Caffeine and cannabinoid receptors modulate impulsive behavior in an animal model of attentional deficit and hyperactivity disorder.

Attention deficit and hyperactivity disorder (ADHD) is characterized by impaired levels of hyperactivity, impulsivity, and inattention. Adenosine and endocannabinoid systems tightly interact in the modulation of dopamine signaling, involved in the neurobiology of ADHD. In this study, we evaluated the modulating effects of the cannabinoid and adenosine systems in a tolerance to delay of reward task using the most widely used animal model of ADHD. Spontaneous Hypertensive Rats (SHR) and Wistar-Kyoto rats were treated chronically or acutely with caffeine, a non-selective adenosine receptor antagonist, or acutely with a cannabinoid agonist (WIN55212-2, WIN) or antagonist (AM251). Subsequently, animals were tested in the tolerance to delay of reward task, in which they had to choose between a small, but immediate, or a large, but delayed, reward. Treatment with WIN decreased, whereas treatment with AM251 increased the choices of the large reward, selectively in SHR rats, indicating a CB1 receptor-mediated increase in impulsive behavior. An acute pre-treatment with caffeine blocked WIN effects. Conversely, a chronic treatment with caffeine increased the impulsive phenotype and potentiated the WIN effects. The results indicate that both cannabinoid and adenosine receptors modulate impulsive behavior in SHR: the antagonism of cannabinoid receptors might be effective in reducing impulsive symptoms present in ADHD; in addition, caffeine showed the opposite effects on impulsive behavior depending on the length of treatment. These observations are of particular importance to consider when therapeutic manipulation of CB1 receptors is applied to ADHD patients who consume coffee.

Early signs of colonic inflammation, intestinal dysfunction, and olfactory impairments in the rotenone-induced mouse model of Parkinson's disease.

The factors that trigger the pathophysiology of Parkinson's disease (PD) are unknown. However, it is suggested that environmental factors, such as exposure to pesticides, play an important role, in addition to genetic predisposition and aging. Early signs of PD can appear in the gastrointestinal (GI) tract and in the olfactory system, preceding the onset of motor impairments by many years. The present study assessed the effects of oral rotenone administration (30 mg/kg) in inducing GI and olfactory dysfunctions associated with PD in mice. Here we show that rotenone transiently increased myeloperoxidase activity within 24 h of administration. Leucocyte infiltration in the colon, associated with histological damage and disrupted GI motility, were observed following treatment with rotenone for 7 days. Moreover, 7 days of treatment with rotenone disrupted olfactory discrimination in mice without affecting social recognition ability. The presence of specific deficits in olfactory function occurred with a concomitant decrease in tyrosine hydroxylase-positive neurons and an increase in serotonin (5-hydroxytryptamine) turnover in the olfactory bulb. These findings suggest that in Swiss mice, exposure to rotenone induces GI and olfactory dysfunction involving immunological and neurotransmitter alterations, similar to early signs of PD. This provides further evidence for the involvement of the gut-brain axis in PD.

Anti-inflammatory lipoxin A4 is an endogenous allosteric enhancer of CB1 cannabinoid receptor.

Allosteric modulation of G-protein-coupled receptors represents a key goal of current pharmacology. In particular, endogenous allosteric modulators might represent important targets of interventions aimed at maximizing therapeutic efficacy and reducing side effects of drugs. Here we show that the anti-inflammatory lipid lipoxin A(4) is an endogenous allosteric enhancer of the CB(1) cannabinoid receptor. Lipoxin A(4) was detected in brain tissues, did not compete for the orthosteric binding site of the CB(1) receptor (vs. (3)H-SR141716A), and did not alter endocannabinoid metabolism (as opposed to URB597 and MAFP), but it enhanced affinity of anandamide at the CB1 receptor, thereby potentiating the effects of this endocannabinoid both in vitro and in vivo. In addition, lipoxin A(4) displayed a CB(1) receptor-dependent protective effect against ß-amyloid (1-40)-induced spatial memory impairment in mice. The discovery of lipoxins as a class of endogenous allosteric modulators of CB(1) receptors may foster the therapeutic exploitation of the endocannabinoid system, in particular for the treatment of neurodegenerative disorders.

Cellular prion protein is present in dopaminergic neurons and modulates the dopaminergic system.

