A potential role of hippocampus on impulsivity and alcohol consumption through CB1R.

There are a few studies suggesting that the hippocampus is involved in the regulation of impulsivity, and which attempt to explain drug seeking behavior in addiction. In addition, cannabinoid receptor 1 (CB1R) is highly expressed in the hippocampus (HPP). To further understand the potential role of the hippocampal CB1R in impulsive and drug seeking behaviors, we characterized impulsivity in adolescent and adult male rats, by means of a delay discounting task (DDT) by evaluating preference and seeking motivation for alcohol (10 % v/v) consumption, and analyzing CB1R expression in CA1, CA3 and the dentate gyrus (DG) of the HPP as well as in the medial prefrontal cortex (mPFC). Our results show that adolescent rats display more impulsive choices than adult rats in the DDT. The k value is statistically higher in adolescents, further supporting that they are more impulsive. Besides, adolescent rats have higher forced and voluntary alcohol consumption and display a higher alcohol conditioned place preference (CPP) vs. adult rats. In addition, CB1R expression in CA3 and the DG is higher in adolescent vs. adult rats. Our data further support the role of the hippocampus in impulsivity with the potential involvement of the endocannabinoid system, considering that CB1R in CA3 and DG is higher in adolescents, who display impulsivity and alcohol seeking and consumption.

Total sleep deprivation impairs fear memory retrieval by decreasing the basolateral amygdala activity.

It is well known that sleep deprivation impairs fear memory processes, but little is known about the underlying mechanisms or circuits. The aim of this study was to evaluate the effects of total sleep deprivation (24 h) on contextual fear memory acquisition, consolidation, and retrieval, as well as c-Fos activity in the hippocampus and amygdala. Fear memory recall was associated with an increase in the number of c-Fos-positive cells in the hippocampal CA1 and CA3 regions and the basolateral amygdala (BLA). Total sleep deprivation before to the acquisition and during consolidation of memory impaired retrieval and blocked the associated c-Fos activity in the hippocampus and amygdala. In contrast, total sleep deprivation before memory recall also impaired retrieval, but selectively prevented the increase of c-Fos activity in the amygdala (but not in the hippocampus). Our data indicate that sleep is essential not only for acquisition and consolidation but also for the retrieval of fear memories. They also suggest a differential susceptibility of specific memory-related neural circuits (hippocampus and BLA) to the absence of sleep.

Comparing the effects of endogenous and synthetic cannabinoid receptor agonists on survival of gastric cancer cells.

AIMS: Anti-neoplastic activity induced by cannabinoids has been extensively documented for a number of cancer cell types; however, this topic has been explored in gastric cancer cells only in a limited number of approaches. Thus, the need of integrative and comparative studies still persists. MATERIALS AND METHODS: In this study we tested and compared the effects of three different cannabinoid receptor agonists-anandamide (AEA), (R)-(+)-methanandamide (Meth-AEA) and CP 55,940 (CP)- on gastric cancer cell morphology, viability and death events in order to provide new insights to the use of these agents for therapeutic purposes. KEY FINDINGS: The three agents tested exhibited similar concentration-dependent effects in the induction of changes in cell morphology and cell loss, as well as in the decrease of cell viability and DNA laddering in the human gastric adenocarcinoma cell line (AGS). Differences among the cannabinoids tested were mostly observed in the density of cells found in early and late apoptosis and necrosis, favoring AEA and CP as the more effective inducers of apoptotic mechanisms, and Meth-AEA as a more effective inducer of necrosis through transient and rapid apoptosis. SIGNIFICANCE: Through a comparative approach, our results support and confirm the therapeutic potential that cannabinoid receptor agonists exert in gastric cancer cells and open possibilities to use cannabinoids as part of a new gastric cancer therapy.

On the effects of CP 55-940 and other cannabinoid receptor agonists in C6 and U373 cell lines.

