Pharmacokinetic, behavioral, and brain activity effects of Δ9-tetrahydrocannabinol in adolescent male and female rats

Prenatal tetrahydrocannabinol and cannabidiol exposure produce sex-specific pathophysiological phenotypes in the adolescent prefrontal cortex and hippocampus

Clinical and preclinical evidence has demonstrated an increased risk for neuropsychiatric disorders following prenatal cannabinoid exposure. However, given the phytochemical complexity of cannabis, there is a need to understand how specific components of cannabis may contribute to these neurodevelopmental risks later in life. To investigate this, a rat model of prenatal cannabinoid exposure was utilized to examine the impacts of specific cannabis constituents (Δ9-tetrahydrocannabinol [THC]; cannabidiol [CBD]) alone and in combination on future neuropsychiatric liability in male and female offspring. Prenatal THC and CBD exposure were associated with low birth weight. At adolescence, offspring displayed sex-specific behavioural changes in anxiety, temporal order and social cognition, and sensorimotor gating. These phenotypes were associated with sex and treatment-specific neuronal and gene transcriptional alterations in the prefrontal cortex, and ventral hippocampus, regions where the endocannabinoid system is implicated in affective and cognitive development. Electrophysiology and RT-qPCR analysis in these regions implicated dysregulation of the endocannabinoid system and balance of excitatory and inhibitory signalling in the developmental consequences of prenatal cannabinoids. These findings reveal critical insights into how specific cannabinoids can differentially impact the developing fetal brains of males and females to enhance subsequent neuropsychiatric risk.

Changes in Immune-Related Biomarkers and Endocannabinoids as a Function of Frequency of Cannabis Use in People Living With and Without HIV

Background: Cannabis use is common among people living with HIV (PLWH). Some observational studies of PLWH have linked cannabis use to lower immune markers; however, this is yet to be confirmed. In addition, whether HIV affects the endogenous cannabinoid system has not been studied. Our objective was to examine changes in immune-related biomarkers and endocannabinoids as a function of cannabis use frequency in people living with and without HIV. Materials and Methods: Data were obtained from a longitudinal study of men who have sex with men living in Los Angeles with, or at risk for, HIV. By design, half were PLWH. Those eligible for the parent study were willing and able to return for follow-up every 6 months. Those eligible for inclusion in this study reported varying levels of current cannabis use at follow-up. Specifically, one visit corresponded to a period of daily use and another to a period of infrequent use (weekly, monthly, or less than monthly). Banked serum from all eligible participants was analyzed for immune-related biomarkers, endocannabinoids, and paracannabinoids. Results: The analysis included 36 men, 19 of whom were PLWH. PLWH reported greater lifetime methamphetamine or amphetamine use (68% vs. 0%) and current cigarette use (55% vs. 20%) than people without HIV. Serum levels of HIV-related immune biomarkers including tumor necrosis factor receptor 2 (TNFR2; p=0.013) and CD27 (p=0.004) were greater in PLWH, alongside lower anandamide (AEA) (F1,34=5.337, p=0.027) and oleoylethanolamide (OEA) (F1,34=8.222, p=0.007) levels relative to people without HIV. Frequency of cannabis use did not impact the serum analytes in our study. Conclusions: Higher levels of TNFR2 and CD27 and lower levels of AEA and OEA in PLWH underscore the role of the TNF/TNFR superfamily in HIV, while highlighting a new role for the enzymatic activity of fatty acid amide hydrolase (the enzyme that hydrolyzes AEA and OEA) in HIV. Findings that cannabis frequency did not impact the immune phenotype may not generalize to other populations of PLWH. Additional work is required to further clarify the relationship between immune markers and endocannabinoids as a function of cannabis use frequency in PLWH. ClinicalTrials.gov ID: NCT01201083.

Adolescent THC impacts on mPFC dopamine-mediated cognitive processes in male and female rats

Rationale

Adolescent cannabis use is linked to later-life changes in cognition, learning, and memory. Rodent experimental studies suggest Δ9-tetrahydrocannabinol (THC) influences development of circuits underlying these processes, especially in the prefrontal cortex, which matures during adolescence.

Objective

We determined how 14 daily THC injections (5mg/kg) during adolescence persistently impacts medial prefrontal cortex (mPFC) dopamine-dependent cognition.

Methods

In adult Long Evans rats treated as adolescents with THC (AdoTHC), we quantify performance on two mPFC dopamine-dependent reward-based tasks-strategy set shifting and probabilistic discounting. We also determined how acute dopamine augmentation with amphetamine (0, 0.25, 0.5 mg/kg), or specific chemogenetic stimulation of ventral tegmental area (VTA) dopamine neurons and their projections to mPFC impacts probabilistic discounting.

Results

AdoTHC sex-dependently impacts acquisition of cue-guided instrumental reward seeking, but has minimal effects on set-shifting or probabilistic discounting in either sex. When we challenged dopamine circuits acutely with amphetamine during probabilistic discounting, we found reduced discounting of improbable reward options, with AdoTHC rats being more sensitive to these effects than controls. In contrast, neither acute chemogenetic stimulation of VTA dopamine neurons nor pathway-specific chemogenetic stimulation of their projection to mPFC impacted probabilistic discounting in control rats, although stimulation of this cortical dopamine projection slightly disrupted choices in AdoTHC rats.

Conclusions

These studies confirm a marked specificity in the cognitive processes impacted by AdoTHC exposure. They also suggest that some persistent AdoTHC effects may alter amphetamine-induced cognitive changes in a manner independent of VTA dopamine projections to mPFC, or via alterations of non-VTA dopamine neurons.

Neural circuit basis of adolescent THC-induced potentiation of opioid responses in adult mice

Use of one drug of abuse typically influences the behavioral response to other drugs, either administered at the same time or a subsequent time point. The nature of the drugs being used, as well as the timing and dosing, also influence how these drugs interact. Here, we tested the effects of adolescent THC exposure on the development of morphine-induced behavioral adaptations following repeated morphine exposure during adulthood. We found that adolescent THC administration impacted morphine-induced behaviors across several dimensions, including potentiating reward and paradoxically impairing the development of morphine reward. We then mapped the whole-brain response to a reinstatement dose of morphine, finding that adolescent THC administration led to increased activity in the basal ganglia and increased functional connectivity between frontal cortical regions and the ventral tegmental area. Last, we show using rabies virus-based circuit mapping that adolescent THC exposure triggers a long-lasting elevation in connectivity from the frontal cortex regions onto ventral tegmental dopamine cells that has the potential to influence dopaminergic response to morphine administration during adulthood. Our study adds to the rich literature on the interaction between drugs of abuse and provides potential circuit substates by which adolescent THC exposure influences responses to morphine later in life.

