Cannabis and the developing brain: insights from behavior

Chronic administration during early adulthood does not alter the hormonally-dependent disruptive effects of delta-9-tetrahydrocannabinol (Δ9-THC) on complex behavior in female rats

This study examined whether chronic Δ(9)-THC during early adulthood would produce the same hormonally-dependent deficits in learning that are produced by chronic Δ(9)-THC during adolescence. To do this, either sham-operated (intact) or ovariectomized (OVX) female rats received daily saline or 5.6 mg/kg of Δ(9)-THC i.p. for 40 days during early adulthood. Following chronic administration, and a drug-free period to train both a learning and performance task, acute dose-effect curves for Δ(9)-THC (0.56-10 mg/kg) were established in each of the four groups (intact/saline, intact/THC, OVX/saline and OVX/THC). The dependent measures of responding under the learning and performance tasks were the overall response rate and the percentage of errors. Although the history of OVX and chronic Δ(9)-THC in early adulthood did not significantly affect non-drug or baseline behavior under the tasks, acute administration of Δ(9)-THC produced both rate-decreasing and error-increasing effects on learning and performance behavior, and these effects were dependent on their hormone condition. More specifically, both intact groups were more sensitive to the rate-decreasing and error-increasing effects of Δ(9)-THC than the OVX groups irrespective of chronic Δ(9)-THC administration, as there was no significant main effect of chronic treatment and no significant interaction between chronic treatment (saline or Δ(9)-THC) and the dose of Δ(9)-THC administered as an adult. Post mortem examination of 10 brain regions also indicated there were significant differences in agonist-stimulated GTPγS binding across brain regions, but no significant effects of chronic treatment and no significant interaction between the chronic treatment and cannabinoid signaling. Thus, acute Δ(9)-THC produced hormonally-dependent effects on learning and performance behavior, but a period of chronic administration during early adulthood did not alter these effects significantly, which is contrary to what we and others have shown for chronic administration during adolescence.

Marijuana: current concepts(†)

Marijuana (cannabis) remains a controversial drug in the twenty-first century. This paper considers current research on use of Cannabis sativa and its constituents such as the cannabinoids. Topics reviewed include prevalence of cannabis (pot) use, other drugs consumed with pot, the endocannabinoid system, use of medicinal marijuana, medical adverse effects of cannabis, and psychiatric adverse effects of cannabis use. Treatment of cannabis withdrawal and dependence is difficult and remains mainly based on psychological therapy; current research on pharmacologic management of problems related to cannabis consumption is also considered. The potential role of specific cannabinoids for medical benefit will be revealed as the twenty-first century matures. However, potential dangerous adverse effects from smoking marijuana are well known and should be clearly taught to a public that is often confused by a media-driven, though false message and promise of benign pot consumption.

The endocannabinoid system in normal and pathological brain ageing

The role of endocannabinoids as inhibitory retrograde transmitters is now widely known and intensively studied. However, endocannabinoids also influence neuronal activity by exerting neuroprotective effects and regulating glial responses. This review centres around this less-studied area, focusing on the cellular and molecular mechanisms underlying the protective effect of the cannabinoid system in brain ageing. The progression of ageing is largely determined by the balance between detrimental, pro-ageing, largely stochastic processes, and the activity of the homeostatic defence system. Experimental evidence suggests that the cannabinoid system is part of the latter system. Cannabinoids as regulators of mitochondrial activity, as anti-oxidants and as modulators of clearance processes protect neurons on the molecular level. On the cellular level, the cannabinoid system regulates the expression of brain-derived neurotrophic factor and neurogenesis. Neuroinflammatory processes contributing to the progression of normal brain ageing and to the pathogenesis of neurodegenerative diseases are suppressed by cannabinoids, suggesting that they may also influence the ageing process on the system level. In good agreement with the hypothesized beneficial role of cannabinoid system activity against brain ageing, it was shown that animals lacking CB1 receptors show early onset of learning deficits associated with age-related histological and molecular changes. In preclinical models of neurodegenerative disorders, cannabinoids show beneficial effects, but the clinical evidence regarding their efficacy as therapeutic tools is either inconclusive or still missing.