Cannabinoid receptor (CBs) agonists affect the growth of tumor cells via activation of deadly cascades. The spectrum of action of these agents and the precise role of the endocannabinoid system (ECS) on oncogenic processes remain elusive. Herein we compared the effects of synthetic (CP 55-940 and WIN 55,212-2) and endogenous (anandamide or AEA) CBs agonists (10-20 µM) on morphological changes, cell viability, and induction of apoptosis in primary astrocytes and in two glioblastoma cell lines (C6 and U373 cells) in order to characterize their possible differential actions on brain tumor cells. None of the CBs agonist tested induced changes in cell viability or morphology in primary astrocytes. In contrast, CP 55-940 significantly decreased cell viability in C6 and U373 cells at 5 days of treatment, whereas AEA and WIN 55,212-2 moderately decreased cell viability in both cell lines. Treatment of U373 and C6 for 3 and 5 days with AEA or WIN 55,212-2 produced discrete morphological changes in cell bodies, whereas the exposure to CP 55-940 induced soma degradation. CP 55-940 also induced apoptosis in both C6 and U373 cell lines. Our results support a more effective action of CP 55-940 to produce cell death of both cell lines through apoptotic mechanisms. Comparative aspects between cannabinoids with different profiles are necessary for the design of potential treatments against glial tumors.

Cannabinoid type-1 receptors in the paraventricular nucleus of the hypothalamus inhibit stimulated food intake.

Cannabinoid receptor type 1 (CB1)-dependent signaling in the brain is known to modulate food intake. Recent evidence has actually shown that CB1 can both inhibit and stimulate food intake in fasting/refeeding conditions, depending on the specific neuronal circuits involved. However, the exact brain sites where this bimodal control is exerted and the underlying neurobiological mechanisms are not fully understood yet. Using pharmacological and electrophysiological approaches, we show that local CB1 blockade in the paraventricular nucleus of the hypothalamus (PVN) increases fasting-induced hyperphagia in rats. Furthermore, local CB1 blockade in the PVN also increases the orexigenic effect of the gut hormone ghrelin in animals fed ad libitum. At the electrophysiological level, CB1 blockade in slices containing the PVN potentiates the decrease of the activity of PVN neurons induced by long-term application of ghrelin. Hence, the PVN is (one of) the site(s) where signals associated with the body's energy status determine the direction of the effects of endocannabinoid signaling on food intake.

Performance in working memory and attentional control is associated with the rs2180619 SNP in the CNR1 gene.

Individual differences in cognitive performance are partly dependent, on genetic polymporhisms. One of the single-nucleotide polymorphisms (SNP) of the CNR1 gene, which codes for cannabinoid receptor 1 (CB1R), is the rs2180619, located in a regulatory region of this gene (6q14-q15). The alleles of the rs2180619 are A > G; the G allele has been associated with addiction and high levels of anxiety (when the G allele interacts with the SS genotype of the 5-HTTLPR gene). However, GG genotype is observed also in healthy subjects. Considering G allele as risk for 'psychopathological conditions', it is possible that GG healthy subjects do not be addicted or anxious, but would have reduced performance, compared to AA subjects, in attentional control and working memory processing. One hundred and sixty-four healthy young Mexican-Mestizo subjects (100 women and 64, men; mean age: 22.86 years, SD=2.72) participated in this study, solving a task where attentional control and working memory were required. GG subjects, compared to AA subjects showed: (1) a general lower performance in the task (P = 0.02); (2) lower performance only when a high load of information was held in working memory (P = 0.02); and (3) a higher vulnerability to distractors (P = 0.03). Our results suggest that, although the performance of GG subjects was at normal levels, a lower efficiency of the endocannabinoid system, probably due to a lowered expression of CB1R, produced a reduction in the performance of these subjects when attentional control and working memory processing is challenged.

Maternal separation and proclivity for ethanol intake: a potential role of the endocannabinoid system in rats.

Maternal separation (MS) during the first postnatal weeks induces alcohol intake and a reduction in the expression of glucocorticoid receptors (GR). Adults' alcohol consumption may depend on changes in the endocannabinoid system (eCBs). Our goal was to evaluate the status of the eCBs before the exposition to alcohol to support the notion that eCBs' alterations prompt rats to drink alcohol. To reach this goal we subjected rats to MS for the first 2 postnatal weeks. Then, we allowed rats to grow with no further manipulation until they reached adulthood. Thereafter, rats were exposed to an alcohol solution (10% of alcohol in water) as the only source of drinking liquid (forced alcohol ingestion). At the end of this period, tap water was added as an option for drinking liquid (voluntary alcohol ingestion) for another 10 days. Different groups of rats (non-MS, and MS) were sacrificed when adult but with no exposition to alcohol whatsoever, to dissect frontal cortex (FCx), ventral striatum (VS) and hippocampus (HIP) to analyze the following: The expression of cannabinoid receptor 1 (CB1R), CB2R, GR and methylated CpG-binding protein 2 (MeCP2). Levels of GABA and glutamate were quantified in the same brain structures. We found CB1 receptor expression increased in the VS while it was decreased in the FCx in MS subjects. No changes in the CB2R or in the MeCP2 were detected. We found GABA levels increased in FCx and HIP but decreased in VS in MS. Likewise, glutamate levels increased in the FCx but decreased in the HIP in MS subjects. These findings suggest that MS induces changes in the CB1R expression, which might contribute to induce a proclivity to ingest alcohol and, potentially, other drugs.