A Sensitive Ultrahigh-Performance Liquid Chromatography/Tandem Mass Spectrometry Method for the Simultaneous Analysis of Phytocannabinoids and Endocannabinoids in Plasma and Brain

Introduction: Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are major chemical constituents of cannabis, which may interact either directly or indirectly with the endocannabinoid and endocannabinoid-like ("paracannabinoid") systems, two lipid-based signaling complexes that play important roles in physiology. Legislative changes emphasize the need to understand how THC and CBD might impact endocannabinoid and paracannabinoid signaling, and to develop analytical approaches to study such impact. In this study, we describe a sensitive and accurate method for the simultaneous quantification of THC, its main oxidative metabolites [11-hydroxy-Δ9-THC (11-OH-THC) and 11-nor-9-carboxy-Δ9-THC (11-COOH-THC)], CBD, and a representative set of endocannabinoid [anandamide and 2-arachidonoyl-sn-glycerol (2-AG)] and paracannabinoid [palmitoylethanolamide (PEA) and oleoylethanolamide (OEA)] compounds. Analyte separation relies on the temperature-dependent shape selectivity properties of polymerically bonded C18 stationary phases. Materials and Methods: Analytes are extracted from tissues using acetonitrile precipitation followed by phospholipid removal. The ultrahigh-performance liquid chromatography/tandem mass spectrometry protocol utilizes a commercially available C18 polymeric-bonded phase column and a simple gradient elution system. Results: Ten-point calibration curves show excellent linearity (R2>0.99) over a wide range of analyte concentrations (0.02-500 ng/mL). Lowest limits of quantification are 0.05 ng/mL for anandamide, 0.1 ng/mL for 11-OH-THC and OEA, 0.2 ng/mL for THC and CBD, 0.5 ng/mL for 11-COOH-THC, 1.0 ng/mL for 2-AG, and 2.0 ng/mL for PEA. The lowest limits of detection are 0.02 ng/mL for anandamide, 0.05 ng/mL for 11-OH-THC and OEA, 0.1 ng/mL for THC and CBD, 0.2 ng/mL for 11-COOH-THC, 0.5 ng/mL for 2-AG, and 1.0 ng/mL for PEA. Conclusions: An application of the method is presented, which showed that phytocannabinoid administration elevates endocannabinoid levels in plasma and brain of adolescent male and female mice.

Effects of acute Δ9-tetrahydrocannabinol on behavior and the endocannabinoid system in HIV-1 Tat transgenic female and male mice

Cannabis use is highly prevalent especially among people living with HIV (PLWH). Activation of the anti-inflammatory and neuroprotective endocannabinoid system by phytocannabinoids, i.e. Δ9-tetrahydrocannabinol (THC), has been proposed to reduce HIV symptoms. However, THC's effects on HIV-related memory deficits are unclear. Using HIV-1 Tat transgenic mice, the current study investigates acute THC effects on various behavioral outcomes and the endocannabinoid system. For the rodent tetrad model, THC doses (1, 3, 10 mg/kg) induced known antinociceptive effects, with Tat induction increasing antinociceptive THC effects at 3 and 10 mg/kg doses. Only minor or no effects were noted for acute THC on body temperature, locomotor activity, and coordination. Increased anxiety-like behavior was found for females compared to males, but acute THC had no effect on anxiety. Object recognition memory was diminished by acute THC in Tat(-) females but not Tat(+) females, without affecting males. The endocannabinoid system and related lipids were not affected by acute THC, except for THC-induced decreases in CB1R protein expression levels in the spinal cord of Tat(-) mice. Female sex and Tat induction was associated with elevated 2-AG, AEA, AA, CB1R, CB2R, FAAH and/or MAGL expression in various brain regions. Further, AEA levels in the prefrontal cortex of Tat(+) females were negatively associated with object recognition memory. Overall, findings indicate that acute THC exerts differential effects on antinociception and memory, dependent on sex and HIV Tat expression, potentially in relation to an altered endocannabinoid system, which may be of relevance in view of potential cannabis-based treatment options for PLWH.

Frequent low-impact exposure to THC during adolescence causes persistent sexually dimorphic alterations in the response to viral infection in mice

Adolescent exposure to Δ9-tetrahydrocannabinol (THC) has enduring effects on energy metabolism and immune function. Prior work showed that daily administration of a low-impact dose of THC (5 mg/kg, intraperitoneal) during adolescence alters transcription in adult microglia and disrupts their response to bacterial endotoxin or social stress. To explore the lasting impact of adolescent THC exposure on the brain's reaction to viral infection, we administered THC (5 mg/kg, intraperitoneal) in male and female mice once daily on postnatal day (PND) 30-43. When the mice reached adulthood (PND 70), we challenged them with the viral mimic, polyinosinic acid:polycytidylic acid [Poly(I:C)], and assessed sickness behavior (motor activity, body temperature) and whole brain gene transcription. Poly(I:C) caused an elevation in body temperature which was lessened by prior THC exposure in female but not male mice. Adolescent THC exposure did not affect the locomotor response to Poly(I:C) in either sex. Transcriptomic analyses showed that Poly(I:C) produced a substantial upregulation of immune-related genes in the brain, which was decreased by THC in females. Additionally, the viral mimic caused a male-selective downregulation in transcription of genes involved in neurodevelopment and synaptic transmission, which was abrogated by adolescent THC treatment. The results indicate that Poly(I:C) produces complex transcriptional alterations in the mouse brain, which are sexually dimorphic and differentially affected by early-life THC exposure. In particular, adolescent THC dampens the brain's antiviral response to Poly(I:C) in female mice and prevents the transcriptional downregulation of neuron-related genes caused by the viral mimic in male mice.

Δ9-tetrahydrocannabinol discrimination: Effects of route of administration in mice

Background

Route of administration is an important pharmacokinetic variable in development of translationally relevant preclinical models. Humans primarily administer cannabis through smoking, vaping, and edibles. In contrast, preclinical research has historically utilized injected Δ9-tetrahydrocannabinol (THC). The present study sought to examine how route of administration affected the potency and time course of THC's discriminative stimulus properties.

Methods

Adult female and male C57BL/6 mice were trained to discriminate intraperitoneal (i.p.) THC from vehicle in a drug discrimination procedure. After discrimination was acquired, a dose-effect curve was determined for i.p., oral (p.o.), subcutaneous (s.c.), and aerosolized THC. Subsequently, the time course of effects of each route of administration was determined.

Results

THC administered i.p., p.o., s.c., or via aerosolization fully substituted for i.p. THC. The potency of THC's psychoactive effects was similar for i.p., p.o., and s.c., except that THC was more potent when administered s.c. vs p.o. in females. All routes of administration had a similar potency in both sexes. The duration of THC's psychoactive effects was similar across i.p., s.c., and p.o. routes of administration, whereas aerosolized THC produced a faster onset and shorter duration of effects compared to the other routes.

Conclusion

THC administered via multiple routes of administration, including those commonly used in preclinical research (i.p. and s.c.) and more translationally relevant routes (aerosol and p.o.), produced THC-like discriminative stimulus effects in mice trained to discriminate i.p. THC. More precise predictions of THC's effects in humans may result from use of these translationally relevant routes of administration.

Sex and Gender Differences in Simultaneous Alcohol and Cannabis Use: a Narrative Review

Purpose of Review

The aim is to review recent literature on sex and gender differences in patterns of use, motives, pharmacological effects, and consequences of simultaneous alcohol and cannabis use (SAC).

Recent Findings

Men engage in SAC more frequently than women. Women may have more substance-specific motives for use, while men tend to consistently endorse social/enhancement motives for both alcohol and cannabis. Regarding pharmacological effects, women experience the same subjective effects as men do at lower levels of use, with some evidence that women modulate cannabis use during simultaneous use episodes to avoid greater subjective intoxication. Finally, women appear more vulnerable to experiencing a range of positive and negative consequences from SAC relative to men.

Summary

Research has identified several important sex/gender differences in SAC and its correlates and consequences. However, research has primarily focused on white and cisgender populations, with a need for more research among racial/ethnic and gender minorities.

