and neurochemical features of ADHD. Increasing evidence suggests that caffeine might represent an important therapeutic tool for the treatment of ADHD and we recently demonstrated that the acute administration of caffeine improves several learning and memory impairments in adult SHR rats. Here we further evaluated the potential of caffeine in ADHD therapy. Female Wistar (WIS) and SHR rats were treated with caffeine (3 mg/kg, i.p.) or methylphenidate (MPD, 2 mg/kg, i.p.) for 14 consecutive days during the prepubertal period (post-natal days 25–38) and they were tested later in adulthood in the object-recognition task. WIS rats discriminated all the objects used, whereas SHR were not able to discriminate pairs of objects with subtle structural differences. Chronic treatment with caffeine or MPD improved the object-recognition deficits in SHR rats. Surprisingly, these treatments impaired the short-term object-recognition ability in adult WIS rats. The present drug effects are independent of changes in locomotor activity, arterial blood pressure and body weight in both rat strains. These findings suggest that chronic caffeine treatment during prepubertal period confers long-term cognitive benefits in discriminative learning impairments of SHR, suggesting caffeine as an alternative therapeutic strategy for the early management of ADHD symptoms. Nevertheless, our results also emphasize the importance of a correct diagnosis and the caution in the use of stimulant drugs such as caffeine and MPD during neurodevelopment since they can disrupt discriminative learning in non-ADHD phenotypes.

Long-lasting presence of avoidance and emotional numbing are reliable behavioral markers for PTSD, but little is known about its psychological and biological underpinnings. We employed our recently established mouse model of PTSD (i) to study the emergence of avoidance behavior in the aftermath of a trauma, (ii) to disentangle the impact of context generalization vs. lack of motivation vs. novelty fear and (iii) to assess the therapeutic value of benzodiazepines and selective serotonin reuptake inhibitors (SSRIs). Specific conditioned avoidance to shock-paired odor turned into generalized avoidance after 28 days of fear incubation. Combination of habituation to the novel environment and extinction of contextual fear abolished both generalized and specific avoidance behavior. Chronic fluoxetine treatment partially reversed the phenotype, whereas acute treatment with diazepam did not. Our animal model may help understanding the mechanisms underlying psychological and biological mechanisms of PTSD for the benefit of developing pharmacotherapeutic strategies, which specifically address generalized avoidance.

The present study investigated the consequences of environmental enrichment on the impact of novelty and motivational properties of ethanol in spontaneously hypertensive rats (SHR), a validated model of attention deficit hyperactivity disorder (ADHD). This rat strain displays increased sensitivity to distinct classes of abused drugs, which makes it an interesting model for the study of the association between ADHD and drug abuse. Female SHR reared from weaning to adulthood in standard (SE) or enriched (EE) environment were tested on novelty-induced locomotion, saccharin consumption, ethanol consumption (forced and free-choice schedules) and ethanol-induced conditioned place preference (CPP). SHR reared in an EE showed reduced novelty-induced locomotion, consumed less saccharin and ethanol in a forced schedule and showed less ethanol preference in a free-choice schedule compared to SE rats. Moreover, EE rats did not develop CPP, whereas SE rats developed preference for ethanol (1.2g/kg). These results show that exposure to stimuli mimicking positive life experiences (environmental enrichment) induces persistent changes in the reward/motivational system of female SHR, suggesting an important role of the familiar environment during early stages of the neurodevelopment on the co-morbidity of ADHD and drug abuse.

Evidence are that inhibition of cyclooxygenase 2 (COX-2) enhances endocannabinoid signaling, indicating a crosstalk between these two eicosanoid pathways. Aspirin, a non-selective COX inhibitor, acetylates COX-2 with generation of a lipoxygenase (LOX) substrate, whose end product is the 15-epi-lipoxin A(4) (15-epi-LXA(4)), an aspirin-triggered lipoxin. Our objective was to investigate whether 15-epi-LXA(4) would potentiate in vivo effects of the endocannabinoid anandamide (AEA). Catalepsy was selected as a behavioral parameter and tested 5 min after AEA injection in all experiments. AEA induced dose-dependent (200 pmol/2 microl, i.c.v.) catalepsy. A sub-dose of AEA (10 pmol/2 microl, i.c.v.) was potentiated by aspirin (300 mg/kg, p.o.) via a 5-LOX-dependent step. The cataleptic effect induced by the interaction between sub-doses of 15-epi-LXA(4) (0.01 pmol/2 microl, i.c.v.) and AEA (10 pmol/2 microl, i.c.v.) was prevented by the cannabinoid CB(1) receptors antagonist SR141716A (1mg/kg, i.p.), but not by the antagonist of lipoxin ALX receptors Boc-2 (10 microg/kg, i.p.). While previous studies have shown that COX inhibition itself may enhance endocannabinoid effects, here we add another piece of evidence revealing that a LOX-derivative produced in consequence of COX-2 acetylation participates in this process.