Oleoylethanolamide affects food intake and sleep-waking cycle through a hypothalamic modulation.

Oleoylethanolamide (OEA) is an endogenous molecule related to endocannabinoids (eCBs) that induces satiety. It binds to the peroxisome-proliferator-activated receptor alpha (PPAR alpha). PPAR alpha is involved in feeding regulation and it has been proposed to play a role in sleep modulation. The objective of the present work is to show if this molecule modifies the sleep-waking cycle through central mechanisms. We have found that the peripheral administration of OEA reduces food intake and increases waking with a concomitant reduction of rapid eye movement sleep. Additionally, this treatment produces deactivation of the lateral hypothalamus, as inferred from the c-Fos expression evaluation. Finally, intra-lateral hypothalamus injection of OEA has mirrored the effects induced by this molecule when it is peripherally administered. In conclusion, we show for the very first time that OEA can modify the sleep-waking cycle and food intake, apparently mediated by the lateral hypothalamus.

The anorexigenic peptide cocaine-and-amphetamine-regulated transcript modulates rem-sleep in rats.

It is known that the sleep-waking cycle is modulated by several molecules that may also regulate food intake, among them several neuropeptides. The cocaine-and-amphetamine-regulated transcript has been studied in relation to food ingestion, but it seems to have several other functions that may include sleep regulation. In this context, we studied the effect of the intracerebroventricular administration of the cocaine-and-amphetamine-regulated transcript (0.15, 0.3, 0.6, 0.9nmol) on the sleep-waking cycle (12-h recordings), as well as its effect on food intake in rats. Additionally, we analyzed the neuronal activity as measured by c-Fos expression induced by the cocaine-and-amphetamine-regulated transcript in neurons of nuclei involved in the regulation of sleep and feeding behavior. Our main finding is that 0.3nmol of the cocaine-and-amphetamine-regulated transcript increases rapid-eye-movement sleep. In addition, our results further support that this neuropeptide triggers satiety; c-Fos expression suggested that the cocaine-and-amphetamine-regulated transcript activates specific hypothalamic nuclei without affecting other brain structures known to be involved in sleep regulation. These data further support the notion that a few neuropeptides are involved in the regulation of both the sleep-waking and the hunger-satiety cycles.

[Sleep genes]. / Genes del sueño.

INTRODUCTION: Sleep is a non-learned adaptive strategy that depends on the expression of several neurotransmitters and other molecules. The expression of some of these molecules depends on a number of different genes. Sleep disorders are associated with an inadequate expression of some molecules, which therefore indicates that these genes that code for these molecules participate in the regulation of normal sleep. AIM: To discuss the evidence on gene regulation over the occurrence of sleep and its architecture, as well as of sleep disorders, which supports the participation of specific genes. DEVELOPMENT: We describe the evidence on sleep in mammals, particularly in humans, in addition to studies with twins that demonstrate the influence of genes on sleep regulation. We also discuss several sleep disorders, which in this study only serves to emphasise how certain specific genes, under normal conditions, participate in the expression of sleep. Furthermore, evidence is also provided for other molecules, such as endocannibinoids, involved in sleep regulation. Lastly, we report on studies conducted with different strains of mice that show differences in the amount of sleep they express, possibly as an epiphenomenon of their different genetic loads. CONCLUSIONS: A number of different genes have been described as those responsible for making us sleep, although sleeping also depends on our interaction with the environment. This interaction is what makes us express sleep at times that are best suited to favouring our survival.