The Effect of Route of Administration and Vehicle on the Pharmacokinetics of THC and CBD in Adult, Neonate, and Breastfed Sprague-Dawley Rats

Introduction: Basic pharmacokinetic (PK) and pharmacodynamic models of the phytocannabinoids Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are critical for developing translational models of exposure and toxicity. The neonatal period is a particularly important time to study the effects of cannabinoids, yet there are few studies of cannabinoid PKs by different routes such as direct injection or breast milk ingestion. To study this question, we have developed a translationally relevant rodent model of perinatal cannabinoid administration by measuring plasma levels of THC and CBD after different routes and preparations of these drugs. Materials and Methods: Adult animals and pups were injected with THC or CBD either intraperitoneally or subcutaneously, and plasma was analyzed by liquid chromatography-tandem mass spectrometry to measure cannabinoid levels collected at specified intervals. We also tested the effect of preparation of the drug using an oil-based vehicle (sesame oil) and an aqueous vehicle (Tween). Finally, we measured the plasma levels of cannabinoids in neonatal pups that were transmitted through breast milk after intraperitoneal injection to nursing dams. Results: We observed differences in the PK profiles of cannabinoids in adults and neonatal pups that were dependent on the route of administration and type of vehicle. Cannabinoids prepared in aqueous vehicle, injected intraperitoneally, resulted in a high peak in plasma concentration, which rapidly decreased. In contrast, subcutaneous injections using sesame oil as a vehicle resulted in a slow rise and low plateau in plasma concentration. Intraperitoneal injections with sesame oil as a vehicle resulted in a slower rise compared with aqueous vehicle, but an earlier and higher peak compared with subcutaneous injection. Finally, the levels of THC and CBD that were similar to direct subcutaneous injections were measured in the plasma of pups nursing from intraperitoneally injected dams. Conclusions: The route of administration and the preparation of the drug have important and significant effects on the PK profiles of THC and CBD in rats. These results can be used to create different clinically relevant exposure paradigms in pups and adults, such as short high-dose exposure or a low-chronic exposure, each of which might have significant and varying effects on development.

Pharmacokinetics of delta-9-tetrahydrocannabinol following acute cannabis smoke exposure in mice; effects of sex, age, and strain

Increased use of cannabis and cannabinoids for recreational and medical purposes has led to a growth in research on their effects in animal models. The majority of this work has employed cannabinoid injections; however, smoking remains the most common route of cannabis consumption. To better model real-world cannabis use, we exposed mice to cannabis smoke to establish the pharmacokinetics of Δ9THC and its metabolites in plasma and brain. To determine the time course of Δ9THC and two major metabolites [11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (11-COOH-THC)], male and female C57BL/6J mice were exposed to smoke from sequentially burning 5 cannabis cigarettes. Following smoke exposure, trunk blood and brains were collected at 6 time points (10-240 min). Plasma and brain homogenates were analyzed for Δ9THC and metabolites using a validated ultraperformance liquid chromatography-tandem mass spectrometry method. To assess effects of age, sex, and mouse strain, we exposed mice of four strains (C57BL/6J, FVB, Swiss Webster, and 129S6/SvEv, aged 4-24 months) to cannabis using the same smoke regimen. Samples were collected 10 and 40 min following exposure. Lastly, to assess effects of dose, C57BL/6J mice were exposed to smoke from burning 3 or 5 cannabis cigarettes, with samples collected 40 min following exposure. The pharmacokinetic study revealed that maximum plasma Δ9THC concentrations (Cmax) were achieved at 10 and 40 min for males and females, respectively, while Cmax for brain Δ9THC was observed at 20 and 40 min for males and females, respectively. There were no age or strain differences in plasma Δ9THC concentrations at 10 or 40 min; however, 129S6/SvEv mice had significantly higher brain Δ9THC concentrations than FVB mice. Additionally, 3 cigarettes produced significantly lower plasma 11-COOH-THC concentrations compared to 5 cigarettes, although dose differences were not evident in plasma or brain concentrations of Δ9THC or 11-OH-THC. Across all experiments, females had higher levels of 11-COOH-THC in plasma compared to males. The results reveal robust sex differences in Δ9THC pharmacokinetics, and lay the groundwork for future studies using mice to model the pharmacodynamics of smoked cannabis.

Experience with dronabinol consumption facilitated a stimulant effect of alcohol and affected alcohol-related changes in frontal cortical endocannabinoid levels in male rats

Combined use of cannabis and alcohol is common in adolescents. However, the extent to which such polydrug exposure affects the brain and behaviors remains under-investigated in preclinical studies. This study tested the hypothesis that combined exposure of Δ-9-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, and alcohol will have additive effects on cognitive impairments and altered endocannabinoid levels in the hippocampus and frontal cortex. Male Long Evans rats were provided with daily access to cookies laced with oil or dronabinol, a synthetic THC, during adolescence. Three days after discontinuation of edible THC, the effect of orally administered 3 g/kg alcohol on Barnes maze performance was assessed. The results showed that experience with edible THC facilitated the occurrence of increased moving speed on the maze induced by repeated alcohol administration. However, contrasting to the hypothesis, the combined THC and alcohol exposure did not lead to additive deficits in learning and memory on the Barnes maze. While little effect on endocannabinoid levels was observed in the hippocampus, acute abstinence from alcohol significantly reduced endocannabinoid levels in the frontal cortex. In particular, reduction of N-oleoyl ethanolamine (OEA) and N-stearoyl ethanolamine (SEA) were robust and had an interactive effect with discontinuation from edible THC. These findings add to the scarce literature on THC and alcohol associated changes in endocannabinoid levels and provide insights to future investigations on the roles of OEA and SEA on physiology and behaviors following THC and alcohol co-exposure during adolescence.

Dose mediates the protracted effects of adolescent THC exposure on reward and stress reactivity in males relevant to perturbation of the basolateral amygdala transcriptome

Despite the belief that cannabis is relatively harmless, exposure during adolescence is associated with increased risk of developing several psychopathologies in adulthood. In addition to the high levels of use amongst teenagers, the potency of ∆-9-tetrahydrocannabinol (THC) has increased more than fourfold compared to even twenty years ago, and it is unclear whether potency influences the presentation of THC-induced behaviors. Expanded knowledge about the impact of adolescent THC exposure, especially high dose, is important to delineating neural networks and molecular mechanisms underlying psychiatric risk. Here, we observed that repeated exposure to low (1.5 mg/kg) and high (5 mg/kg) doses of THC during adolescence in male rats produced divergent effects on behavior in adulthood. Whereas low dose rats showed greater sensitivity to reward devaluation and also self-administered more heroin, high dose animals were significantly more reactive to social isolation stress. RNA sequencing of the basolateral amygdala, a region linked to reward processing and stress, revealed significant perturbations in transcripts and gene networks related to synaptic plasticity and HPA axis that were distinct to THC dose as well as stress. In silico single-cell deconvolution of the RNAseq data revealed a significant reduction of astrocyte-specific genes related to glutamate regulation in stressed high dose animals, a result paired anatomically with greater astrocyte-to-neuron ratios and hypotrophic astrocytes. These findings emphasize the importance of dose and behavioral state on the presentation of THC-related behavioral phenotypes in adulthood and dysregulation of astrocytes as an interface for the protracted effects of high dose THC and subsequent stress sensitivity.

Chronic Δ9-tetrahydrocannabinol treatment has dose-dependent effects on open field exploratory behavior and [3H] SR141716A receptor binding in the rat brain

AIMS

Acute and chronic Δ⁹-THC exposure paradigms affect the body differently. More must be known about the impact of chronic Δ⁹-THC on cannabinoid-1 (CB1R) and mu-opioid (MOR) receptor levels in the brain. The present study examined chronic Δ⁹-THC's effects on CB1R and MOR levels and locomotor activity.

MAIN METHODS

Adolescent Sprague-Dawley rats were given daily intraperitoneal injections of Δ⁹-THC [0.75mg/kg (low dose or LD) or 2.0 mg/kg (high dose or HD)] or vehicle for 24 days, and locomotion in the open field was tested after the first and fourth weeks of chronic Δ⁹-THC exposure. Brains were harvested at the end of treatment. [³H] SR141716A and [³H] DAMGO autoradiography assessed CB1R and MOR levels, respectively.

