Leyre Urigüen

Impaired action of anxiolytic drugs in mice deficient in cannabinoid CB1 receptors.

The role of cannabinoid CB(1) receptors in the action of anxiolytics was examined. Deletion of CB(1) receptors resulted in increased anxiety-like behaviours in light/dark box, elevated plus maze and social interaction tests. Mutant mice presented basal low corticosterone concentrations and low proopiomelanocortin gene expression in the anterior lobe of the pituitary gland compared to wild-type mice. Ten minutes of restraint stress resulted in a twofold increase in corticosterone concentrations in the plasma of mutant mice, compared to wild-type mice. Bromazepam (50 or 100 microg/kg) markedly increased the time spent in light area in wild-type animals, though both doses were without effect in mutant mice. Administration of buspirone (1 or 2 mg/kg) produced anxiolytic effects in wild-type mice. In contrast, only the highest dose of buspirone had anxiolytic results in mutant mice. Our findings reveal that CB(1) receptors are involved in the regulation of emotional responses, and play a pivotal role in the action mechanism of anxiolytics. They suggest that alterations in the functional activity of the CB(1) receptor may be related to the emergence of anxiety disorders, and may affect treatment with anxiolytics.

Immunodensity and mRNA expression of A2A adenosine, D2 dopamine, and CB1 cannabinoid receptors in postmortem frontal cortex of subjects with schizophrenia: effect of antipsychotic treatment

RationaleDopamine D2 receptors are the main target of antipsychotic drugs. In the brain, D2 receptors coexpress with adenosine A2A and CB1 cannabinoid receptors, leading to functional interactions.ObjectivesThe protein and messenger RNA (mRNA) contents of A2A, D2, and CB1 receptors were quantified in postmortem prefrontal cortex of subjects with schizophrenia.Materials and methodsThe study was performed in subjects suffering schizophrenia (n = 31) who mainly died by suicide, matched with non-schizophrenia suicide victims (n = 13) and non-suicide controls (n = 33). The density of receptor proteins was evaluated by immunodetection techniques, and their relative mRNA expression was quantified by quantitative real-time polymerase chain reaction.ResultsIn schizophrenia, the densities of A2A (90 ± 6%, n = 24) and D2-like receptors (95 ± 5%, n = 22) did not differ from those in controls (100%). Antipsychotic treatment did not induce changes in the protein expression. In contrast, the immunodensity of CB1 receptors was significantly decreased (71 ± 7%, n = 11; p < 0.05) in antipsychotic-treated subjects with schizophrenia but not in drug-free subjects (104 ± 13%, n = 11). The relative mRNA amounts encoding for A2A, D2, and CB1 receptors were similar in brains of drug-free, antipsychotic-treated subjects with schizophrenia and controls.ConclusionsThe findings suggest that antipsychotics induce down-regulation of CB1 receptors in brain. Since A2A, D2, and CB1 receptors coexpress on brain GABAergic neurons and reductions in markers of GABA neurotransmission have been identified in schizophrenia, a lower density of CB1 receptor induced by antipsychotics could represent an adaptative mechanism that reduces the endocannabinoid-mediated suppression of GABA release, contributing to the normalization of cognitive functions in the disorder.

Time course of opioid and cannabinoid gene transcription alterations induced by repeated administration with fluoxetine in the rat brain.

This study examined the time course effects (8, 16 and 31 days) of fluoxetine administration (1 mg/kg, p.o./day) on serotonin transporter (5-HTT), opioid, tyrosine hydroxylase (TH) and cannabinoid CB1 receptor gene expressions in selected regions of the rat brain. Treatment with fluoxetine progressively decreased (35-55%) 5-HTT gene expression in dorsal raphe nucleus at 8, 16 and 31 days. The results revealed that fluoxetine administration decreased (30%) proenkephalin gene expression in nucleus accumbens shell (AcbS) and caudate-putamen (CPu) (31 days) but was without effect in nucleus accumbens core AcbC. A pronounced and time related decrease (25-65%) in prodynorphin gene expression was detected in AcbC, AcbS, CPu, hypothalamic supraoptic and paraventricular nuclei at all time points as well as in proopiomelanocortin gene expression (20-30%) in the arcuate nucleus (ARC) of the hypothalamus. On days 16 and 31, tyrosine hydroxylase gene expression in ventral tegmental area and substantia nigra and cannabinoid CB1 receptor gene expression in the CPu decreased (approximately 45-50% from vehicle). In conclusion, fluoxetine by inhibiting the reuptake of serotonin produced pronounced and time related alterations in genes involved in the regulation of emotional behaviour, suggesting that these neuroplastic changes may be involved, at least in part, in the clinical efficacy of this drug in neuropsychiatric disorders.