Genes del sueño / Sleep Genes

Resumen. Introducción. El sueño es una estrategia adaptativa no aprendida que depende de la expresión de diversos neurotransmisores y otras moléculas. La expresión de varias de estas moléculas depende de diversos genes. Alteraciones del dormir se asocian con una inadecuada expresión de algunas moléculas, que indican entonces que estos genes que codifican estas moléculas participan en la regulación del sueño normal. Objetivo. Discutir la evidencia de la regulación de los genes sobre la ocurrencia del sueño y su arquitectura, así como de alteraciones del sueño, que sustenta la participación de genes específicos. Desarrollo. Se describe la evidencia sobre el sueño en mamíferos, particularmente en humanos, así como estudios con gemelos que evidencian la influencia genética en la regulación del sueño. Posteriormente, se discuten algunas alteraciones del sueño, que en esta revisión sólo sirven para enfatizar cómo ciertos genes específicos, en condiciones normales, participan en la expresión del sueño. Además, se da evidencia sobre otras moléculas, como los endocannabinoides, que participan en la regulación del sueño. Por último, se describen los estudios con diferentes cepas de ratones que manifiestan diferencias en la cantidad de sueño que expresan, posiblemente como epifenómeno de sus diferentes cargas genéticas. Conclusiones. Se han descrito diversos genes que nos hacen dormir, aunque dormir también depende de la interacción con el medio ambiente. Esta interacción es la que nos hace expresar el sueño en los momentos más convenientes para sobrevivir (AU)

Summary. Introduction. Sleep is a non-learned adaptive strategy that depends on the expression of several neurotransmitters and other molecules. The expression of some of these molecules depends on a number of different genes. Sleep disorders are associated with an inadequate expression of some molecules, which therefore indicates that these genes that code for these molecules participate in the regulation of normal sleep. Aim. To discuss the evidence on gene regulation over the occurrence of sleep and its architecture, as well as of sleep disorders, which supports the participation of specific genes. Development. We describe the evidence on sleep in mammals, particularly in humans, in addition to studies with twins that demonstrate the influence of genes on sleep regulation. We also discuss several sleep disorders, which in this study only serves to emphasise how certain specific genes, under normal conditions, participate in the expression of sleep. Furthermore, evidence is also provided for other molecules, such as endocannibinoids, involved in sleep regulation. Lastly, we report on studies conducted with different strains of mice that show differences in the amount of sleep they express, possibly as an epiphenomenon of their different genetic loads. Conclusions. A number of different genes have been described as those responsible for making us sleep, although sleeping also depends on our interaction with the environment. This interaction is what makes us express sleep at times that are best suited to favouring our survival (AU)

Pharmacological enhancement of the endocannabinoid system in the nucleus accumbens shell stimulates food intake and increases c-Fos expression in the hypothalamus.

BACKGROUND AND PURPOSE: Evidence indicates that the endocannabinoid, 2-arachidonoylglycerol (2-AG), increases food intake when injected into the nucleus accumbens shell (NAcS), thereby potentially activating hypothalamic nuclei involved in food intake regulation. We aimed to evaluate potential orexigenic effects of the endocannabinoid anandamide and of AA5HT, a fatty acid amide hydrolase (FAAH) inhibitor, and OMDM-1, an inhibitor of anandamide uptake, injected in the NAcS, as well as the effect of these treatments on activation of hypothalamic nuclei. EXPERIMENTAL APPROACH: Drugs were given into the NAcS of rats and food intake quantified during the next 4 h. In other groups, after the same treatments the brains were processed for c-Fos immunohistochemistry with focus on hypothalamic nuclei. Additional groups were used to quantify endocannabinoid levels in the nucleus accumbens and the hypothalamus after AA5HT and OMDM-1 intra-NAcS injections. KEY RESULTS: Our results indicate that the above treatments stimulate food intake during 4 h post-injection. They also increase c-Fos immunoreactivity in hypothalamic nuclei. The CB(1) antagonist, AM251, blocked these effects. Finally, we found elevated levels of 2-AG, but not anandamide, after intra-NAcS injections of AA5HT. CONCLUSIONS AND IMPLICATIONS: These data support the involvement of the endocannabinoid system in feeding behavior at the level of the NAcS and hypothalamus. In addition, this is the first experimental demonstration that the pharmacological inhibition of endocannabinoid inactivation in the NAcS stimulates food intake, suggesting that the endocannabinoid degrading proteins can be a target for treating eating disorders.