KEY FINDINGS

Relative to each other, chronic HD rats showed reduced vertical plane (VP) entries and time, while LD rats had increased VP entries and time for locomotion, as assessed by open-field testing; no effects were found relative to the control. Autoradiography analyses showed that HD Δ⁹-THC significantly decreased CB1R binding relative to LD Δ⁹-THC in the cingulate (33%), primary motor (42%), secondary motor (33%) somatosensory (38%), rhinal (38%), and auditory (50%) cortices; LD Δ⁹-THC rats displayed elevated binding in the primary motor (33% increase) and hypothalamic (33 % increase) regions compared with controls. No significant differences were observed in MOR binding for the LD or HD compared to the control.

SIGNIFICANCE

These results demonstrate that chronic Δ⁹-THC dose-dependently altered CB1R levels throughout the brain and locomotor activity in the open field.

Adolescent exposure to the Spice/K2 cannabinoid JWH-018 impairs sensorimotor gating and alters cortical perineuronal nets in a sex-dependent manner

The consumption of synthetic cannabinoids during adolescence is reported to be a risk factor for the appearance of psychiatric disorders later in life. JWH-018 was identified as one of the primary psychoactive components present in Spice/K2 preparations. This study evaluated the short- and long-term consequences of exposure to JWH-018 during the adolescence in anxiety-like behavior, fear extinction, and sensorimotor gating in male and female mice. Alterations in anxiety varied depending on the time interval between treatment and behavioral analysis along with sex, while no changes were observed in the extinction of fear memory. A decrease in prepulse inhibition of the startle reflex was revealed in male, but not female, mice at short- and long-term. This behavioral disturbance was associated with a reduction in the number of perineuronal nets in the prelimbic and infralimbic regions of the prefrontal cortex in the short-term. Furthermore, adolescent exposure to JWH-018 induced an activation of microglia and astrocytes in the prefrontal cortex of male mice at both time intervals. A transitory decrease in the expression of GAD67 and CB2 cannabinoid receptors in the prefrontal cortex was also found in male mice exposed to JWH-018. These data reveal that the treatment with JWH-018 during the adolescence leads to long-lasting neurobiological changes related to psychotic-like symptoms, which were sex-dependent.

Women are Taking the Hit: Examining the Unique Consequences of Cannabis Use Across the Female Lifespan

Cannabis use has risen dramatically in recent years due to global decriminalization and a resurgence in the interest of potential therapeutic benefits. While emerging research is shaping our understanding of the benefits and harms of cannabis, there remains a paucity of data specifically focused on how cannabis affects the female population. The female experience of cannabis use is unique, both in the societal context and because of the biological ramifications. This is increasingly important given the rise in cannabis potency, as well as the implications this has for the prevalence of Cannabis Use Disorder (CUD). Therefore, this scoping review aims to discuss the prevalence of cannabis use and CUD in women throughout their lifespan and provide a balanced prospective on the positive and negative consequences of cannabis use. In doing so, this review will highlight the necessity for continued research that goes beyond sex differences.

Long-term effects of THC exposure on reward learning and motivated behavior in adolescent and adult male rats

RATIONALE

The endocannabinoid system makes critical contributions to reward processing, motivation, and behavioral control. Repeated exposure to THC or other cannabinoid drugs can cause persistent adaptions in the endocannabinoid system and associated neural circuitry. It remains unclear how such treatments affect the way rewards are processed and pursued.

OBJECTIVE AND METHODS

We examined if repeated THC exposure (5 mg/kg/day for 14 days) during adolescence or adulthood led to long-term changes in rats' capacity to flexibly encode and use action-outcome associations for goal-directed decision making. Effects on hedonic feeding and progressive ratio responding were also assessed.

RESULTS

THC exposure had no effect on rats' ability to flexibly select actions following reward devaluation. However, instrumental contingency degradation learning, which involves avoiding an action that is unnecessary for reward delivery, was augmented in rats with a history of adult but not adolescent THC exposure. THC-exposed rats also displayed more vigorous instrumental behavior in this study, suggesting a motivational enhancement. A separate experiment found that while THC exposure had no effect on hedonic feeding behavior, it increased rats' willingness to work for food on a progressive ratio schedule, an effect that was more pronounced when THC was administered to adults. Adolescent and adult THC exposure had opposing effects on the CB1 receptor dependence of progressive ratio performance, decreasing and increasing sensitivity to rimonabant-induced behavioral suppression, respectively.

CONCLUSIONS

Our findings reveal that exposure to a translationally relevant THC exposure regimen induces long-lasting, age-dependent alterations in cognitive and motivational processes that regulate the pursuit of rewards.

D2/3 Agonist during Learning Potentiates Cued Risky Choice

Impulse control and/or gambling disorders can be triggered by dopamine agonist therapies used to treat Parkinson's disease, but the cognitive and neurobiological mechanisms underlying these adverse effects are unknown. Recent data show that adding win-paired sound and light cues to the rat gambling task (rGT) potentiates risky decision-making and impulsivity via the dopamine system, and that changing dopaminergic tone has a greater influence on behavior while subjects are learning task contingencies. Dopamine agonist therapy may therefore be potentiating risk-taking by amplifying the behavioral impact of gambling-related cues on novel behavior. Here, we show that ropinirole treatment in male rats transiently increased motor impulsivity but robustly and progressively increased choice of the high-risk/high-reward options when administered during acquisition of the cued but not uncued rGT. Early in training, ropinirole increased win-stay behavior after large unlikely wins on the cued rGT, indicative of enhanced model-free learning, which mediated the drug's effect on later risk preference. Ex vivo cFos imaging showed that both chronic ropinirole and the addition of win-paired cues suppressed the activity of dopaminergic midbrain neurons. The ratio of midbrain:prefrontal cFos+ neurons was lower in animals with suboptimal choice patterns and tended to predict risk preference across all rats. Network analyses further suggested that ropinirole induced decoupling of the dopaminergic cells of the VTA and nucleus accumbens but only when win-paired cues were present. Frontostriatal activity uninformed by the endogenous dopaminergic teaching signal therefore appeared to perpetuate risky choice, and ropinirole exaggerated this disconnect in synergy with reward-paired cues.SIGNIFICANCE STATEMENT D2/3 receptor agonists, used to treat Parkinson's disease, can cause gambling disorder through an unknown mechanism. Ropinirole increased risky decision-making in rats, but only when wins were paired with casino-inspired sounds and lights. This was mediated by increased win-stay behavior after large unlikely wins early in learning, indicating enhanced model-free learning. cFos imaging showed that ropinirole suppressed activity of midbrain dopamine neurons, an effect that was mimicked by the addition of win-paired cues. The degree of risky choice rats exhibited was uniquely predicted by the ratio of midbrain dopamine:PFC activity. Depriving the PFC of the endogenous dopaminergic teaching signal may therefore drive risky decision-making on-task, and ropinirole acts synergistically with win-paired cues to amplify this.

Long-Term Outcomes of Adolescent THC Exposure on Translational Cognitive Measures in Adulthood in an Animal Model and Computational Assessment of Human Data

Importance

Although perceived as relatively harmless and nonaddictive, adolescent cannabis use significantly increases the likelihood of developing cannabis use disorder in adulthood, especially for high-potency cannabis. Risky decision-making is associated with chronic cannabis use, but given confounds of human studies, it remains unclear whether adolescent cannabis exposure and Δ9-tetrahydrocannabinol (THC) potency specifically predicts risky decision-making or influences cognitive response to the drug later in life.

Objective

To leverage a human data set of cannabis users and a rat model to evaluate the long-term outcomes of adolescent THC exposure on adult decision-making and impulse control.

Design, Setting, and Participants

This translational rat study tested the link between adolescent THC exposure and adulthood decision-making. A reanalysis of a previously published dataset of human chronic cannabis users was conducted to evaluate decision-making phenotypes. Computational modeling assessed the human and animal results in a single framework. Data were collected from 2017 to 2020 and analyzed from 2020 to 2022.