The impact of cannabis use on age of onset and clinical characteristics in first-episode psychotic patients. Data from the Psychosis Incident Cohort Outcome Study (PICOS)

Cannabis use is frequent among first-episode psychosis (FEP) patients and has been associated with several clinical features. This study aimed in an FEP sample to determine whether cannabis use is associated with (1) a higher level of positive symptoms, a lower level of depression and a better premorbid adjustment, (2) an earlier age of onset, and a better premorbid IQ. The study was conducted within the framework of the Psychosis Incident Cohort Outcome Study (PICOS), a multisite collaborative research on FEP patients who attended the psychiatric services in Veneto Region, Italy. Standardized instruments were used to collect sociodemographic, clinical, and drug use data. A total of 555 FEP patients met the inclusion criteria, 517 of whom received an ICD-10 diagnosis of psychosis; 397 (55% males; mean age: 32 yrs ± 9.5) were assessed. Out of these, 311 patients agreed to be interviewed on drug and alcohol misuse; 20.3% was positive for drug misuse: cannabis (19.0%), cocaine (3.9%), and hallucinogens (3.9%). Cannabis use was not associated with a higher level of positive symptoms, but correlated with less severe depressive symptoms. No relationship was observed between premorbid adjustment or IQ and cannabis use. FEP patients who used cannabis had an earlier age of onset than abstinent patients, even after adjusting for gender and diagnosis. Our results suggest a possible causal role of cannabis in triggering psychosis in certain vulnerable subjects. Particular attention must be paid to this behaviour, because reducing cannabis use can delay or prevent some cases of psychosis.

Impulsivity, attention, memory, and decision-making among adolescent marijuana users

RATIONALE

Marijuana is a popular drug of abuse among adolescents, and they may be uniquely vulnerable to resulting cognitive and behavioral impairments. Previous studies have found impairments among adolescent marijuana users. However, the majority of this research has examined measures individually rather than multiple domains in a single cohesive analysis. This study used a logistic regression model that combines performance on a range of tasks to identify which measures were most altered among adolescent marijuana users.

OBJECTIVES

The purpose of this research was to determine unique associations between adolescent marijuana use and performances on multiple cognitive and behavioral domains (attention, memory, decision-making, and impulsivity) in 14- to 17-year-olds while simultaneously controlling for performances across the measures to determine which measures most strongly distinguish marijuana users from nonusers.

METHODS

Marijuana-using adolescents (n = 45) and controls (n = 48) were tested. Logistic regression analyses were conducted to test for: (1) differences between marijuana users and nonusers on each measure, (2) associations between marijuana use and each measure after controlling for the other measures, and (3) the degree to which (1) and (2) together elucidated differences among marijuana users and nonusers.

RESULTS

Of all the cognitive and behavioral domains tested, impaired short-term recall memory and consequence sensitivity impulsivity were associated with marijuana use after controlling for performances across all measures.

CONCLUSIONS

This study extends previous findings by identifying cognitive and behavioral impairments most strongly associated with adolescent marijuana users. These specific deficits are potential targets of intervention for this at-risk population.

Street drug use during pregnancy: potential programming effects on preschool wheeze

Street drug use during pregnancy is detrimental to fetal development. Although the prevalence of wheeze is high in offspring of substance-abusing mothers, nothing is known about the role of street drug use during pregnancy in its development. We investigated the impact of maternal street drug use and distress during pregnancy on the development of wheeze and allergy in preschool children. Questionnaire data were accessed from the Community Perinatal Care trial of 791 mother–child pairs in Calgary, Alberta. Using logistic regression, the association between maternal substance use and distress during pregnancy, and wheeze and allergy at age 3 years was determined in boys and girls. After adjusting for alcohol use during pregnancy, pre- and postnatal tobacco use, preterm birth, duration of exclusive breastfeeding, daycare attendance and maternal socioeconomic status, maternal street drug use during pregnancy [odds ratio (OR): 5.02, 95% confidence interval (CI): 1.30–19.4] and severe maternal distress during pregnancy (OR: 5.79, 95% CI: 1.25–26.8) were associated with wheeze in girls. In boys, an independent association was found between severe distress during pregnancy (OR: 3.85, 95% CI: 1.11–13.3) and allergies, but there was no association with maternal street drug use. In conclusion, we found an association between maternal street drug use and wheeze in preschool girls that could not be accounted for by maternal distress, smoking or alcohol use during pregnancy. Prenatal programming effects of street drugs may explain this association.