De la restauración neuronal a la reorganización de los circuitos neuronales: una aproximación a las funciones del sueño / From neuronal recovery to the reorganisation of neuronal circuits: a review of the functions of sleep

Objetivo. Analizar datos y conceptos que se han generadoen torno a una de las funciones propuestas para el sueño: la restauraciónneuronal. Desarrollo. El sueño es un estado de concienciadiferente de la vigilia. Los mamíferos invierten una buena partede su vida en dormir; por ejemplo, los humanos dormimos una terceraparte de nuestra vida, pero ¿para qué invertir tanto tiempo enun estado donde perdemos contacto con el entorno?, ¿qué pasaríasi no durmiéramos? La privación de sueño total altera procesoscognitivos, como la memoria o la atención; si esta privación seprolonga, el sujeto se deteriora y muere. Se ha propuesto que elsueño sirve para restaurar a los organismos del desgaste ocurridodurante la vigilia y, dado que los primeros efectos de la ausenciade sueño se observan en procesos que dependen directamente delcerebro, se ha sugerido que la restauración neuronal es su principalobjetivo. En este trabajo se analizan algunos estudios sobre losefectos de la privación de sueño total en humanos y ratas, así comola relación entre el sueño y el sistema de las neurotrofinas, el cualpromueve la supervivencia y la restauración neuronal. Finalmente,se discuten teorías recientes sobre la función del sueño. Conclusiones.La restauración de las neuronas no es el fin último del sueño,sino mantener y reorganizar los circuitos neuronales, incluyendo laneoformación de sinapsis, que permiten modificar redes neuronalesexistentes, por efecto de la experiencia, y todo esto para el adecuadofuncionamiento del cerebro y su adaptación al ambiente

Aim. To analyse the data and concepts that have been produced in relation to one of the functions that have beensuggested for sleep, namely, neuronal recovery. Development. Sleep is a state of consciousness that is different to that ofarousal. Mammals devote an important part of their lives to sleeping; for example, as humans, we sleep for a third of our lives,but why do we spend so much time in a state where we lose contact with our surroundings? What would happen if we didn’tsleep? Total sleep deprivation alters cognitive processes such as memory or attention, and if this deprivation is prolonged, theindividual deteriorates and dies. It has been suggested that sleep provides the organism with time to recover from the wear andtear that occurs during the waking state and, given that the first effects of the absence of sleep are seen to affect processes thatare directly dependent on the brain, it has been claimed that its main purpose is to allow neuronal recovery. In this work weanalyse some of the studies on the effects of total sleep deprivation in humans and rats, as well as the relationship betweensleep and the neurotrophin system, which promotes neuronal survival and recovery. Finally, the latest theories about thefunction of sleep are discussed. Conclusions. Neuron recovery is not the ultimate purpose of sleep; rather it is to allow formaintenance and reorganisation of neuronal circuits, including new synapse formation, which enables existing neuronalnetworks to be modified by the effect of experience, and all this makes it possible for the brain to work properly and to adaptitself to the environment

[From neuronal recovery to the reorganisation of neuronal circuits: a review of the functions of sleep]. / De la restauración neuronal a la reorganización de los circuitos neuronales: una aproximación a las funciones del sueño.

AIM: To analyse the data and concepts that have been produced in relation to one of the functions that have been suggested for sleep, namely, neuronal recovery. DEVELOPMENT: Sleep is a state of consciousness that is different to that of arousal. Mammals devote an important part of their lives to sleeping; for example, as humans, we sleep for a third of our lives, but why do we spend so much time in a state where we lose contact with our surroundings? What would happen if we didn't sleep? Total sleep deprivation alters cognitive processes such as memory or attention, and if this deprivation is prolonged, the individual deteriorates and dies. It has been suggested that sleep provides the organism with time to recover from the wear and tear that occurs during the waking state and, given that the first effects of the absence of sleep are seen to affect processes that are directly dependent on the brain, it has been claimed that its main purpose is to allow neuronal recovery. In this work we analyse some of the studies on the effects of total sleep deprivation in humans and rats, as well as the relationship between sleep and the neurotrophin system, which promotes neuronal survival and recovery. Finally, the latest theories about the function of sleep are discussed. CONCLUSIONS: Neuron recovery is not the ultimate purpose of sleep; rather it is to allow for maintenance and reorganisation of neuronal circuits, including new synapse formation, which enables existing neuronal networks to be modified by the effect of experience, and all this makes it possible for the brain to work properly and to adapt itself to the environment.