Main Outcomes and Measures

Decision-making was measured by the Iowa Gambling Task (IGT) and Rat Gambling Task (rGT). Impulse control was assessed in the rat model. Computational modeling was used to determine reward and punishment learning rates and learning strategy used by cannabis users and THC-exposed rats. Cell-specific molecular measures were conducted in the prefrontal cortex and amygdala.

Results

Of 37 participants, 24 (65%) were male, and the mean (SD) age was 33.0 (8.3) years. Chronic cannabis users (n = 22; mean [SE] IGT score, -5.182 [1.262]) showed disadvantageous decision-making compared with controls (n = 15; mean [SE] IGT score, 7.133 [2.687]; Cohen d = 1.436). Risky choice was associated with increased reward learning (mean [SE] IGT score: cannabis user, 0.170 [0.018]; control, 0.046 [0.008]; Cohen d = 1.895) and a strategy favoring exploration vs long-term gains (mean [SE] IGT score: cannabis user, 0.088 [0.012]; control, 0.020 [0.002]; Cohen d = 2.218). Rats exposed to high-dose THC but not low-dose THC during adolescence also showed increased risky decision-making (mean [SE] rGT score: vehicle, 46.17 [7.02]; low-dose THC, 69.45 [6.01]; high-dose THC, 21.97 [11.98]; Cohen d = 0.433) and elevated reward learning rates (mean [SE] rGT score: vehicle, 0.17 [0.01]; low-dose THC, 0.10 [0.01]; high-dose THC, 0.24 [0.06]; Cohen d = 1.541) during task acquisition. These animals were also uniquely susceptible to increased cognitive impairments after reexposure to THC in adulthood, which was correlated with even greater reward learning (r = -0.525; P < .001) and a shift in strategy (r = 0.502; P < .001), similar to results seen in human cannabis users. Molecular studies revealed that adolescent THC dose differentially affected cannabinoid-1 receptor messenger RNA expression in the prelimbic cortex and basolateral amygdala in a layer- and cell-specific manner. Further, astrocyte glial fibrillary acidic protein messenger RNA expression associated with cognitive deficits apparent with adult THC reexposure.

Conclusions and Relevance

In this translational study, high-dose adolescent THC exposure was associated with cognitive vulnerability in adulthood, especially with THC re-exposure. These data also suggest a link between astrocytes and cognition that altogether provides important insights regarding the neurobiological genesis of risky cannabis use that may help promote prevention and treatment efforts.

Nasal accumulation and metabolism of Δ9-tetrahydrocannabinol following aerosol ('vaping') administration in an adolescent rat model

Passive aerosol exposure to Δ9-tetrahydrocannabinol (THC) in laboratory animals results in faster onset of action and less extensive liver metabolism compared to most other administration routes and might thus provide an ecologically relevant model of human cannabis inhalation. Previous studies have, however, overlooked the possibility that rodents, as obligate nose breathers, may accumulate aerosolized THC in the nasal cavity, from where the drug might directly diffuse to the brain. To test this, we administered THC (ten 5-s puffs of 100 mg/mL of THC) to adolescent (31-day-old) Sprague-Dawley rats of both sexes. We used liquid chromatography/tandem mass spectrometry to quantify the drug and its first-pass metabolites - 11-hydroxy-Δ9-THC (11-OH-THC) and 11-nor-9-carboxy-Δ9-THC (11-COOH-THC) - in nasal mucosa, lungs, plasma, and brain (olfactory bulb and cerebellum) at various time points after exposure. Apparent maximal THC concentration and area under the curve were ∼5 times higher in nasal mucosa than in lungs and 50-80 times higher than in plasma. Concentrations of 11-OH-THC were also greater in nasal mucosa and lungs than other tissues, whereas 11-COOH-THC was consistently undetectable. Experiments with microsomal preparations confirmed local metabolism of THC into 11-OH-THC (not 11-COOH-THC) in nasal mucosa and lungs. Finally, whole-body exposure to THC deposited substantial amounts of THC (∼150 mg/g) on fur but suppressed post-exposure grooming in rats of both sexes. The results indicate that THC absorption and metabolism in nasal mucosa and lungs, but probably not gastrointestinal tract, contribute to the pharmacological effects of aerosolized THC in male and female rats.

Vaporized Delta-9-tetrahydrocannabinol Inhalation in Female Sprague Dawley Rats: A Pharmacokinetic and Behavioral Assessment

BACKGROUND

Delta-9-tetrahydrocannabinol (THC) is the main psychoactive component of cannabis. Historically, rodent studies examining the effects of THC have used intraperitoneal injection as the route of administration, heavily focusing on male subjects. However, human cannabis use is often through inhalation rather than injection.

OBJECTIVE

We sought to characterize the pharmacokinetic and phenotypic profile of acutely inhaled THC in female rats, compared to intraperitoneal injection, to identify any differences in exposure of THC between routes of administration.

METHODS

Adult female rats were administered THC via inhalation or intraperitoneal injection. Serum samples from multiple time points were analyzed for THC and metabolites 11-hydroxy-delta-9-tetrahydrocannabinol and 11-nor-9-carboxy-delta-9-tetrahydrocannabinol using ultra-performance liquid chromatography-tandem mass spectrometry. Rats were similarly treated for locomotor activity analysis.

RESULTS

Rats treated with 2 mg/kg THC intraperitoneally reached a maximum serum THC concentration of 107.7 ± 21.9 ng/mL. Multiple THC inhalation doses were also examined (0.25 mL of 40 or 160 mg/mL THC), achieving maximum concentrations of 43.3 ± 7.2 and 71.6 ± 22.5 ng/mL THC in serum, respectively. Significantly reduced vertical locomotor activity was observed in the lower inhaled dose of THC and the intraperitoneal injected THC dose compared to vehicle treatment.

CONCLUSION

This study established a simple rodent model of inhaled THC, demonstrating the pharmacokinetic and locomotor profile of acute THC inhalation, compared to an i.p. injected THC dose in female subjects. These results will help support future inhalation THC rat research which is especially important when researching behavior and neurochemical effects of inhaled THC as a model of human cannabis use.

Comparative Pharmacokinetics of Δ9-Tetrahydrocannabinol in Adolescent and Adult Male and Female Rats

Introduction: Studies in rodent models have shown that adolescent exposure to Δ9-THC, the psychotropic constituent of cannabis, produces long-lasting alterations in brain function and behavior. However, our understanding of how age and sex might influence the distribution and metabolism of THC in laboratory rodents is still incomplete. In the present report, we provide a comparative analysis of the pharmacokinetic (PK) properties of THC in adolescent and adult rats of both sexes, and outline several dissimilarities across these groups. Materials and Methods: A single (acute) or 2-week daily (subchronic) administration of THC (0.5 or 5 mg/kg, acute; 5 mg/kg, subchronic; intraperitoneal) was given to adolescent (33-day-old, acute; 30-44-day-old, subchronic) and young adult (70-day-old, acute only) male and female rats. THC and its first-pass metabolites-11-hydroxy-Δ9-THC (11-OH-THC) and 11-nor-9-carboxy-Δ9-THC (11-COOH-THC)-were quantified in plasma and brain tissue using a selective isotope-dilution liquid chromatography/tandem mass spectrometry assay. Changes in body temperature were measured using abdominally implanted microchips. Biotransformation of THC to its metabolites using freshly prepared liver microsomes was assessed. Results: At the acute 5 mg/kg dose, maximal plasma concentrations of THC were twice as high in adult than in adolescent rats. Conversely, in adults, brain concentrations and brain-to-plasma ratios for THC were substantially lower (25-50%) than those measured in adolescents. Similarly, plasma and brain concentrations of THC metabolites were higher in adolescent male rats compared with adult males. Interestingly, plasma and brain concentrations of the psychoactive THC metabolite 11-OH-THC were twofold to sevenfold higher in female animals of both ages compared with males. Moreover, liver microsomes from adolescent males and adolescent and adult females converted THC to 11-OH-THC twice as fast as adult male microsomes. A dose-dependent hypothermic response to THC was observed in females with 0.5 and 5 mg/kg THC, whereas only the highest dose elicited a response in males. Finally, subchronic administration of THC during adolescence did not significantly affect the drug's PK profile. Conclusions: The results reveal the existence of multiple age and sex differences in the distribution and metabolism of THC in rats, which might influence the pharmacological response to the drug.

