Alvaro Llorente-Berzal

Species differences in cannabinoid receptor 2 (CNR2 gene): identification of novel human and rodent CB2 isoforms, differential tissue expression, and regulation by cannabinoid receptor ligands

Cannabinoids, endocannabinoids and marijuana activate two well‐characterized cannabinoid receptors (CB‐Rs), CB1‐Rs and CB2‐Rs. The expression of CB1‐Rs in the brain and periphery has been well studied, but neuronal CB2‐Rs have received much less attention than CB1‐Rs. Many studies have now identified and characterized functional glial and neuronal CB2‐Rs in the central nervous system. However, many features of CB2‐R gene structure, regulation and variation remain poorly characterized in comparison with the CB1‐R. In this study, we report on the discovery of a novel human CB2 gene promoter transcribing testis (CB2A) isoform with starting exon located ca 45 kb upstream from the previously identified promoter transcribing the spleen isoform (CB2B). The 5′ exons of both CB2 isoforms are untranslated 5′UTRs and alternatively spliced to the major protein coding exon of the CB2 gene. CB2A is expressed higher in testis and brain than CB2B that is expressed higher in other peripheral tissues than CB2A. Species comparison found that the CB2 gene of human, rat and mouse genomes deviated in their gene structures and isoform expression patterns. mCB2A expression was increased significantly in the cerebellum of mice treated with the CB‐R mixed agonist, WIN55212‐2. These results provide much improved information about CB2 gene structure and its human and rodent variants that should be considered in developing CB2‐R‐based therapeutic agents.

Gender-dependent cellular and biochemical effects of maternal deprivation on the hippocampus of neonatal rats: A possible role for the endocannabinoid system

Adult animals submitted to a single prolonged episode of maternal deprivation (MD) [24 h, postnatal days (PND) 9–10] show behavioral alterations that resemble specific symptoms of schizophrenia. These behavioral impairments may be related to neuronal loss in the hippocampus triggered by elevated glucocorticoids. Furthermore, our previous data suggested functional relationships between MD stress and the endocannabinoid system. In this study, we addressed the effects of MD on hippocampal glial cells and the possible relationship with changes in plasma corticosterone (CORT) levels. In addition, we investigated the putative involvement of the endocannabinoid system by evaluating (a) the effects of MD on hippocampal levels of endocannabinoids (b) The modulation of MD effects by two inhibitors of endocannabinoids inactivation, the fatty acid amide hydrolase inhibitor N‐arachidonoyl‐serotonin (AA‐5‐HT), and the endocannabinoid reuptake inhibitor, OMDM‐2. Drug treatments were administered once daily from PND 7 to PND 12 at a dose of 5 mg/kg, and the animals were sacrificed at PND 13. MD induced increased CORT levels in both genders. MD males also showed an increased number of astrocytes in CA1 and CA3 areas and a significant increase in hippocampal 2‐arachidonoylglycerol. The cannabinoid compounds reversed the endocrine and cellular effects of maternal deprivation. We provide direct evidence for gender‐dependent cellular and biochemical effects of MD on developmental hippocampus, including changes in the endocannabinoid system.

Sex-dependent effects of maternal deprivation and adolescent cannabinoid treatment on adult rat behaviour

Early life experiences such as maternal deprivation (MD) exert long‐lasting changes in adult behaviour and reactivity to stressors. Adolescent exposure to cannabinoids is a predisposing factor in developing certain psychiatric disorders. Therefore, the combination of the two factors could exacerbate the negative consequences of each factor when evaluated at adulthood. The objective of this study was to investigate the long‐term effects of early MD [24 hours at postnatal day (PND) 9] and/or an adolescent chronic treatment with the cannabinoid agonist CP‐55,940 (0.4 mg/kg, PND 28–42) on diverse behavioural and physiological responses of adult male and female Wistar rats. We tested them in the prepulse inhibition (PPI) of the startle response and analysed their exploratory activity (holeboard) and anxiety (elevated plus maze, EPM). In addition, we evaluated their adrenocortical reactivity in response to stress and plasma leptin levels. Maternal behaviour was measured before and after deprivation. MD induced a transient increase of maternal behaviour on reuniting. In adulthood, maternally deprived males showed anxiolytic‐like behaviour (or increased risk‐taking behaviour) in the EPM. Adolescent exposure to the cannabinoid agonist induced an impairment of the PPI in females and increased adrenocortical responsiveness to the PPI test in males. Both, MD and adolescent cannabinoid exposure also induced sex‐dependent changes in plasma leptin levels and body weights. The present results indicate that early MD and adolescent cannabinoid exposure exerted distinct sex‐dependent long‐term behavioural and physiological modifications that could predispose to the development of certain neuropsychiatric disorders, though no synergistic effects were found.

The maternal deprivation animal model revisited.