Acetaminophen differentially enhances social behavior and cortical cannabinoid levels in inbred mice

Supratherapeutic doses of the analgesic acetaminophen (paracetomol) are reported to promote social behavior in Swiss mice. However, we hypothesized that it might not promote sociability in other strains due to cannabinoid CB(1) receptor-mediated inhibition of serotonin (5-HT) transmission in the frontal cortex. We examined the effects of acetaminophen on social and repetitive behaviors in comparison to a cannabinoid agonist, WIN 55,212-2, in two strains of socially-deficient mice, BTBR and 129S1/SvImJ (129S). Acetaminophen (100mg/kg) enhanced social interactions in BTBR, and social novelty preference and marble burying in 129S at serum levels of ≥70 ng/ml. Following acetaminophen injection or sociability testing, anandamide (AEA) increased in BTBR frontal cortex, while behavior testing increased 2-arachidonyl glycerol (2-AG) levels in 129S frontal cortex. In contrast, WIN 55,212-2 (0.1mg/kg) did not enhance sociability. Further, we expected CB(1)-deficient (+/-) mice to be less social than wild-type, but instead found similar sociability. Given strain differences in endocannabinoid response to acetaminophen, we compared cortical CB(1) and 5-HT(1A) receptor density and function relative to sociable C57BL/6 mice. CB(1) receptor saturation binding (Bmax=958±117 fmol/mg protein), and affinity for [(3)H] CP55,940 (K(D)=3±0.8 nM) was similar in frontal cortex among strains. CP55,940-stimulated [(35)S] GTPγS binding in cingulate cortex was 136±12, 156±22, and 75±9% above basal in BTBR, 129S and C57BL/6 mice. The acetaminophen metabolite para-aminophenol (1 μM) failed to stimulate [(35)S] GTPγS binding. Hence, it appears that other indirect actions of acetaminophen, including 5-HT receptor agonism, may underlie its sociability promoting properties outweighing any CB(1) mediated suppression by locally-elevated endocannabinoids in these mice.

Exploration of the comorbidity of cannabis use disorders and mental health disorders among inpatients presenting to all hospitals in New South Wales, Australia

BACKGROUND

Cannabis is one of the most commonly used illegal psychoactive substances and its use often coexists with mental health disorders.

OBJECTIVES

This study explores the relationships between cannabis use disorders and some common mental health disorders.

METHODS

Admissions to all New South Wales (NSW) hospitals were analyzed. The data were extracted from the NSW Department of Health Inpatient Statistics Data Collection for the period 1 July 2006 to 30 June 2007. Readmissions within 28 days were excluded. Data extraction and analyses were performed by using the SAS program. Chi-square tests and odds ratio were used to examine the association between cannabis use disorder and mental health disorders.

RESULTS

Of the 1.8 million admissions, associations between cannabis use disorders and mental health disorders were strong (odds ratio = 7.8-10.7, p < .001). Inpatients (53.8%) who used cannabis had at least one identifiable mental disorder. Higher comorbidity rates were observed for females (39.6%) and for those aged between 30 and 49 years. Cannabis use disorder comorbid with the most common mental disorders were: anxiety disorder (3.4%), bipolar affective disorder (5.7%), major depressive disorder (10.9%), personality disorder (9.2%), schizophrenia (15.0%), and severe stress disorder (8.7%). Cannabis use disorder has strong associations with these mental health disorders (odds ratio 4.8-34.8). The average length of stay (ALOS) for cannabis use disorders was 9.0 days and the ALOS for the most common mental health disorders was 11.0 days.

CONCLUSIONS AND IMPLICATIONS

This study provides detailed information about the association between cannabis use disorders and mental health disorders and extends our understanding of comorbidity presentations in inpatient admissions.

The endocannabinoid transport inhibitor AM404 differentially modulates recognition memory in rats depending on environmental aversiveness

Cannabinoid compounds may influence both emotional and cognitive processes depending on the level of environmental aversiveness at the time of drug administration. However, the mechanisms responsible for these responses remain to be elucidated. The present experiments investigated the effects induced by the endocannabinoid transport inhibitor AM404 (0.5-5 mg/kg, i.p.) on both emotional and cognitive performances of rats tested in a Spatial Open Field task and subjected to different experimental settings, named High Arousal (HA) and Low Arousal (LA) conditions. The two different experimental conditions influenced emotional reactivity independently of drug administration. Indeed, vehicle-treated rats exposed to the LA condition spent more time in the center of the arena than vehicle-treated rats exposed to the HA context. Conversely, the different arousal conditions did not affect the cognitive performances of vehicle-treated animals such as the capability to discriminate a spatial displacement of the objects or an object substitution. AM404 administration did not alter locomotor activity or emotional behavior of animals exposed to both environmental conditions. Interestingly, AM404 administration influenced the cognitive parameters depending on the level of emotional arousal: it impaired the capability of rats exposed to the HA condition to recognize a novel object while it did not induce any impairing effect in rats exposed to the LA condition. These findings suggest that drugs enhancing endocannabinoid signaling induce different effects on recognition memory performance depending on the level of emotional arousal induced by the environmental conditions.