A Meta-Analysis of fMRI Studies of Youth Cannabis Use: Alterations in Executive Control, Social Cognition/Emotion Processing, and Reward Processing in Cannabis Using Youth

Background: Adolescent cannabis use (CU) is associated with adverse health outcomes and may be increasing in response to changing cannabis laws. Recent imaging studies have identified differences in brain activity between adult CU and controls that are more prominent in early onset users. Whether these differences are present in adolescent CU and relate to age/developmental stage, sex, or cannabis exposure is unknown. Methods: A systematic review and subsequent effect-size seed-based d mapping (SDM) meta-analysis were conducted to examine differences in blood-oxygen-level-dependent (BOLD) response during fMRI studies between CU and non-using typically developing (TD) youth. Supplemental analyses investigated differences in BOLD signal in CU and TD youth as a function of sex, psychiatric comorbidity, and the dose and severity of cannabis exposure. Results: From 1371 citations, 45 fMRI studies were identified for inclusion in the SDM meta-analysis. These studies compared BOLD response contrasts in 1216 CU and 1486 non-using TD participants. In primary meta-analyses stratified by cognitive paradigms, CU (compared to TD) youth showed greater activation in the rostral medial prefrontal cortex (rmPFC) and decreased activation in the dorsal mPFC (dmPFC) and dorsal anterior cingulate cortex (dACC) during executive control and social cognition/emotion processing, respectively. In meta-regression analyses and subgroup meta-analyses, sex, cannabis use disorder (CUD) severity, and psychiatric comorbidity were correlated with brain activation differences between CU and TD youth in mPFC and insular cortical regions. Activation differences in the caudate, thalamus, insula, dmPFC/dACC, and precentral and postcentral gyri varied as a function of the length of abstinence. Conclusions: Using an SDM meta-analytic approach, this report identified differences in neuronal response between CU and TD youth during executive control, emotion processing, and reward processing in cortical and subcortical brain regions that varied as a function of sex, CUD severity, psychiatric comorbidity, and length of abstinence. Whether aberrant brain function in CU youth is attributable to common predispositional factors, cannabis-induced neuroadaptive changes, or both warrants further investigation.

Effects of endocannabinoid system modulation on social behaviour: A systematic review of animal studies

There is a clear link between psychiatric disorders and social behaviour, and evidence suggests the involvement of the endocannabinoid system (ECS). A systematic review of preclinical literature was conducted using MEDLINE (PubMed) and PsychINFO databases to examine whether pharmacological and/or genetic manipulations of the ECS alter social behaviours in wildtype (WT) animals or models of social impairment (SIM). Eighty studies were included. Risk of bias (RoB) was assessed using SYRCLE's RoB tool. While some variability was evident, studies most consistently found that direct cannabinoid receptor (CBR) agonism decreased social behaviours in WT animals, while indirect CBR activation via enzyme inhibition or gene-knockout increased social behaviours. Direct and, more consistently, indirect CBR activation reversed social deficits in SIM. These CBR-mediated effects were often sex- and developmental-phase-dependent and blocked by CBR antagonism. Overall, ECS enzyme inhibition may improve social behaviour in SIM, suggesting the potential usefulness of ECS enzyme inhibition as a therapeutic approach for social deficits. Future research should endeavour to elucidate ECS status in neuropsychiatric disorders characterized by social deficits.

Adolescent THC exposure: effects on pain-related, exploratory, and consummatory behaviors in adult male vs. female rats

RATIONALE

Adolescent cannabinoid exposure has been shown to alter cognitive, reward-related, and motor behaviors as well as mesocorticolimbic dopamine (DA) function in adult animals. Pain is also influenced by mesocorticolimbic DA function, but it is not known whether pain or cannabinoid analgesia in adults is altered by early exposure to cannabinoids.

OBJECTIVE

To determine whether adolescent Δ⁹-tetrahydrocannabinol (THC) exposure alters pain-related behaviors before and after induction of persistent inflammatory pain, and whether it influences antinociceptive of THC, in adult rats, and to compare the impact of adolescent THC exposure on pain to its effects on known DA-dependent behaviors such as exploration and consumption of a sweet solution.

METHODS

Vehicle or THC (2.5 to 10 mg/kg s.c.) was administered daily to male and female rats on post-natal day (PND) 30-43. In adulthood (PND 80-88), sensitivity to mechanical and thermal stimuli before and after intraplantar injection of complete Freund's adjuvant (CFA) was determined. Antinociceptive, exploratory, and consummatory effects of 2.0 mg/kg THC were then examined.

RESULTS

Adolescent THC exposure did not significantly alter adult sensitivity to non-noxious or noxious stimuli either before or after CFA injection, nor did it alter the antinociceptive effect of THC. In contrast, adolescent THC exposure altered adult exploratory and consummatory behaviors in a sex-dependent manner: when tested as adults, adolescent THC-treated males showed less hedonic drinking than adolescent vehicle-treated males, and females but not males that had been THC-exposed as adolescents showed reduced sensitivity to THC-induced suppression of activity and THC-induced hedonic drinking as adults.

CONCLUSIONS

Adolescent THC exposure that altered both exploratory and consummatory behaviors in adults did not alter pain-related behaviors either before or after induction of inflammatory pain, suggesting that cannabinoid exposure during adolescence is not likely to substantially alter pain or cannabinoid analgesia in adulthood.

Changes in brain structure and function following chronic exposure to inhaled vaporised cannabis during periadolescence in female and male mice: A multimodal MRI study

BACKGROUND AND AIMS

Social norms and legality surrounding the use of medical and recreational cannabis are changing rapidly. The prevalence of cannabis use in adolescence is increasing. The aim of this study was to assess any sex-based neurobiological effects of chronically inhaled, vaporised cannabis on adolescent female and male mice.

METHODS

Female and male mice were exposed daily to vaporised cannabis (10.3% Δ-9-tetrahydrocannabinol [THC] and 0.05% cannabidiol [CBD]) or placebo from postnatal day 23 to day 51. Following cessation of treatment, mice were examined for changes in brain structure and function using noninvasive multimodal magnetic resonance imaging (MRI). Data from voxel-based morphometry, diffusion weighted imaging and rest state functional connectivity were registered to and analysed with a 3D mouse atlas with 139 brain areas. Following imaging, mice were tested for their preference for a novel object.

RESULTS

The effects were sexually dimorphic with females showing a unique distribution and inverse correlation between measures of fractional anisotropy and apparent diffusion coefficient localised to the forebrain and hindbrain. In contrast males displayed significant increased functional coupling with the thalamus, hypothalamus and brainstem reticular activating system as compared with controls. Cannabis males also presented with altered hippocampal coupling and deficits in cognitive function.

CONCLUSION

Chronic exposure to inhaled vaporised cannabis had significant effects on brain structure and function in early adulthood corroborating much of the literature. Females presented with changes in grey matter microarchitecture, while males showed altered functional connectivity in hippocampal circuitry and deficits in object recognition.