Early life stress, in the form of MD (24h at pnd 9), interferes with brain developmental trajectories modifying both behavioral and neurobiochemical parameters. MD has been reported to enhance neuroendocrine responses to stress, to affect emotional behavior and to impair cognitive function. More recently, changes in body weight gain, metabolic parameters and immunological responding have also been described. Present data give support to the fact that neuronal degeneration and/or astrocyte proliferation are present in specific brain regions, mainly hippocampus, prefrontal cortex and hypothalamus, which are particularly vulnerable to the effects of neonatal stress. The MD animal model arises as a valuable tool for the investigation of the brain processes occurring at the narrow time window comprised between pnd 9 and 10 that are critical for the establishment of brain circuitries critical for the regulation of behavior, metabolism and energy homeostasis. In the present review we will discuss three possible mechanisms that might be crucial for the effects of MD, namely, the rapid increase in glucocorticoids, the lack of the neonatal leptin surge, and the enhanced endocannabinoid signaling during the specific critical period of MD. A better understanding of the mechanisms underlying the detrimental consequences of MD is a concern for public health and may provide new insights into mental health prevention strategies and into novel therapeutic approaches in neuropsychiatry.

Neuronal and glial alterations in the cerebellar cortex of maternally deprived rats: Gender differences and modulatory effects of two inhibitors of endocannabinoid inactivation

Adult animals submitted to a single prolonged episode of maternal deprivation (MD) [24 h, postnatal day 9–10] show behavioral alterations that resemble specific symptoms of schizophrenia. Accordingly, this experimental procedure has been proposed as an animal model of schizophrenia based on the neurodevelopmental hypothesis. We have recently reported that MD‐induced sex‐dependent alterations in the hippocampus of neonatal rats. In view of recent evidence for important implications of the cerebellum in neurodevelopmental psychiatric diseases, we have now addressed possible degenerative changes in the cerebellar cortex of neonatal Wistar rats of both genders. To evaluate the presence of degenerated nerve cells, we used Fluoro‐Jade C staining and for the study of astrocytes, we employed glial fibrillary acidic protein. Further, we analyzed the modulatory actions of two inhibitors of endocannabinoids inactivation, the fatty acid amide hydrolase inhibitor N‐arachidonoyl‐serotonin, AA‐5‐HT, and the endocannabinoid reuptake inhibitor, OMDM‐2 (daily subcutaneous injections during the postnatal period 7–12). The animals were sacrificed at postnatal Day 13. MD induced significant increases in the number of Fluoro‐Jade C positive cells (indicative of degenerating neurons) and in the number of glial fibrillary acidic protein positive cells, only in males. The two cannabinoid compounds reversed or attenuated these effects. The present results provide new insights regarding the psycopathological implications of the cerebellum, the role of the endocannabinoid system in neural development, and the possible neurodevelopmental basis of gender differences in schizophrenia.

Neurobehavioral and metabolic long-term consequences of neonatal maternal deprivation stress and adolescent olanzapine treatment in male and female rats

Early maternal deprivation (MD), 24h of dam-litter separation on postnatal day (PND) 9, has been proposed as a suitable animal model to investigate some neuropsychiatric disorders with a base in neurodevelopment that also compromises metabolic and endocrine homeostasis. Atypical antipsychotics are frequently prescribed to children and adolescents as first-line treatment for several mental disorders despite the adverse metabolic effects frequently reported. However, persistent long-term effects after adolescent drug therapy have been scarcely investigated. In the present study we aimed to investigate the long-lasting metabolic and behavioral effects of MD in combination with the administration of an atypical antipsychotic, i.e. olanzapine, during adolescence. For that purpose, male and female Wistar rats not exposed (control group, Co) and exposed to the MD protocol were administered with oral olanzapine (Olan, 7.5mg/kg/day) or vehicle (Vh, 1mM acetic acid) in drinking water from PND 28 to PND 49. Body weight gain, glycaemia and plasma triglyceride (TG) levels were evaluated as relevant metabolic parameters. MD significantly diminished body weight gain, while Olan administration only induced a subtle decrease in body weight gain among female animals in the long-term. Olan discontinuation decreased plasma TG levels in adult rats, an effect that was counteracted by neonatal exposure to the MD protocol. Both MD and Olan treatment impaired cognitive function in the novel object recognition test, although no interaction between treatments was observed. Neither MD nor Olan administration affected psychotic-related symptoms evaluated in the prepulse inhibition task, although animals treated with Olan showed an increased reactivity to the first acoustic stimulus. MD diminished the corticosterone stress-induced response among females, and reduced the expression of CB1 receptors in the hippocampus of both male and female rats. Notably, Olan administration tended to counterbalance these two MD-induced effects (i.e. corticosterone response and CB1 receptor expression). Present findings provide evidence for the long-lasting effects of neonatal MD and Olan administration during adolescence, and suggest some sex-dependent interactions between these two protocols. Further research on the interactions between early life stress and antipsychotic drugs is urgently needed, and sex differences should be consistently considered both in animal models and in translation to human studies.