The interaction between genes and environment seems to be relevant for the development of Attention Deficit/Hyperactivity Disorder (ADHD), one of the most prevalent childhood psychiatric diseases. The occurrence of ADHD is typically associated with poor academic performance, probably reflecting learning difficulties and/or cognitive impulsiveness. The inbred Spontaneously Hypertensive Rats (SHR) strain has often been considered as an animal model of ADHD, since they 'naturally' display the main ADHD symptomatology. Although pharmacological agents improve SHR's cognitive deficits, little is known about the involvement of environmental factors in SHR disabilities and to what extent 'protective' non-pharmacological factors may be considered as strategy for ADHD prevention. Here we investigated whether the rearing environment during neurodevelopment may counteract later cognitive deficits presented by adult SHR. Wistar (WIS) rats were also used to investigate whether the putative effects of environmental enrichment depend on a specific genetic background. The animals were reared in enriched environment (EE) or standard environment (SE) from the post-natal day 21 until 3 months of age (adulthood) and tested for cognitive and non-cognitive phenotypes. EE improved SHR's performance in open field habituation, water maze spatial reference, social and object recognition tasks, while non-cognitive traits, such as nociception and hypertension, were not affected by EE. Response of WIS rats was generally not affected by the present EE. These results show that the general low cognitive performance presented by SHR rats strongly depends on the rearing environment and they may suggest modifications of the familial environment as a putative preventive strategy to cope with ADHD.

The present study investigated the central effects of the eCB uptake/metabolism inhibitor AM404 and the phytocannabinoid cannabidiol (CBD) on the extinction of contextual fear memories in rats. Rats were conditioned and 24 h later subjected to three consecutive 9-min non-reinforced exposures to the conditioning context (extinction sessions, 24 h intervals). AM404 or CBD was injected i.c.v. 5 min before each extinction session and a 3-min drug-free test of contextual memory was performed 24 h after the last extinction session. AM404 (1.0 microg/microl, i.c.v.) and CBD (2.0 microg/microl, i.c.v.) facilitated extinction of contextual fear memory, with persistent effects. These responses were antagonized by the CB1-selective antagonist SR141716A (0.2 mg/kg, i.p.), but not by the TRPV1-selective antagonist capsazepine (5.0 microg/microl, i.c.v.). The effect of the anxiolytic drug Diazepam (DZP) on the extinction of contextual fear memory was also investigated. In contrast with the CBD and AM404 results, DZP induced a general reduction in the expression of conditioned freezing. Both AM404 and CBD induced anti-anxiogenic effect in the fear-potentiated plus-maze test, whereas DZP was anxiolytic in conditioned and unconditioned rats. In conclusion, CBD, a non-psychoactive phytocannabinoid could be an interesting pharmacological approach to reduce the anxiogenic effects of stress and promote the extinction of fear memories.

Facilitation of memory extinction by manipulation of the endocannabinoid (eCB) system has been recently studied in several paradigms. Our previous results pointed to facilitation of contextual fear memory extinction by a low dose of a cannabinoid agonist, with a suggestion of short-term effects. The aim of the present study was to further investigate the effects of cannabinoid drugs in the short- and long-term extinction of conditioned fear using an extended extinction protocol. Male Wistar rats were placed in a conditioning chamber and after 3min received a footshock (1.5mA, 1s). On the next day, they received i.p. drug treatment (WIN55212-2 0.25mg/kg, AM404 10mg/kg, SR141716A 1mg/kg) and were re-exposed to the conditioning chamber for 30min (extinction training). No-Extinction groups received the same drug treatment, but were exposed for 3min to the conditioning chamber. A drug-free test of contextual memory (3min) was performed 7 days later. The cannabinoid agonist WI55212-2 and the inhibitor of eCB metabolism/uptake AM404 facilitated short-term extinction. In addition, long-term effects induced by treatments with WIN55212 and AM404 were completely divergent to those of SR141716A treatment. The present results confirm and extend previous findings showing that the eCB system modulates short-term fear memory extinction with long-lasting consequences.