Short communication: Tissue distribution of major cannabinoids following intraperitoneal injection in male rats

Currently, peripheral tissue distribution of cannabinoids after treatment is poorly understood. This pilot study sought to examine the early tissue distribution of major cannabinoids 30 minutes following an intraperitoneal injection of vehicle (1:9 Tween 80/SAL), and doses of THC (1 mg/kg) and CBD (5 mg/kg) that are feasible for human consumption in serum, adipose, brain, lung, liver, jejunum, and muscle of male Sprague-Dawley rats. The jejunum and adipose were most enriched in THC. Similarly, CBD was enriched in the jejunum and adipose but also the liver. In contrast, the brain had the lowest concentration of cannabinoids relative to other tissues. The liver had the greatest concentration of the THC metabolites, 11-OH-THC and COOH-THC, compared to all other tissues. Overall, these findings highlight broad tissue distribution and marked differences in tissue concentration not previously appreciated. Thus, as cannabinoid research continues to rapidly grow, consideration of the potential bioactive effects of these molecules in peripheral tissues is warranted in future studies.

Interaction of sex and cannabis in adult in vivo brain imaging studies: A systematic review

Cannabis has been shown to cause structural and functional neurocognitive changes in heavy users. Cannabis use initiation aligns with brain development trajectories; therefore, it is imperative that the potential neurological implications of cannabis use are understood. Males and females reach neurodevelopmental milestones at different rates making it necessary to consider biological sex in all cannabis and brain-based research. Through use of a systamatic review in accordance with PRISMA guidelines, we aimed to understand the interaction between biological sex and cannabis use on brain-based markers. In total, 18 articles containing a sex-based analysis of cannabis users were identified. While the majority of studies (n = 11) reported no sex by cannabis use interactions on brain-based markers, those that reported findings (n = 8) suggest females may be more susceptible to cannabis’ neurotoxic effects. Unfortunately, a large portion of the literature was excluded due to no sex-based analysis. In addition, studies that reported no sex differences often contained a reduced number of females which may result in some studies being underpowered for sex-based analyses, making it difficult to draw firm conclusions. Suggestions to improve cannabis and sex-based reseach are proposed.

Pharmacokinetics and central accumulation of delta-9-tetrahydrocannabinol (THC) and its bioactive metabolites are influenced by route of administration and sex in rats

Up to a third of North Americans report using cannabis in the prior month, most commonly through inhalation. Animal models that reflect human consumption are critical to study the impact of cannabis on brain and behaviour. Most animal studies to date utilize injection of delta-9-tetrahydrocannabinol (THC; primary psychoactive component of cannabis). THC injections produce markedly different physiological and behavioural effects than inhalation, likely due to distinctive pharmacokinetics. The current study directly examined if administration route (injection versus inhalation) alters metabolism and central accumulation of THC and metabolites over time. Adult male and female Sprague–Dawley rats received either an intraperitoneal injection or a 15-min session of inhaled exposure to THC. Blood and brains were collected at 15, 30, 60, 90 and 240-min post-exposure for analysis of THC and metabolites. Despite achieving comparable peak blood THC concentrations in both groups, our results indicate higher initial brain THC concentration following inhalation, whereas injection resulted in dramatically higher 11-OH-THC concentration, a potent THC metabolite, in blood and brain that increased over time. Our results provide evidence of different pharmacokinetic profiles following inhalation versus injection. Accordingly, administration route should be considered during data interpretation, and translational animal work should strongly consider using inhalation models.

Adolescent THC Treatment Does Not Potentiate the Behavioral Effects in Adulthood of Maternal Immune Activation

Both in utero exposure to maternal immune activation and cannabis use during adolescence have been associated with increased risk for the development of schizophrenia; however, whether these exposures exert synergistic effects on brain function is not known. In the present study, mild maternal immune activation (MIA) was elicited in mice with prenatal exposure to polyinosinic-polycytidylic acid (poly(I:C)), and ∆9-tetrahydrocannabinol (THC) was provided throughout adolescence in cereal (3 mg/kg/day for 5 days). Neither THC nor MIA pretreatments altered activity in assays used to characterize hyperdopaminergic states in adulthood: amphetamine hyperlocomotion and prepulse inhibition of the acoustic startle reflex. Adolescent THC treatment elicited deficits in spatial memory and enhanced spatial reversal learning in adult female mice in the Morris water maze, while exposure to MIA elicited female-specific deficits in fear extinction learning in adulthood. There were no effects in these assays in adult males, nor were there interactions between THC and MIA in adult females. While doses of poly(I:C) and THC were sufficient to elicit behavioral effects, particularly relating to cognitive performance in females, there was no evidence that adolescent THC exposure synergized with the risk imposed by MIA to worsen behavioral outcomes in adult mice of either sex.

Pharmacokinetic and pharmacodynamic properties of aerosolized ("vaped") THC in adolescent male and female rats

RATIONALE

Adolescent exposure to ∆9-tetrahydrocannabinol (THC), the psychotropic constituent of cannabis, might affect brain development, and in rodent models leads to long-term behavioral and physiological alterations. Yet, the basic pharmacology of this drug in adolescent rodents, especially when ingested via ecologically relevant routes like aerosol inhalation, commonly referred to as "vaping," is still poorly characterized. Moreover, sex differences exist in THC metabolism, kinetics, and behavioral effects, but these have not been rigorously examined after vapor dosing in adolescents.

OBJECTIVES

We investigated the pharmacokinetics and pharmacodynamics of aerosolized THC (30 min inhalation exposure, 25 or 100 mg/ml) in adolescent Wistar rats of both sexes.

METHODS

Liquid chromatography/mass spectrometry analysis of THC and its major metabolites was conducted on blood plasma and brain tissue at 5, 30, 60, and 120 min following a 30-min aerosol dosing session. Effects on activity in a novel environment for 120 min after aerosol, and temperature, were measured in separate rats.

RESULTS

We found sex-dependent differences in the pharmacokinetics of THC and its active (11-OH-THC) and inactive (11-COOH-THC) metabolites in the blood and brain, along with dose- and sex-dependent effects on anxiety-like and exploratory behaviors; namely, greater 11-OH-THC levels accompanied by greater behavioral effects in females at the low dose but similar hypothermic effects in both sexes at the high dose.

CONCLUSIONS

These results provide a benchmark for dosing adolescent rats with aerosolized (or "vaped") THC, which could facilitate adoption by other labs of this potentially human-relevant THC exposure model to understand cannabis effects on the developing brain.

The stoned age: Sex differences in the effects of adolescent cannabinoid exposure on prefrontal cortex structure and function in animal models

Cannabis is the most used drug during adolescence, which is a period of enhanced cortical plasticity and synaptic remodeling that supports behavioral, cognitive, and emotional maturity. In this chapter, we review preclinical studies indicating that adolescent exposure to cannabinoids has lasting effects on the morphology and synaptic organization of the prefrontal cortex and associated circuitry, which may lead to cognitive dysfunction later in life. Additionally, we reviewed sex differences in the effects of adolescent cannabinoid exposure with a focus on brain systems that support cognitive functioning. The body of evidence indicates enduring sex-specific effects in behavior and organization of corticolimbic circuitry, which appears to be influenced by species, strain, drug, route of administration, and window/pattern of drug exposure. Caution should be exercised when extrapolating these results to humans. Adopting models that more closely resemble human cannabis use will provide more translationally relevant data concerning the long-term effects of cannabis use on the adolescent brain.