Role of endocannabinoid system in mental diseases

In the last decade, a large number of studies using Δ9-tetrahydrocannabinol (THC), the main active principle derivative of the marijuana plant, or cannabinoid synthetic derivatives have substantially contributed to advance the understanding of the pharmacology and neurobiological mechanisms produced by cannabinoid receptor activation.Cannabis has been historically used to relieve some of the symptoms associated with central nervous system disorders. Nowadays, there are anecdotal evidences for the use of cannabis in many patients suffering from multiple sclerosis or chronic pain. Following the historical reports on the use of cannabis for medicinal purposes, recent research has highlighted the potential of cannabinoids to treat a wide variety of clinical disorders. Some of these disorders that are being investigated are pain, motor dysfunctions, or psychiatric illness. On the other hand, cannabis abuse has been related to several psychiatric disorders such as dependence, anxiety, depression, cognitive impairment, and psychosis.Considering that cannabis or cannabinoid pharmaceutical preparations may no longer be exclusively recreational drugs but may also present potential therapeutic uses, it has become of great interest to analyze the neurobiological and behavioral consequences of their administration.This review attempts to link current understanding of the basic neurobiology of the endocannabi-noid system to novel opportunities for therapeutic intervention and its effects on the central nervous system.

Kappa- and delta-opioid receptor functional activities are increased in the caudate putamen of cannabinoid CB1 receptor knockout mice.

The purpose of this study was to examine the functional interaction between endogenous opioid and cannabinoid receptor systems in the caudate putamen and nucleus accumbens. We therefore examined by autoradiography the functional activity and density of µ‐, κ‐ and δ‐opioid receptors in both brain regions of cannabinoid CB1 receptor knockout mice. Functional activity was estimated by measuring agonist‐stimulated [35S]GTPγS binding. Results showed that deletion of the CB1 cannabinoid receptor markedly increased κ‐opioid (50%) and δ‐opioid (42%) receptor activities whereas no differences were found in µ‐opioid receptor in the caudate putamen. In contrast, binding autoradiography showed a similar density of µ‐, κ‐ and δ‐opioid receptors between mutant and wild‐type mice. No differences were found in densities or activities of µ‐, κ‐ and δ‐opioid receptors between mutant and wild‐type mice in the nucleus accumbens. Taken together, our results revealed that deletion of CB1 cannabinoid receptors produced a pronounced increase in the activity of κ‐ and δ‐opioid receptors in the caudate putamen. This endogenous interaction between opioid and cannabinoid receptors may be relevant to further understand a variety of neuroadaptative processes involving the participation of opioid receptors, such as motor behaviour, emotional responses and drug dependence.

Regulation of munc18-1 and syntaxin-1A interactive partners in schizophrenia prefrontal cortex: down-regulation of munc18-1a isoform and 75 kDa SNARE complex after antipsychotic treatment

Munc18-1 and syntaxin-1 are crucial interacting molecules for synaptic membrane fusion and neurotransmitter release. Contrasting abnormalities of several proteins of the exocytotic machinery, including the formation of SNARE (synaptobrevin, SNAP-25 and syntaxin-1) complexes, have been reported in schizophrenia. This study quantified in the dorsolateral prefrontal cortex (PFC, Brodmann area 9) the immunocontent of munc18-1a/b isoforms, syntaxin-1A, other presynaptic proteins (synaptotagmin, synaptophysin), and SNARE complexes, as well as the effects of psychoactive drug exposure, in schizophrenia (SZ, n=24), non-schizophrenia suicide (SD, n=13) and major depression (MD, n=15) subjects compared to matched controls (n=39). SZ was associated with normal expression of munc18-1a/b and increased syntaxin-1A (+44%). The presence of antipsychotic drugs reduced the basal content of munc18-1a isoform (-23%) and synaptobrevin (-32%), and modestly reduced that of up-regulated syntaxin-1A (-16%). Munc18-1a and syntaxin-1A protein expression correlated positively in controls but showed a markedly opposite pattern in SZ, regardless of antipsychotic treatment. Thus, the ratio of syntaxin-1A to munc18-1a showed a net increase in SZ (+53/114%). The SNARE complex (75 kDa) was found unaltered in antipsychotic-free and reduced (-28%) in antipsychotic-treated SZ subjects. None of these abnormalities were observed in SD and MD subjects, unexposed or exposed to psychoactive drugs. The results reveal some exocytotic dysfunctions in SZ that are probably related to an imbalance of the interaction between munc18-1a and SNARE (mainly syntaxin-1A) complex. Moreover, antipsychotic drug treatment is associated with lower content of key proteins of the exocytotic machinery, which could result in a destabilization/impairment of neurosecretion.

Pretreatment with Resveratrol Prevents Neuronal Injury and Cognitive Deficits Induced by Perinatal Hypoxia-Ischemia in Rats

Despite advances in neonatal care, hypoxic-ischemic brain injury is still a serious clinical problem, which is responsible for many cases of perinatal mortality, cerebral palsy, motor impairment and cognitive deficits. Resveratrol, a natural polyphenol with important anti-oxidant and anti-inflammatory properties, is present in grapevines, peanuts and pomegranates. The aim of the present work was to evaluate the possible neuroprotective effect of resveratrol when administered before or immediately after a hypoxic-ischemic brain event in neonatal rats by analyzing brain damage, the mitochondrial status and long-term cognitive impairment. Our results indicate that pretreatment with resveratrol protects against brain damage, reducing infarct volume, preserving myelination and minimizing the astroglial reactive response. Moreover its neuroprotective effect was found to be long lasting, as behavioral outcomes were significantly improved at adulthood. We speculate that one of the mechanisms for this neuroprotection may be related to the maintenance of the mitochondrial inner membrane integrity and potential, and to the reduction of reactive oxygen species. Curiously, none of these protective features was observed when resveratrol was administered immediately after hypoxia-ischemia.