This study examined the analgesic effect of cocaine in Spontaneously Hypertensive Rats (SHR), which are considered a suitable model for the study of attention deficit hyperactivity disorder (ADHD), and in Wistar (WIS) rats of both sexes using the hot-plate test. In addition, we tested whether habituation to the unheated hot-plate apparatus, that "normalizes" the basal hypoalgesic phenotype of SHR, alters the subsequent cocaine-induced analgesia (CIA) in this strain. SHR of both sexes were hypoalgesic compared to WIS rats in the hot-plate test and showed higher sensitivity to CIA. Habituation to the unheated hot-plate reduced the basal nociceptive latency of SHR, suggesting cognitive/emotional modulation of pain in this strain, but did not alter the magnitude of CIA. The present study shows increased sensitivity to CIA in SHR, which may be related to abnormalities in the mesocorticolimbic dopaminergic system. Further studies using SHR strain may reveal new information on the neurobiological mechanisms underlying ADHD and its co-morbidity with drug addiction.

Converging evidence points to adolescence as a critical period for the onset of a wide range of neuropsychiatric disorders, including attention deficit hyperactivity disorder (ADHD) and drug abuse. Spontaneously hypertensive rats (SHR) are generally considered to be a suitable genetic model for the study of ADHD, since they display hyperactivity, impulsivity, poorly sustained attention, cognitive deficits and increased novelty seeking. Despite the high prevalence of ADHD among adolescents, studies using SHR have mainly been performed on adult animals. The aim of the present study was to evaluate the effect of acute intraperitoneal (i.p.) administration of the cannabinoid receptor agonist WIN 55,212-2 (0.25–2.5 mg/kg) on locomotor activity and anxiety-like behavior in male adolescent and adult SHR and Wistar rats using the open field and elevated plus-maze tests. WIN 55,212-2 at doses of 0.25 and 1.25 mg/kg (i.p.) selectively promoted locomotor stimulation in adolescent SHR in the open field, but not in adult SHR or Wistar rats (regardless of age). The effect of WIN 55,212-2 (0.25 mg/kg, i.p.) on locomotion of adolescent SHR was reversed by pretreatment with the selective cannabinoid CB 1 receptor antagonist AM 251 (0.25 mg/kg, i.p.). Moreover, although the present doses of WIN 55,212-2 had no effect on anxiety-related behaviors in any of the animal groups evaluated in the open field (central locomotion) or elevated plus-maze (time and entries in open arms), the highest dose of WIN 55,212-2 tested (2.5 mg/kg, i.p.) significantly decreased the number of closed-arm entries (an index of locomotor activity) of adolescent rats of both the Wistar and SHR strains in the elevated plus-maze. The present results indicate strain- and age-related effects of cannabinoids on locomotor activity in rats, extending the notion that adolescence and ADHD represent risk factors for the increased sensitivity to the effects of drugs.

The memory deficits induced by cannabinoid agonists have been found in several behavioral paradigms. Nevertheless, there is evidence that not all types of memory are impaired after cannabinoid administration. The aim of this study was to investigate whether the cannabinoid agonist WIN 55212-2 (WIN) is able to influence the acquisition of fear conditioning using tone and contextual versions. For tone-fear conditioning, male Wistar rats were placed in the conditioning chamber and after 3 min, a sound (CS) was presented for 10 s that terminated with a 1-s electric footshock (1.5 mA). For contextual-fear conditioning, a similar procedure was used but no sound was presented. Twenty-four hours after, the animals were re-exposed to the respective CS (tone or conditioning chamber) and the freezing behavior was registered. A subsequent experiment investigated a possible state-dependent effect of WIN by administering WIN or control solution 30 min before conditioning and before testing. WIN (2.5 and 5.0 mg/kg) administered i.p. 30 min before impaired contextual fear conditioning but did not modify the freezing behavior elicited by tone presentation. These animals did not show any state-dependent effects of WIN. Further, the impaired contextual conditioning was prevented by preadministration of SR141716A (1.0 mg/kg, i.p.) or SR147778 (1.0 mg/kg, i.p.), selective cannabinoid CB1 receptor antagonists. The present findings highlight that cannabinoid agonists effects are selective for the hippocampus-dependent aversive memories in rats. This effect appears to be related to the activation of CB1 cannabinoid receptors and confirms that cannabinoids might provide a novel approach for the treatment of unpleasant memories.