Altering endocannabinoid neurotransmission at critical developmental ages: impact on rodent emotionality and cognitive performance

The endocannabinoid system shows functional activity from early stages of brain development: it plays an important role in fundamental developmental processes such as cell proliferation, migration, and differentiation, thus shaping brain organization during pre- and postnatal life. Cannabis sativa preparations are among the illicit drugs most commonly used by young people, including pregnant women. The developing brain can be therefore exposed to cannabis preparations during two critical periods: first, in offspring of cannabis-using mothers through perinatal and/or prenatal exposure; second, in adolescent cannabis users during neural maturation. In the last decade, it has become clear that the endocannabinoid system critically modulates memory processing and emotional responses. Therefore, it is well possible that developmental exposure to cannabinoid compounds induces enduring changes in behaviors and neural processes belonging to the cognitive and emotional domains. We address this issue by focusing on rodent studies, in order to provide a framework for understanding the impact of cannabinoid exposure on the developing brain.

Adolescent exposure to nicotine and/or the cannabinoid agonist CP 55,940 induces gender-dependent long-lasting memory impairments and changes in brain nicotinic and CB(1) cannabinoid receptors

We have analysed the long-term effects of adolescent (postnatal day 28-43) exposure of male and female rats to nicotine (NIC, 1.4 mg/kg/day) and/or the cannabinoid agonist CP 55,940 (CP, 0.4 mg/kg/day) on the following parameters measured in the adulthood: (1) the memory ability evaluated in the object location task (OL) and in the novel object test (NOT); (2) the anxiety-like behaviour in the elevated plus maze; and (3) nicotinic and CB(1) cannabinoid receptors in cingulated cortex and hippocampus. In the OL, all pharmacological treatments induced significant decreases in the DI of females, whereas no significant effects were found among males. In the NOT, NIC-treated females showed a significantly reduced DI, whereas the effect of the cannabinoid agonist (a decrease in the DI) was only significant in males. The anxiety-related behaviour was not changed by any drug. Both, nicotine and cannabinoid treatments induced a long-lasting increase in CB(1) receptor activity (CP-stimulated GTPγS binding) in male rats, and the nicotine treatment also induced a decrease in nicotinic receptor density in the prefrontal cortex of females. The results show gender-dependent harmful effects of both drugs and long-lasting changes in CB(1) and nicotinic receptors.

Prenatal tetrahydrocannabinol (THC) alters cognitive function and amphetamine response from weaning to adulthood in the rat

Research suggests that not only is marijuana use prevalent among women of reproductive age, but a significant number of women continue to use marijuana and its derivatives throughout pregnancy. Many studies have shown, in both humans and animals, that marijuana exposure during adolescence and adulthood is detrimental to normal cognition and memory. In this study, we examined the effects of daily intravenous injections of 0.15 mg/kg Δ(9)-tetrahydrocannabinol (THC), given to pregnant dams throughout gestation, on cognitive function in the offspring. Offspring were exposed to three tests: a passive avoidance test at postnatal day (PND) 22, an active place avoidance test at PND 45, and an attention task at PND 60, which assessed learning and long-term memory, spatial working memory and prediction, and attention, respectively. Other offspring were also given a 1mg/kg amphetamine challenge at PND 60. Passive avoidance testing showed that prenatal THC had no effect on acquisition but interfered with consolidation during retention testing. The active place avoidance task showed no treatment-related effects on acquisition but a significant treatment effect was observed in reversal performance in males. The attention task showed that a smaller percentage of THC-exposed rats completed the test, although the failure rate of both groups was quite high. Finally, THC exposed animals, both male and female, showed a dampened locomotor response to amphetamine, but females were more active than males overall. These results suggest that prenatal THC exposure has effects on certain aspects of cognitive function in rats from weaning to adulthood. These effects suggest that prenatal marijuana exposure could also alter cognitive function in humans and therefore have an impact on school performance and dampen responses to psychostimulants as well.