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.

PTSD-like memory generated through enhanced noradrenergic activity is mitigated by a dual step pharmacological intervention targeting its reconsolidation.

BACKGROUND: Traumatic memories have been resilient to therapeutic approaches targeting their permanent attenuation. One of the potentially promising pharmacological strategies under investigation is the search for safe reconsolidation blockers. However, preclinical studies focusing on this matter have scarcely addressed abnormal aversive memories and related outcomes. METHODS: By mimicking the enhanced noradrenergic activity reported after traumatic events in humans, here we sought to generate a suitable condition to establish whether some clinically approved drugs able to disrupt the reconsolidation of conditioned fear memories in rodents would still be effective. RESULTS: We report that the α2-adrenoceptor antagonist yohimbine was able to induce an inability to restrict behavioral (fear) and cardiovascular (increased systolic blood pressure) responses to the paired context when administered immediately after acquisition, but not 6h later, indicating the formation of a generalized fear memory, which endured for over 29 days and was less susceptible to suppression by extinction. It was also resistant to reconsolidation disruption by the α2-adrenoceptor agonist clonidine or cannabidiol, the major non-psychotomimetic component of Cannabis sativa. Since signaling at N-methyl-D-aspartate (NMDA) receptors is important for memory labilization and because a dysfunctional memory may be less labile than is necessary to trigger reconsolidation on its brief retrieval and reactivation, we then investigated and demonstrated that pre-retrieval administration of the partial NMDA agonist D-cycloserine allowed the disrupting effects of clonidine and cannabidiol on reconsolidation. CONCLUSIONS: These findings highlight the effectiveness of a dual-step pharmacological intervention to mitigate an aberrant and enduring aversive memory similar to that underlying the post-traumatic stress disorder.

Interactions of Noradrenergic, Glucocorticoid and Endocannabinoid Systems Intensify and Generalize Fear Memory Traces.

Systemic administration of drugs that activate the noradrenergic or glucocorticoid system potentiates aversive memory consolidation and reconsolidation. The opposite happens with the stimulation of endocannabinoid signaling under certain conditions. An unbalance of these interacting neurotransmitters can lead to the formation and maintenance of traumatic memories, whose strength and specificity attributes are often maladaptive. Here we aimed to investigate whether originally low-intensity and precise contextual fear memories would turn similar to traumatic ones in rats systemically administered with adrenaline, corticosterone, and/or the cannabinoid type-1 receptor antagonist/inverse agonist AM251 during consolidation or reconsolidation. The high dose of each pharmacological agent evaluated significantly increased freezing times at test in the conditioning context one and nine days later when given alone post-acquisition or post-retrieval. Their respective low dose produced no relative changes when given separately, but co-treatment of adrenaline with corticosterone or AM251 and the three drugs combined, but not corticosterone with AM251, produced results equivalent to those mentioned initially. Neither the high nor the low dose of adrenaline, corticosterone, or AM251 altered freezing times at test in a novel, neutral context two and ten days later. In contrast, animals receiving the association of their low dose exhibited significantly higher freezing times than controls. Together, the results indicate that newly acquired and destabilized threat memory traces become more intense and generalized after a combined interference acting synergistically and mimicking that reported in patients presenting stress-related psychiatric conditions.

From an Alternative Medicine to a New Treatment for Refractory Epilepsies: Can Cannabidiol Follow the Same Path to Treat Neuropsychiatric Disorders?

Although cannabis has been known for ages as an "alternative medicine" to provide relief from seizures, pain, anxiety, and inflammation, there had always been a limited scientific review to prove and establish its use in clinics. Early studies carried out by Carlini's group in Brazil suggested that cannabidiol (CBD), a non-psychotropic phytocannabinoid present in Cannabis sativa, has anticonvulsant properties in animal models and reduced seizure frequency in limited human trials. Over the past few years, the potential use of cannabis extract in refractory epilepsy, including childhood epilepsies such as Dravet's syndrome and Lennox-Gastaut Syndrome, has opened a new era of treating epileptic patients. Thus, a considerable number of pre-clinical and clinical studies have provided strong evidence that phytocannabinoids has anticonvulsant properties, as well as being promising in the treatment of different neuropsychiatric disorders, such as depression, anxiety, post-traumatic stress disorder (PTSD), addiction, neurodegenerative disorders and autism spectrum disorder (ASD). Given the advances of cannabinoids, especially CBD, in the treatment of epilepsy, would the same expectation regarding the treatment of other neuropsychiatric disorders be possible? The present review highlights some contributions from Brazilian researchers and other studies reported elsewhere on the history, pre-clinical and clinical data underlying the use of cannabinoids for the already widespread treatment of refractory epilepsies and the possibility of use in the treatment of some neuropsychiatric disorders.