[The development of attention, memory and the inhibitory processes: the chronological relation with the maturation of brain structure and functioning]. / Desarrollo de la atención, la memoria y los procesos inhibitorios: relación temporal con la maduración de la estructura y función cerebral.

Development during childhood and adolescence is characterized by greater efficiency in performing cognitive tasks. The correlations between cognitive and brain development are not altogether clear and have not been studied in depth. The aim of this study is to survey the research carried out into the development of cognitive functioning in children, adolescents and adults, and its chronological relation with brain development. Anatomofunctional and cognitive-behavioural studies are presented. Anatomical studies have shown that the white matter increases linearly throughout childhood and adolescence, whereas cortical and subcortical grey matter increases in the pre-adolescent period and later diminishes in the post adolescent stage. It has been claimed that these changes are regional and that the prefrontal cortex (PFC) is one of the last areas to mature. Functional research has studied cognitive processes attributed to the functioning of the PFC, such as attention, working memory and the inhibition of irrelevant responses. The findings from these studies have shown a behavioural and physiological development of these three processes during childhood and adolescence. Behavioural results have evidenced greater efficiency in capacities such as discriminating between relevant and irrelevant information, storing and handling information in the memory and the inhibition of unsuitable responses during the performance of a task. The physiological results have presented changes in the magnitude, spread and integration of the regions activated during task performance. Cognitive and behavioural maturation is consecutive to structural and physiological maturing and this is produced in a chronologically and qualitatively different way in the distinct regions of the brain.

Desarrollo de la atención, la memoria y los procesos inhibitorios: relación temporal con la maduración de la estructura y función cerebral / The development of attention, memory and the inhibitory processes: the chronological relation with the maturation of brain structure and functioning

El desarrollo durante la niñez y la adolescencia se caracteriza por una mayor eficiencia en la realización de tareas cognitivas. Las correlaciones entre el desarrollo cognitivo y el cerebral no son claras y no se han estudiado profundamente. El objetivo de este trabajo es revisar las investigaciones sobre el desarrollo del funcionamiento cognitivo en niños, adolescentes y adultos, así como su relación temporal con el desarrollo cerebral. Se presentan estudios anatomofuncionales y cognitivocomportamentales. Los estudios anatómicos han mostrado que la sustancia blanca aumenta linealmente durante la niñez y la adolescencia, mientras que la sustancia gris cortical y subcortical tienen un incremento en la etapa preadolescente, seguido por una disminución en la etapa postadolescente. Se ha comunicado que estos cambios son regionales y que la corteza prefrontal (CPF) es una de las últimas zonas en madurar. Las investigaciones funcionales han estudiado procesos cognitivos atribuidos al funcionamiento de la CPF, tales como la atención, la memoria de trabajo y la inhibición de respuestas irrelevantes. Los resultados de estos estudios han mostrado un desarrollo conductual y fisiológico de estos tres procesos durante la niñez y la adolescencia. Los resultados conductuales han objetivado una mayor eficiencia de capacidades como la discriminación entre información relevante e irrelevante, el almacenamiento y manipulación de información en la memoria y la inhibición de respuestas inadecuadas durante la ejecución de una tarea. Los resultados fisiológicos han presentado cambios en la magnitud, dispersión e integración de las regiones activadas durante la ejecución de tareas. La maduración cognitiva y conductual es consecutiva a la estructural y fisiológica y ésta se produce de manera diferente, tanto cronológica como cualitativamente, en las distintas regiones cerebrales (AU)

Development during childhood and adolescence is characterized by greater efficiency in performing cognitive tasks. The correlations between cognitive and brain development are not altogether clear and have not been studied in depth. The aim of this study is to survey the research carried out into the development of cognitive functioning in children, adolescents and adults, and its chronological relation with brain development. Anatomofunctional and cognitive-behavioural studies are presented. Anatomical studies have shown that the white matter increases linearly throughout childhood and adolescence, whereas cortical and subcortical grey matter increases in the pre-adolescent period and later diminishes in the post-adolescent stage. It has been claimed that these changes are regional and that the prefrontal cortex (PFC) is one of the last areas to mature. Functional research has studied cognitive processes attributed to the functioning of the PFC, such as attention, working memory and the inhibition of irrelevant responses. The findings from these studies have shown a behavioural and physiological development of these three processes during childhood and adolescence. Behavioural results have evidenced greater efficiency in capacities such as discriminating between relevant and irrelevant information, storing and handling information in the memory and the inhibition of unsuitable responses during the performance of a task. The physiological results have presented changes in the magnitude, spread and integration of the regions activated during task performance. Cognitive and behavioural maturation is consecutive to structural and physiological maturing and this is produced in a chronologically and qualitatively different way in the distinct regions of the brain (AU)

Potential role of the cannabinoid receptor CB1 in rapid eye movement sleep rebound.