Lasting impacts of prenatal cannabis exposure and the role of endogenous cannabinoids in the developing brain

Cannabis is the most commonly used illicit substance among pregnant women. Human epidemiological and animal studies have found that prenatal cannabis exposure influences brain development and can have long-lasting impacts on cognitive functions. Exploration of the therapeutic potential of cannabis-based medicines and synthetic cannabinoid compounds has given us much insight into the physiological roles of endogenous ligands (endocannabinoids) and their receptors. In this article, we examine human longitudinal cohort studies that document the long-term influence of prenatal exposure to cannabis, followed by an overview of the molecular composition of the endocannabinoid system and the temporal and spatial changes in their expression during brain development. How endocannabinoid signaling modulates fundamental developmental processes such as cell proliferation, neurogenesis, migration and axonal pathfinding are also summarized.

Failure to sustain prepulse inhibition in adolescent marijuana users

BACKGROUND

Marijuana use is typically initiated during adolescence, which is a critical period for neural development. Studies have reported reductions in prepulse inhibition (PPI) among adults who use marijuana chronically, although no human studies have been conducted during the critical adolescent period.

METHODS

This study tested PPI of acoustic startle among adolescents who were either frequent marijuana users or naïve to the drug (Controls). Adolescents were tested using two intensities of prepulses (70 and 85 dB) combined with a 105 dB startle stimulus, delivered across two testing blocks.

RESULTS

There was a significant interaction of group by block for PPI; marijuana users experienced a greater decline in the PPI across the testing session than Controls. The change in PPI of response magnitude for users was predicted by change in urine THC/creatinine after at least 18 h of abstinence, the number of joints used during the previous week before testing, as well as self-reported DSM-IV symptoms of marijuana tolerance, and time spent using marijuana rather than participating in other activities.

CONCLUSIONS

These outcomes suggest that adolescents who are frequent marijuana users have problems maintaining prepulse inhibition, possibly due to lower quality of information processing or sustained attention, both of may contribute to continued marijuana use as well as attrition from marijuana treatment.

Cannabis use at a young age is associated with psychotic experiences

BACKGROUND

Cannabis use is associated with psychosis and a range of subclinical psychiatric symptoms. The strength of this association depends on dosage and age at first use. The current study investigates whether level of cannabis exposure and starting age are associated with specific profiles of subclinical symptoms.

METHOD

We collected cross-sectional data from a young adult population sample by administering an online version of the Community Assessment of Psychic Experiences (CAPE). Cannabis exposure was quantified as the amount of Euros spent on cannabis per week and the age of initial cannabis use. The primary outcome measure was the odds ratio (OR) to belong to the highest 10% of scores on the total CAPE and the positive-, negative- and depressive symptom dimensions.

RESULTS

In 17 698 adolescents (mean age 21.6, s.d.=4.2 years), cannabis use at age 12 years or younger was strongly associated with a top 10% score on psychotic experiences [OR 3.1, 95% confidence interval (CI) 2.1-4.3] and to a lesser degree with negative symptoms (OR 1.7, 95% CI 1.1-2.5). The OR of heavy users (>€25/week) for negative symptoms was 3.4 (95% CI 2.9-4.1), for psychotic experiences 3.0 (95% CI 2.4-3.6), and for depressive symptoms 2.8 (95% CI 2.3-3.3).

CONCLUSIONS

Early start of cannabis use is strongly associated with subclinical psychotic symptoms and to a lesser degree with negative symptoms, while smoking high amounts of cannabis is associated with increased levels of all three symptom dimensions: psychotic, negative and depressive. These results support the hypothesis that the impact of cannabis use is age specific.

Fünf Minuten täglich: Kompass – eine stationäre Kurzintervention für junge Cannabis-/Partydrogen- patienten nach dem „Bonner Modell – Junge Sucht“

Fragestellung: Zur stationären Behandlung von Cannabis-/Partydrogenkonsumenten wurde eine Kurzinterventionsmethode „Kompass“ mit einem Zeitaufwand von täglich fünf Minuten entwickelt und auf ihre Wirksamkeit insbesondere hinsichtlich der depressiven Symptomatik und den besonderen Bedürfnissen der Patientengruppe überprüft. Methodik: 104 Patienten im Alter von 23, davon 66 Cannabis- und 21 Partydrogenkonsumenten , die sich in der LVR-Klinik Bonn stationär in Behandlung befanden, wurden anhand standardisierter Fragebögen (BDI, Hautzinger, Bailer, Worrall & Keller, 1995 ; IIP-C, Horowitz, Strauß & Kordy, 2000 ; STAI, Laux, Glanzmann, Schaffner & Spielberger, 1981 ; SCL-90-R, Franke, 2005 ) und Interviews (EuropASI, Gsellhofer & Blanken, 1999 ) in einem quasi-experimentellem Design untersucht. Der Therapieerfolg (Symptomreduktion) wurde über die korrigierte Effektstärke erfasst. Ergebnisse: Die Kurzinterventionsmethode „Kompass“ ist ein in der stationären Behandlung wirksames Zusatztreatment. Im Vergleich zu einer „Treatment-as-usual“-Gruppe wurden mit dkorr = 0.70 für interpersonale Probleme, dkorr = 0.60 für Trait-Angst, dkorr = 0.56 für Depressivität und dkorr = 0.60 für psychische Belastung mittlere Effektstärken gefunden. Schlussfolgerung: Der „Kompass“ kann effektiv und effizient als Zusatzbehandlung in die stationäre Therapie für Cannabis-/Partydrogenkonsumentent integriert werden.