Adenosine receptor antagonists improve short-term object-recognition ability of spontaneously hypertensive rats: a rodent model of attention-deficit hyperactivity disorder.

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.

Connecting TNF-alpha signaling pathways to iNOS expression in a mouse model of Alzheimer's disease: relevance for the behavioral and synaptic deficits induced by amyloid beta protein.

Increased brain deposition of amyloid beta protein (Abeta) and cognitive deficits are classical signals of Alzheimer's disease (AD) that have been highly associated with inflammatory alterations. The present work was designed to determine the correlation between tumor necrosis factor-alpha (TNF-alpha)-related signaling pathways and inducible nitric oxide synthase (iNOS) expression in a mouse model of AD, by means of both in vivo and in vitro approaches. The intracerebroventricular injection of Abeta(1-40) in mice resulted in marked deficits of learning and memory, according to assessment in the water maze paradigm. This cognition impairment seems to be related to synapse dysfunction and glial cell activation. The pharmacological blockage of either TNF-alpha or iNOS reduced the cognitive deficit evoked by Abeta(1-40) in mice. Similar results were obtained in TNF-alpha receptor 1 and iNOS knock-out mice. Abeta(1-40) administration induced an increase in TNF-alpha expression and oxidative alterations in prefrontal cortex and hippocampus. Likewise, Abeta(1-40) led to activation of both JNK (c-Jun-NH2-terminal kinase)/c-Jun and nuclear factor-kappaB, resulting in iNOS upregulation in both brain structures. The anti-TNF-alpha antibody reduced all of the molecular and biochemical alterations promoted by Abeta(1-40). These results provide new insights in mouse models of AD, revealing TNF-alpha and iNOS as central mediators of Abeta action. These pathways might be targeted for AD drug development.

Short- and long-term effects of cannabinoids on the extinction of contextual fear memory in rats.

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.

Facilitation of contextual fear memory extinction and anti-anxiogenic effects of AM404 and cannabidiol in conditioned rats.

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.

Cannabidiol as a Therapeutic Alternative for Post-traumatic Stress Disorder: From Bench Research to Confirmation in Human Trials.

Post-traumatic stress disorder (PTSD) is characterized by poor adaptation to a traumatic experience. This disorder affects approximately 10% of people at some point in life. Current pharmacological therapies for PTSD have been shown to be inefficient and produce considerable side effects. Since the discovery of the involvement of the endocannabinoid (eCB) system in emotional memory processing, pharmacological manipulation of eCB signaling has become a therapeutic possibility for the treatment of PTSD. Cannabidiol (CBD), a phytocannabinoid constituent of Cannabis sativa without the psychoactive effects of Δ9-tetrahydrocannabinol, has gained particular attention. Preclinical studies in different rodent behavioral models have shown that CBD can both facilitate the extinction of aversive memories and block their reconsolidation, possibly through potentialization of the eCB system. These results, combined with the currently available pharmacological treatments for PTSD being limited, necessitated testing CBD use with the same therapeutic purpose in humans as well. Indeed, as observed in rodents, recent studies have confirmed the ability of CBD to alter important aspects of aversive memories in humans and promote significant improvements in the symptomatology of PTSD. The goal of this review was to highlight the potential of CBD as a treatment for disorders related to inappropriate retention of aversive memories, by assessing evidence from preclinical to human experimental studies.

Effects of Cannabinoid Drugs on Aversive or Rewarding Drug-Associated Memory Extinction and Reconsolidation.