Evidence indicates that genetic, gender, and emotional/attentional aspects modulate the pain sensation. The present study examined the effect of swim-stress on nociceptive responses in Lewis (LEW) and spontaneously hypertensive (SHR) inbred rats (contrasting for anxiety-related behaviors), as well as in Wistar (WIS) rats of both sexes. Furthermore, we explored possible neurochemical mechanisms involved. In addition, we investigated whether habituation in the hot-plate apparatus could modify the hypoalgesic phenotype of SHR. Male and female LEW, SHR, and WIS rats were tested immediately before and 2 min after a 3-min swim in 15 degrees C water. The swim-stress induced analgesia in LEW and WIS, but not in SHR male rats. The same stressor induced analgesia in females of all three strains. In WIS female rats, the stress-induced analgesia (SIA) seems to involve, at least partially, a nonopioid N-methyl-d-aspartate (NMDA) analgesic system. Moreover, five brief exposures (90 s; 10-min intertrial interval) to the unheated hot-plate apparatus completely abolished the differences in basal hot-plate latencies observed in SHR compared with LEW and WIS strains. The present results demonstrate genetic and gender differences in nociceptive sensitivity and in the activation of endogenous analgesic systems in rats and highlight the influence of emotional reactivity. The SHR's hypoalgesic phenotype seems to involve central cognitive processes. Therefore, the LEW and SHR inbred strains may provide an important tool for study of the molecular bases underlying nociception and its modulation and the relationship with emotional/attentional processes.

The spontaneously hypertensive rat (SHR) is generally considered to be a suitable genetic model for the study of attention deficit hyperactivity disorder (ADHD), since it displays hyperactivity, impulsivity, poorly sustained attention, and deficits in learning and memory processes. Converging evidence suggests a primary role of disturbance in the dopaminergic neurotransmission in ADHD patients and in SHR, and in addition, some studies have also demonstrated alterations in adenosinergic neurotransmission in SHR. In the present study, adult female Wistar (WIS) and SHR rats received caffeine (1-10 mg/kg i.p.) 30 min before training, immediately after training, or 30 min before a test session in the spatial version of the Morris water maze. The effect of caffeine administration on WIS and SHR blood pressure was also measured. SHR needed significantly more trials in the training session to acquire the spatial information, but they displayed a similar profile to that of WIS rats in the test session (48 h later), demonstrating a selective deficit in spatial learning. Pre-training administration of caffeine (1-10 mg/kg i.p.) improved this spatial learning deficit in SHR, but did not alter the WIS performance. In contrast, post-training administration of caffeine (3 mg/kg i.p.) did not alter the SHR test performance, but increased memory retention in WIS rats. No dose of caffeine tested altered the mean blood pressure of WIS or SHR. These results demonstrate a selective spatial learning deficit in SHR which can be attenuated by pre-training administration of caffeine. In addition, the present findings indicate that the spatial learning deficit in SHR is not directly related to hypertension.

Over the last decade, adenosine receptors in the central nervous system have been implicated in the modulation of cognitive functions. Despite the general view that endogenous adenosine modulates cognition through the activation of adenosine A1 receptors, evidence is now emerging on a possible role of A2A receptors in learning and memory. The present review attempts to examine results reported in different studies using diverse animal models, to provide a comprehensive picture of the recent evidence of a relationship between adenosinergic function and memory deficits. The present data suggest that caffeine (a nonselective adenosine receptor antagonist) and selective adenosine A2A receptor antagonists can improve memory performance in rodents evaluated through different tasks. They might also afford protection against memory dysfunction elicited in experimental models of aging, Alzheimer's disease, Parkinson's disease and, in spontaneously hypertensive rats (SHR), a putative genetic model of attention deficit hyperactivity disorder (ADHD).