Sleep is an unavoidable activity of the brain. The delay of the time to sleep (sleep deprivation), induces an increase of slow-wave sleep and rapid-eye-movement (REM) sleep (rebound) once the subject is allowed to sleep. This drive to sleep has been hypothesized to be dependent on the accumulation of sleep-inducing molecules and on the high expression of these molecule receptors. In this study we selectively deprived rats of REM sleep for 24 h by using the flowerpot technique. One group deprived of REM sleep was treated with SR141716A, a cannabinoid receptor 1 (CB1) receptor antagonist and then allowed to sleep for the next 4 h. Two other groups were killed, one immediately after the REM sleep deprivation period and the other after 2 h of REM sleep rebound (REM sleep deprivation plus 2 h of rebound). In both groups we determined the expression of the CB1 receptor and its mRNA. Results indicated that SR141716A prevents REM sleep rebound and REM sleep deprivation does not modify the expression of the CB1 protein or mRNA. However, REM sleep deprivation plus 2 h of sleep rebound increased the CB1 receptor protein and, slightly but significantly, decreased mRNA expression. These results suggest that endocannabinoids may be participating in the expression of REM sleep rebound.

Oleamide modulates memory in rats.

Oleamide is a recently described lipid, obtained from the cerebrospinal fluid of sleep-deprived cats. It has been observed that oleamide possesses several biological effects, such as sleep induction, and immunological suppression as well as serotonin and gamma-aminobutyric acid receptors activation. In addition, oleamide also binds to the cannabinoid receptors. In this study, we have observed that oleamide facilitates memory extinction in a passive avoidance paradigm, reduces core temperature and pain perception, but does not affect significantly locomotion. These results suggest that oleamide modulates memory processes. However, we do not know if oleamide impairs the retrieval of the memory associated to the "not go" behavior, or facilitates the fast re-learning of the "go" behavior. In addition, since these effects are also induced by marijuana and anandamide, it is very likely that oleamide may be affecting the cerebral cannabinoid system to induce its effects.

Inhibition of the ERK pathway prevents HIVgp120-induced REM sleep increase.

Approximately 35% of HIV-infected subjects, both children and adults, exhibit alterations in the sleep-waking cycle. HIV surface glycoprotein gp120 has been postulated to contribute to this abnormality. For example, it has been reported that HIVgp120 modifies sleep in freely-moving rats and that it also activates the ERK pathway in brain slices. The goal of this work was to determine if sleep changes induced by HIVgp120 in normal rats are mediated by the MAPK pathway. Our results show that a single intraventricular administration of HIVgp120 selectively increases REMS and that such an increase can be prevented by U0126, an inhibitor of ERK activating enzyme, MEK. In contrast, SB202190, a MAPK-p38 inhibitor, had no effect on HIVgp120-induced increase in REMS. These results suggest that HIVgp120 increases REMS in the rat by specifically affecting the ERK signal transduction pathway.

Anandamide-induced sleep is blocked by SR141716A, a CB1 receptor antagonist and by U73122, a phospholipase C inhibitor.

Anandamide (ANA) alters sleep by increasing the amount of time spent in slow wave sleep 2 (SWS2) and rapid eye movement sleep (REMS) at the expense of wakefulness (W) in rats. In this report, we describe a similar effect of ANA when injected itracerebroventricularly (i.c.v.) or into the peduriculopontine tegmental nucleus (PPTg) and the lack of an effect when ANA is administered into the medial preoptic area (MPOA). Furthermore, the i.c.v. or PPTg administration of SR141716A, a CB1 antagonist, or U73122, a PLC inhibitor, 15 min prior to ANA, readily prevents the ANA induced changes in sleep. The present results suggest that a cannabinoid system in the PPTg may be involved in sleep regulation and that the cannabinoid effect is mediated by the CB1 receptor coupled to a PLC second messenger system.