Decreased GABAA and GABAB receptor functional activity in cannabinoid CB1 receptor knockout mice

The interaction between brain GABAergic and endocannabinoid systems was evaluated by examining the quantitative and functional status of GABAergic receptors in cannabinoid CB1 receptor knockout (CB1 -/-) mice. To this aim, GABAA ([3H]-Muscimol binding assay), GABAB (baclofen-stimulated [35S]-GTPγS binding assay), GABAAα1, GABAAα2 and GABAAγ2 receptors gene expression (real-time reverse transcriptase polymerase chain reaction [PCR]) were carried out in CB1 -/- and wild-type mice (CB1 +/+). [3H]-Muscimol binding assays revealed significant reduction in the density of GABAA receptors in CA2 (30%) and DG (28%) of the hippocampus, thalamus (40%), cingulate (28%) and motor cortex (35%) of CB1 -/- mice. Functional activity of metabotropic GABAB receptors was measured by evaluating the ability of GABAB agonist baclofen to stimulate [35S]-GTPγS binding. The results showed significant reduced [35S]-GTPγS binding in CA1 (61%), CA3 (51%) and DG (60%) of CB1 -/- mice compared with CB1 +/+ mice. Real-time reverse transcriptase PCR was carried out for evaluating gene expression of α1, α2 and γ2 subunits of GABAA receptor in the amygdala. The results showed significant reduced GABAAα1 (50%) and GABAAα2 (40%) receptor subunits gene expression in the amygdala of CB1 -/- mice. No difference was observed in GABAAγ2 receptor subunit gene expression. This study provides strong evidence of the involvement of CB1 receptors in the control of GABAergic responses mediated by GABAA and GABAB receptors, and suggests a possible role of the endocannabinoid system in the regulation of anxiety-related disorders.

Antidepressant-like properties of three new α2-adrenoceptor antagonists.

Evidence suggests that depression is associated with an increase in the high-affinity conformation of the α2-adrenoceptors in human brain. Such enhanced α2-adrenoceptor activity could explain the deficit in central noradrenergic transmission described in the aetiology of depression. Thus, administration of α2-adrenoceptor antagonists augments noradrenaline levels and provides an effective therapeutic approach for the treatment of depressive disorders. In previous studies, we have characterized three new synthesized guanidine and 2-aminoimidazoline aromatic derivatives (8b, 17b and 20b) as α2-adrenoceptor antagonists that are able to increase extracellular concentration of noradrenaline in rat brain. The purpose of the present study was to evaluate the in vivo antidepressant-like properties of these three new α2-adrenoceptor antagonists. For that aim, compounds were tested on the tail suspension test (TST) and forced swim test (FST), two classically widely-used behavioural paradigms for the evaluation of antidepressant-like activity. Compound 8b significantly reduced the immobility time at 10, 20 and 40 mg/kg doses in both TST and FST. Compound 17b reduced the immobility time at 40 mg/kg in both TST and FST. Compound 20b showed a significant decrease in the immobility time at 20 mg/kg in the TST. As drugs of reference, fluoxetine induced a significant antidepressant-like effect in both TST and FST, while mirtazapine induced a significant antidepressant-like effect only in the FST. Additionally, none of the tested compounds increased locomotor activity or displayed anxiolytic-like properties. These results suggest that these new synthesized α2-adrenoceptor antagonists may be useful as potential antidepressant drugs.

Activation of the orphan receptor GPR55 by lysophosphatidylinositol promotes metastasis in triple-negative breast cancer.

The orphan G protein-coupled receptor GPR55 has been directly or indirectly related to basic alterations that drive malignant growth: uncontrolled cancer cell proliferation, sustained angiogenesis, and cancer cell adhesion and migration. However, little is known about the involvement of this receptor in metastasis. Here, we show that elevated GPR55 expression in human tumors is associated with the aggressive basal/triple-negative breast cancer population, higher probability to develop metastases, and therefore poor patient prognosis. Activation of GPR55 by its proposed endogenous ligand lysophosphatidylinositol confers pro-invasive features on breast cancer cells both in vitro and in vivo. Specifically, this effect is elicited by coupling to Gq/11 heterotrimeric proteins and the subsequent activation, through ERK, of the transcription factor ETV4/PEA3. Together, these data show that GPR55 promotes breast cancer metastasis, and supports the notion that this orphan receptor may constitute a new therapeutic target and potential biomarker in the highly aggressive triple-negative subtype.