Posttraumatic stress and drug use disorders may stem from aberrant memory formation. As the endocannabinoid (eCB) system has a pivotal role in emotional memory processing and related synaptic plasticity, here we seek to review and discuss accumulating evidence on how and where in the brain interventions targeting the eCB system would attenuate outcomes associated with traumatic events and/or drug addiction through memory extinction facilitation or reconsolidation disruption. Currently available data from mouse, rat, monkey and healthy human studies investigating the effects of cannabinoid drugs on extinction and reconsolidation of aversive memories are more consistent than those related to rewarding drug-associated memories. Interventions able to attenuate aversive memories by extinction facilitation or reconsolidation disruption have boosted the anandamide-induced activation of cannabinoid type-1 (CB1) receptors. A still limited number of studies report that CB1 receptor activation could also be effective in facilitating the extinction or disrupting the reconsolidation of rewarding drug-associated memories. The reinstatement of extinguished drug memories (relapse) is reduced by CB1 receptor antagonism. The cannabidiol has shown to be effective in any of the aforementioned cases, albeit its mechanism of action is not fully understood. Brain areas in which cannabinoid drugs induce these effects include the prefrontal cortex, amygdala, hippocampus, and/or nucleus accumbens. The potential role of 2-arachidonoylglycerol (2-AG) and cannabinoid type-2 (CB2) receptors in emotional memory extinction and reconsolidation is currently under investigation. Overall, preclinical data support a closer look into certain cannabinoid drugs owing to their safety and potential therapeutic value against stress-related and drug use disorders.

Zinc attenuates malathion-induced depressant-like behavior and confers neuroprotection in the rat brain.

Malathion is an organophosphate widely used as an insecticide in agriculture and in public health programs, causing risk to human health. As was recently reported, malathion induces depressant-like behavior and oxidative damage to the brain of rodents. Given the relevance of searching for neuroprotective agents against such damage, this study was therefore undertaken to investigate the neuroprotective potential of zinc in dealing with malathion-related toxicity. Female Wistar rats were exposed to malathion (50 and 100 mg/kg, ip) and/or zinc chloride (ZnCl2; 5 mg/kg, ip) for 3 days. Malathion produced a depressant-like effect, observed by the increased immobility time in the forced swimming test (FST), without affecting total locomotor activity and rearing in the open-field. However, malathion administered at 50 mg/kg reduced the central time in the arena and at the dose of 100 mg/kg reduced the central locomotion. These effects were completely reversed by ZnCl2. Exposure to malathion (50 mg/kg, ip) and/or ZnCl2 did not affect AChE activity in the hippocampus, cerebral cortex, and blood. Malathion (50 mg/kg, ip) alone caused some harmful effects, such as (1) an increase in lipid peroxidation and a reduction of glutathione peroxidase activity in the cerebral cortex, (2) reduction of glutathione reductase activity in the hippocampus, and (3) changes in the structure of chromatin in the dentate gyrus, all effects attenuated by ZnCl2. In conclusion, these results clearly show that zinc administration is able to attenuate some neurochemical, morphological, and behavioral effects induced by malathion, notably the malathion-induced depressant-like effect in the FST.

Differential susceptibility following beta-amyloid peptide-(1-40) administration in C57BL/6 and Swiss albino mice: Evidence for a dissociation between cognitive deficits and the glutathione system response.

Considerable evidence supports the role of oxidative stress in the pathogenesis of Alzheimer's disease (AD). Previous studies suggest that the central nervous system (CNS) administration of beta-amyloid peptide, the major constituent of senile plaque in AD, induces oxidative stress in rodents which may contribute to the learning and memory deficits verified in the beta-amyloid model of AD. In the present study, we compared the effects of a single intracerebroventricular (i.c.v.) injection of aggregated beta-amyloid peptide-(1-40) (Abeta(1-40)) (400pmol/mouse) on spatial learning and memory performance, synaptic density and the glutathione (GSH)-dependent antioxidant status in adult male C57BL/6 and Swiss albino mice. Seven days after Abeta(1-40) administration, C57BL/6 and Swiss mice presented similar spatial learning and memory impairments, as evaluated in the water maze task, although these impairments were not found in Abeta(40-1)-treated mice. Moreover, a similar decline of synaptophysin levels was observed in the hippocampus (HC) and prefrontal cortex (PFC) of both Swiss and C57BL/6 mice treated with Abeta(1-40), which suggests synaptic loss. C57BL/6 mice presented lower levels of glutathione-related antioxidant defences (total glutathione (GSH-t) levels, glutathione peroxidase (GPx) and glutathione reductase (GR) activity) in the HC and PFC in comparison to Swiss mice. Despite the reduced basal GSH-dependent antioxidant defences observed in C57BL/6 mice, Abeta(1-40) administration induced significant alterations in the brain antioxidant parameters only in Swiss mice, decreasing GSH-t levels and increasing GPx and GR activity in the HC and PFC 24h after treatment. These results indicate strain differences in the susceptibility to Abeta(1-40)-induced changes in the GSH-dependent antioxidant defences in mice, which should be taken into account in further studies using the Abeta model of AD in mice. In addition, the present findings suggest that the spatial learning and memory deficits induced by beta-amyloid peptides in rodents may not be entirely related to glutathione-dependent antioxidant response.