Sex-dependent maternal deprivation effects on brain monoamine content in adolescent rats.

Rats subjected to a single prolonged episode of maternal deprivation (MD) [24h, postnatal days 9-10] show, later in life, behavioural alterations that resemble specific signs of schizophrenia and other neuropsychiatric signs including increased levels of impulsivity and an apparent difficulty to cope with stressful situations. Some of these behavioural modifications are observable in the periadolescent period. However there is no previous information regarding the possible underlying neurochemical correlates at this critical developmental period. In this study we have addressed the effects of MD on the levels of serotonin (5-HT), dopamine (DA) and their respective metabolites in prefrontal cortex, hippocampus, striatum, midbrain and cerebellum of male and female periadolescent Wistar rats. MD rats showed significantly increased levels of 5-HT in all regions studied with the exception of cerebellum. In addition, MD animals showed increased levels of DA in PFC as well as increased levels of DA and a decrease of DOPAC/DA and HVA/DA ratios in striatum. The effect of MD on the monoaminergic systems was in several cases sex-dependent.

Maternal deprivation exacerbates the response to a high fat diet in a sexually dimorphic manner.

Maternal deprivation (MD) during neonatal life has diverse long-term effects, including affectation of metabolism. Indeed, MD for 24 hours during the neonatal period reduces body weight throughout life when the animals are maintained on a normal diet. However, little information is available regarding how this early stress affects the response to increased metabolic challenges during postnatal life. We hypothesized that MD modifies the response to a high fat diet (HFD) and that this response differs between males and females. To address this question, both male and female Wistar rats were maternally deprived for 24 hours starting on the morning of postnatal day (PND) 9. Upon weaning on PND22 half of each group received a control diet (CD) and the other half HFD. MD rats of both sexes had significantly reduced accumulated food intake and weight gain compared to controls when raised on the CD. In contrast, when maintained on a HFD energy intake and weight gain did not differ between control and MD rats of either sex. However, high fat intake induced hyperleptinemia in MD rats as early as PND35, but not until PND85 in control males and control females did not become hyperleptinemic on the HFD even at PND102. High fat intake stimulated hypothalamic inflammatory markers in both male and female rats that had been exposed to MD, but not in controls. Reduced insulin sensitivity was observed only in MD males on the HFD. These results indicate that MD modifies the metabolic response to HFD intake, with this response being different between males and females. Thus, the development of obesity and secondary complications in response to high fat intake depends on numerous factors.

Sex-dependent long-term effects of adolescent exposure to THC and/or MDMA on neuroinflammation and serotoninergic and cannabinoid systems in rats

Many young people consume ecstasy as a recreational drug and often in combination with cannabis. In this study, we aimed to mimic human consumption patterns and investigated, in male and female animals, the long‐term effects of Δ9‐tetrahydrocannabinol (THC) and 3,4‐methylenedioxymethamphetamine (MDMA) on diverse neuroinflammation and neurotoxic markers.

Sex-Dependent Psychoneuroendocrine Effects of THC and MDMA in an Animal Model of Adolescent Drug Consumption

Ecstasy is a drug that is usually consumed by young people at the weekends and frequently, in combination with cannabis. In the present study we have investigated the long-term effects of administering increasing doses of delta-9-tetrahydrocannabinol [THC; 2.5, 5, 10 mg/kg; i.p.] from postnatal day (pnd) 28 to 45, alone and/or in conjunction with 3,4-methylenedioxymethamphetamine [MDMA; two daily doses of 10 mg/kg every 5 days; s.c.] from pnd 30 to 45, in both male and female Wistar rats. When tested one day after the end of the pharmacological treatment (pnd 46), MDMA administration induced a reduction in directed exploration in the holeboard test and an increase in open-arm exploration in an elevated plus maze. In the long-term, cognitive functions in the novel object test were seen to be disrupted by THC administration to female but not male rats. In the prepulse inhibition test, MDMA-treated animals showed a decrease in prepulse inhibition at the most intense prepulse studied (80 dB), whereas in combination with THC it induced a similar decrease at 75 dB. THC decreased hippocampal Arc expression in both sexes, while in the frontal cortex this reduction was only evident in females. MDMA induced a reduction in ERK1/2 immunoreactivity in the frontal cortex of male but not female animals, and THC decreased prepro-orexin mRNA levels in the hypothalamus of males, although this effect was prevented when the animals also received MDMA. The results presented indicate that adolescent exposure to THC and/or MDMA induces long-term, sex-dependent psychophysiological alterations and they reveal functional interactions between the two drugs.