Cannabis use in young people: the risk for schizophrenia

Cannabis is one of the most commonly used illicit drugs, and despite the widely held belief that it is a safe drug, its long-term use has potentially harmful consequences. To date, the research on the impact of its use has largely been epidemiological in nature and has consistently found that cannabis use is associated with schizophrenia outcomes later in life, even after controlling for several confounding factors. While the majority of users can continue their use without adverse effects, it is clear from studies of psychosis that some individuals are more vulnerable to its effects than others. In addiction, evidence from both epidemiological and animal studies indicates that cannabis use during adolescence carries particular risk. Further studies are warranted given the increase in the concentration of the main active ingredient (Δ(9)-tetrahydrocannabinol) in street preparations of cannabis and a decreasing age of first-time exposure to cannabis.

Cannabinoid effects on CB1 receptor density in the adolescent brain: an autoradiographic study using the synthetic cannabinoid HU210

The short- and long-term behavioral effects of cannabinoids differ in adolescent and adult rodents. Few studies though have examined the underlying neurochemical changes that occur in the brain following adolescent cannabinoid exposure. In this study, we examined the effect of treatment with the synthetic cannabinoid, HU210, on CB1 receptor density in the brain and on body weight in adolescent male rats. Rats were treated daily with 25, 50, or 100 μg/kg HU210 for 4 or 14 days, or received a single dose of 100 μg/kg HU210 and sacrificed 24 h later. Receptor density was investigated using in vitro autoradiography with the CB1 receptor ligand [(3)H] CP55,940. In contrast to adult animals treated under the same paradigm in a previous study, adolescents continued on average, to gain weight over the course of the study. Weight gain was slowest in the 100 μg/kg group and improved dose dependently with controls gaining the most weight. Following the acute dose of HU210, a trend for a reduction in [(3)H] CP55,940 binding and a significant effect of treatment was observed. Statistically significant, dose-dependent, region-specific decreases in binding were observed in all brain regions examined following 4 and 14 days treatment. The pattern of CB1 receptor downregulation was similar to that observed in adults treated with cannabinoids in previous studies; however, its magnitude was smaller in adolescents. This reduced compensatory response may contribute to some acute behavioral effects, the pharmacological cross-tolerance and the long-lasting, adverse psychological consequences of cannabinoid exposure during adolescence.

Long-term behavioral and pharmacodynamic effects of delta-9-tetrahydrocannabinol in female rats depend on ovarian hormone status

Abuse of Δ⁹-THC by females during adolescence may produce long-term deficits in complex behavioral processes such as learning, and these deficits may be affected by the presence of ovarian hormones. To assess this possibility, 40 injections of saline or 5.6 mg/kg of Δ⁹-THC were administered i.p. daily during adolescence to gonadally intact or ovariectomized (OVX) female rats, yielding four treatment groups (intact/saline, intact/THC, OVX/saline, and OVX/ THC). Δ⁹-THC (0.56-10 mg/kg) was then re-administered to each of the four groups during adulthood to examine their sensitivity to its disruptive effects. The behavioral task required adult subjects to both learn (acquisition component) different response sequences and repeat a known response sequence (performance component) daily. During baseline (no injection) and control (saline injection) sessions, OVX subjects had significantly higher response rates and lower percentages of error in both behavioral components than the intact groups irrespective of saline or Δ⁹-THC administration during adolescence; the intact group that received Δ⁹-THC had the lowest response rates in each component. Upon re-administration of Δ⁹-THC, the groups that received adolescent ovariectomy alone, adolescent Δ⁹-THC administration alone, or both treatments were found to be less sensitive to the rate-decreasing effects, and more sensitive to the error-increasing effects of Δ⁹-THC than the control group (i.e. intact subjects that received saline during adolescence). Neurochemical analyses of the brains from each adolescent-treated group indicated that there were also persistent effects on cannabinoid type-1 (CB-1) receptor levels in the hippocampus and striatum that depended on the brain region and the presence of ovarian hormones. In addition, autoradiographic analyses of the brains from adolescent-treated, but behaviorally naïve, subjects indicated that ovariectomy and Δ⁹-THC administration produced effects on receptor coupling in some of the same brain regions. In summary, chronic administration of Δ⁹-THC during adolescence in female rats produced long-term effects on operant learning and performance tasks and on the cannabinoid system that were mediated by the presence of ovarian hormones, and that altered their sensitivity to Δ⁹-THC as adults.