Increased sensitivity to cocaine-induced analgesia in Spontaneously Hypertensive Rats (SHR).

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.

Increased sensitivity of adolescent spontaneously hypertensive rats, an animal model of attention deficit hyperactivity disorder, to the locomotor stimulation induced by the cannabinoid receptor agonist WIN 55,212-2.

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 CB1 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.

Antioxidant responses and lipid peroxidation following intranasal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in rats: increased susceptibility of olfactory bulb.

We evaluated an alternative method to investigate a possible involvement of environmental toxins in the pathology of Parkinson's disease (PD). There is considerable evidence supporting the role of oxidative stress in the toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin largely used to modeling PD in primates and rodents. We have recently demonstrated that rats treated with intranasal (i.n.) infusion of MPTP suffer from progressive signs of PD that are correlated with time-dependent degeneration in dopaminergic neurons. In the present study, we investigated the time-dependent (2 h to 7 days) effect of a single i.n. administration of MPTP (0.1 mg/nostril) on the glutathione-related antioxidant status and lipid peroxidation (TBARS) in the adult Wistar rat brain. The effects were more pronounced in the olfactory bulb at 6 h after i.n. MPTP administration, as indicated by an increase in TBARS and total glutathione (GSH-t) levels, and also in the gamma-glutamyl transpeptidase (GGT) activity. Increased levels of TBARS, GSH-t and GGT activity were also observed at 6 h post-MPTP infusion in some structures (e.g. striatum, hippocampus and prefrontal cortex). No difference regarding glutathione reductase activity was observed in any of the brain structures analyzed, while a marked decrease in glutathione peroxidase activity was specifically observed in the substantia nigra 7 days after MPTP treatment. These results demonstrate that a single i.n. infusion of MPTP in rats induces significant alterations in the brain antioxidant status and lipid peroxidation, reinforcing the notion that the olfactory system represents a particularly sensitive route for the transport of neurotoxins into the central nervous system that may be related to the etiology of PD.

Angiotensin II type 1/adenosine A 2A receptor oligomers: a novel target for tardive dyskinesia.

Tardive dyskinesia (TD) is a serious motor side effect that may appear after long-term treatment with neuroleptics and mostly mediated by dopamine D2 receptors (D2Rs). Striatal D2R functioning may be finely regulated by either adenosine A2A receptor (A2AR) or angiotensin receptor type 1 (AT1R) through putative receptor heteromers. Here, we examined whether A2AR and AT1R may oligomerize in the striatum to synergistically modulate dopaminergic transmission. First, by using bioluminescence resonance energy transfer, we demonstrated a physical AT1R-A2AR interaction in cultured cells. Interestingly, by protein-protein docking and molecular dynamics simulations, we described that a stable heterotetrameric interaction may exist between AT1R and A2AR bound to antagonists (i.e. losartan and istradefylline, respectively). Accordingly, we subsequently ascertained the existence of AT1R/A2AR heteromers in the striatum by proximity ligation in situ assay. Finally, we took advantage of a TD animal model, namely the reserpine-induced vacuous chewing movement (VCM), to evaluate a novel multimodal pharmacological TD treatment approach based on targeting the AT1R/A2AR complex. Thus, reserpinized mice were co-treated with sub-effective losartan and istradefylline doses, which prompted a synergistic reduction in VCM. Overall, our results demonstrated the existence of striatal AT1R/A2AR oligomers with potential usefulness for the therapeutic management of TD.

Blockade of hippocampal bradykinin B1 receptors improves spatial learning and memory deficits in middle-aged rats.

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.