Developmental consequences of perinatal cannabis exposure: behavioral and neuroendocrine effects in adult rodents

RATIONALE

Cannabis is the most commonly used illicit drug among pregnant women. Since the endocannabinoid system plays a crucial role in brain development, maternal exposure to cannabis derivatives might result in long-lasting neurobehavioral abnormalities in the exposed offspring. It is difficult to detect these effects, and their underlying neurobiological mechanisms, in clinical cohorts, because of their intrinsic methodological and interpretative issues.

OBJECTIVES

The present paper reviews relevant rodent studies examining the long-term behavioral consequences of exposure to cannabinoid compounds during pregnancy and/or lactation.

RESULTS

Maternal exposure to even low doses of cannabinoid compounds results in atypical locomotor activity, cognitive impairments, altered emotional behavior, and enhanced sensitivity to drugs of abuse in the adult rodent offspring. Some of the observed behavioral abnormalities might be related to alterations in stress hormone levels induced by maternal cannabis exposure.

CONCLUSIONS

There is increasing evidence from animal studies showing that cannabinoid drugs are neuroteratogens which induce enduring neurobehavioral abnormalities in the exposed offspring. Several preclinical findings reviewed in this paper are in line with clinical studies reporting hyperactivity, cognitive impairments and altered emotionality in humans exposed in utero to cannabis. Conversely, genetic, environmental and social factors could also influence the neurobiological effects of early cannabis exposure in humans.

Adolescent brain maturation, the endogenous cannabinoid system and the neurobiology of cannabis-induced schizophrenia

Cannabis use during adolescence increases the risk of developing psychotic disorders later in life. However, the neurobiological processes underlying this relationship are unknown. This review reports the results of a literature search comprising various neurobiological disciplines, ultimately converging into a model that might explain the neurobiology of cannabis-induced schizophrenia. The article briefly reviews current insights into brain development during adolescence. In particular, the role of the excitatory neurotransmitter glutamate in experience-dependent maturation of specific cortical circuitries is examined. The review also covers recent hypotheses regarding disturbances in strengthening and pruning of synaptic connections in the prefrontal cortex, and the link with latent psychotic disorders. In the present model, cannabis-induced schizophrenia is considered to be a distortion of normal late postnatal brain maturation. Distortion of glutamatergic transmission during critical periods may disturb prefrontal neurocircuitry in specific brain areas. Our model postulates that adolescent exposure to Δ9-tetrahydrocannabinol (THC), the primary psychoactive substance in cannabis, transiently disturbs physiological control of the endogenous cannabinoid system over glutamate and GABA release. As a result, THC may adversely affect adolescent experience-dependent maturation of neural circuitries within prefrontal cortical areas. Depending on dose, exact time window and duration of exposure, this may ultimately lead to the development of psychosis or schizophrenia. The proposed model provides testable hypotheses which can be addressed in future studies, including animal experiments, reanalysis of existing epidemiological data, and prospective epidemiological studies in which the role of the dose-time-effect relationship should be central.

GABA(A) receptor density is altered by cannabinoid treatment in the hippocampus of adult but not adolescent rats

Cannabinoids are known to induce transient psychotic symptoms and cognitive dysfunction in healthy individuals and contribute to trigger schizophrenia in vulnerable individuals, particularly during adolescence. Converging preclinical evidence suggests important interactions between cannabinoid and GABAergic systems. In the present study, we compared the effects of cannabinoid treatment on GABA(A) receptor binding in the brain of adolescent and adult rats. Adolescent (5 weeks old) and adult (10 weeks old) rats were treated with the synthetic cannabinoid HU210 (25, 50 or 100 microg/kg/day) or vehicle for 1, 4 or 14 days. Rats were sacrificed 24 h after the last injection and GABA(A) receptor density was measured in several brain regions using [(35)S]TBPS and in vitro autoradiography. Adolescent rats had higher numbers of GABA(A) receptors compared to adults. A 24% increase of binding in adult rats treated with 100 microg/kg HU210 for 14 days compared to controls was observed in the CA1 region of the hippocampus (16.1 versus 12.9 fmol/mg tissue equivalent, t=2.720, p<0.05). HU210 did not affect GABA(A) receptors in adolescent rats in any treatment regimen and in adult rats treated with HU210 for 1 or 4 days. These data suggest that long-term, high-dose treatment with HU210 increases GABA(A) receptors in the hippocampus of adult rats, changes that may interfere with associated hippocampal cognitive functions such as learning and memory. In addition, our results suggest that the adolescent brain does not display the same compensatory mechanisms that are activated in the adult brain following cannabinoid treatment.

The polarised life of the endocannabinoid system in CNS development

The spatiotemporal expression of cannabinoid receptors and endocannabinoid-metabolising enzymes during brain development guides major developmental processes including neurogenesis, cell differentiation, cell migration, neuronal specification and synaptogenesis.Endocannabinoids (eCBs) play an important role in fine-tuning neurotransmission and have recently been shown to play an important role in brain development. The spatiotemporal expression of cannabinoid receptors and endocannabinoid-metabolising enzymes during development guides major developmental processes including neurogenesis, cell differentiation, cell migration, neuronal specification and synaptogenesis. Furthermore, pharmacological experiments and transgenic animal models have shown the impact of disrupted eCB signalling on normal brain development and revealed the danger of both cannabis abuse and exposure to cannabinoid drugs during embryonic development, childhood and adolescence. In this review, we focus on the dynamic expression of eCB components and the physiological role eCBs play during brain development.

Protracted cannabinoid administration elicits antidepressant behavioral responses in rats: role of gender and noradrenergic transmission

Research has shown that enhancement of cannabinoid CB(1) receptor activity elicits an antidepressant-like response in the forced swim test (FST); however, the effects of chronic administration of cannabinoid agents in the FST are not well characterized. In Experiment 1, the CB(1) receptor agonist HU-210 (0.1 mg/kg) was administered for 10 days to male rats, following which animals were exposed to the FST. In Experiment 2, the same protocol was utilized; however, prior to the FST animals were co-treated with either prazosin (1 mg/kg; an alpha(1)-adrenoreceptor antagonist) or propranolol (2.5 mg/kg; a beta-adrenoreceptor antagonist). In Experiment 3, the same protocol was employed in both male and female rats, and the role of drug withdrawal was examined by administration of the CB(1) receptor antagonist AM251 (1 mg/kg) prior to the FST. Experiment 1 revealed that HU-210 administration evoked a reduction in immobility and increase in struggling that was identical to that produced by the antidepressant desipramine (10 mg/kg). Experiment 2 revealed that this effect was attenuated by both alpha- and beta-adrenoreceptor antagonists, suggesting noradrenergic involvement in this antidepressant-like profile. Experiment 3 demonstrated that HU-210 administration produced an antidepressant response in both males and females, which was attenuated by the induction of precipitated withdrawal. These results show that protracted administration of a CB(1) receptor agonist produces an antidepressant-like response in the FST in both sexes, which appears to involve the noradrenergic system.

Regulation of gene transcription and keratinocyte differentiation by anandamide

Anandamide (AEA) is a member of an endogenous class of lipid mediators, known as endocannabinoids, which are involved in various biological processes. In particular, AEA regulates cell growth, differentiation, and death. Accumulating evidence demonstrates that AEA controls also epidermal differentiation, one of the best characterized mechanisms of cell specialization. Indeed, the epidermis is a keratinized multistratified epithelium that functions as a barrier to protect the organism from dehydration, mechanical trauma, and microbial insults. Its function is established during embryogenesis and is maintained during the whole life span of the organism, through a complex and tightly controlled program, termed epidermal terminal differentiation (or cornification). Whereas the morphological changes that occur during cornification have been extensively studied, the molecular mechanisms that underlie this process remain poorly understood. In this chapter, we summarize current knowledge about the molecular regulation of proliferation and terminal differentiation in mammalian epidermis. In this context, we show that endocannabinoids are finely regulated by, and can interfere with, the differentiation program. In addition, we review the role of AEA in the control of cornification, and show that it occurs by maintaining a transcriptional repression of gene expression through increased DNA methylation.