A review of the effects of acute and chronic cannabinoid exposure on the stress response

While cannabis has been used for centuries for its stress-alleviating properties, the effects of acute and chronic cannabinoid exposure on responses to stress remain poorly understood. This review provides an overview of studies that measured stress-related endpoints following acute or chronic cannabinoid exposure in humans and animals. Acute cannabinoid exposure increases basal concentrations of stress hormones in rodents and humans and has dose-dependent effects on stress reactivity in humans and anxiety-like behavior in rodents. Chronic cannabis exposure is associated with dampened stress reactivity, a blunted cortisol awakening response (CAR), and flattened diurnal cortisol slope in humans. Sex differences in these effects remain underexamined, with limited evidence for sex differences in effects of cannabinoids on stress reactivity in rodents. Future research is needed to better understand sex differences in the effects of cannabis on the stress response, as well as downstream impacts on mental health and stress-related disorders.

Persistent Exposure to Δ9-Tetrahydrocannabinol during Adolescence Does Not Affect Nociceptive Responding in Adult Mice

Evidence suggests that Δ9-tetrahydrocannabinol (Δ9-THC), the intoxicating component of cannabis, causes enduring changes in the structure and function of adolescent brain circuits implicated in nociceptive responding. However, whether such changes might persistently disrupt nociceptive behaviors remains unknown. In the present study, we subjected C57BL6/J mice of both sexes to once-daily injections of Δ9-THC (5 mg-kg-1, i.p.) or vehicle throughout adolescence (PND 30-43) and, when the animals had reached adulthood (PND 70), assessed nociceptive behavior using the formalin and chronic constriction injury tests. We also investigated, using the tail immersion test, the antinociceptive effects of morphine and the development of tolerance to such effects. The results show that adolescent Δ9-THC exposure does not significantly impair nociceptive responding or morphine-related antinociception and tolerance. The findings suggest that frequent exposure to a moderate dose of Δ9-THC during adolescence does not permanently alter nociceptive circuits in male or female mice. SIGNIFICANCE STATEMENT: The endocannabinoid system serves critical functions in the central and peripheral nervous systems, including regulation of pain, and can be modified by prolonged exposure to the intoxicating constituent of cannabis, Δ9-tetrahydrocannabinol (Δ9-THC). This raises the possibility that regular use of Δ9-THC-containing cannabis during adolescence might cause changes in nociception that persist into adulthood. This study found that frequent early-life exposure to a moderate dose of Δ9-THC does not permanently alter nociceptive function in male or female mice.

Acute Delta 9-tetrahydrocannabinol administration differentially alters the hippocampal opioid system in adult female and male rats

Our prior studies demonstrated that the rat hippocampal opioid system can undergo sex-specific adaptations to external stimuli that can influence opioid-associated learning processes. This opioid system extensively overlaps with the cannabinoid system. Moreover, acute administration of Δ⁹ Tetrahydrocannabinoid (THC), the primary psychoactive constituent of cannabis, can alter cognitive behaviors that involve the hippocampus. Here, we use light and electron microscopic immunocytochemical methods to examine the effects of acute THC (5 mg/kg, i.p., 1 h) on mossy fiber Leu-Enkephalin (LEnk) levels and the distribution and phosphorylation levels of delta and mu opioid receptors (DORs and MORs, respectively) in CA3 pyramidal cells and parvalbumin dentate hilar interneurons of adult female and male Sprague-Dawley rats. In females with elevated estrogen states (proestrus/estrus stage), acute THC altered the opioid system so that it resembled that seen in vehicle-injected females with low estrogen states (diestrus) and males: (1) mossy fiber LEnk levels in CA2/3a decreased; (2) phosphorylated-DOR levels in CA2/3a pyramidal cells increased; and (3) phosphorylated-MOR levels increased in most CA3b laminae. In males, acute THC resulted in the internalization of MORs in parvalbumin-containing interneuron dendrites which would decrease disinhibition of granule cells. In both sexes, acute THC redistributed DORs to the near plasma membrane of CA3 pyramidal cell dendrites, however, the dendritic region varied with sex. Additionally, acute THC also resulted in a sex-specific redistribution of DORs within CA3 pyramidal cell dendrites which could differentially promote synaptic plasticity and/or opioid-associated learning processes in both females and males.

Female but not male rats show biphasic effects of low doses of Δ9-tetrahydrocannabinol on anxiety: can cannabidiol interfere with these effects?

Δ⁹-tetrahydrocannabinol (THC) is the main phytocannabinoid present in the Cannabis sativa. It can produce dose-dependent anxiolytic or anxiogenic effects in males. THC effects on anxiety have scarcely been studied in females, despite their higher prevalence of anxiety disorders. Cannabidiol, another phytocannabinoid, has been reported to attenuate anxiety and some THC-induced effects. The present study aimed to investigate the behavioral and neurochemical effects of THC administered alone or combined with CBD in naturally cycling female rats tested in the elevated plus-maze. Systemically administered THC produced biphasic effects in females, anxiolytic at low doses (0.075 or 0.1 mg/kg) and anxiogenic at a higher dose (1.0 mg/kg). No anxiety changes were observed in males treated with the same THC dose range. The anxiogenic effect of THC was prevented by co-administration of CBD (1.0 or 3.0 mg/kg). CBD (3.0 mg/kg) caused an anxiolytic effect. At a lower dose (1.0 mg/kg), it facilitated the anxiolytic effect of the low THC dose. The anxiogenic effect of THC was accompanied by increased dopamine levels in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc). In contrast, its anxiolytic effect was associated with increased mPFC serotonin concentrations. The anxiolytic effect of CBD was accompanied by increased mPFC serotonin turnover. Together, these results indicate that female rats are susceptible to the biphasic effects of low THC doses on anxiety. These effects could depend on mPFC and NAc dopaminergic and serotoninergic neurotransmissions. CBD could minimize potential THC high-dose side effects whereas enhancing the anxiolytic action of its low doses in females.

Endocannabinoids, cannabinoids and the regulation of anxiety

Cannabis has been used for hundreds of years, with its ability to dampen feelings of anxiety often reported as a primary reason for use. Only recently has the specific role cannabinoids play in anxiety been thoroughly investigated. Here we discuss the body of evidence describing how endocannabinoids and exogenous cannabinoids are capable of regulating the generation and termination of anxiety states. Disruption of the endogenous cannabinoid (eCB) system following genetic manipulation, pharmacological intervention or stress exposure reliably leads to the generation of an anxiety state. On the other hand, upregulation of eCB signaling is capable of alleviating anxiety-like behaviors in multiple paradigms. When considering exogenous cannabinoid administration, cannabinoid receptor 1 (CB1) agonists have a biphasic, dose-dependent effect on anxiety such that low doses are anxiolytic while high doses are anxiogenic, a phenomenon that is evident in both rodent models and humans. Translational studies investigating a loss of function mutation in the gene for fatty acid amide hydrolase, the enzyme responsible for metabolizing AEA, have also shown that AEA signaling regulates anxiety in humans. Taken together, evidence reviewed here has outlined a convincing argument for cannabinoids being powerful regulators of both the manifestation and amelioration of anxiety symptoms, and highlights the therapeutic potential of targeting the eCB system for the development of novel classes of anxiolytics. This article is part of the special issue on 'Cannabinoids'.

Combined nicotine and ethanol age-dependently alter neural and behavioral responses in male rats

Use of alcohol (EtOH) and nicotine (Nic) typically begins during adolescence. Smoking and drinking often occur together and lead to a higher consumption of alcohol. Although we have shown that Nic+EtOH is reinforcing in self-administration tests in adolescent male rats, whether Nic+EtOH affects other behaviors or neuronal activity in an age-dependent manner is unknown. To address this, adolescent and adult male rats were given intravenous injections of Nic (30 µg/kg)+EtOH (4 mg/kg) and evaluated for locomotor and anxiety-like behaviors. Regional neuronal activity, assessed by cFos mRNA expression, was measured and used to evaluate functional connectivity in limbic regions associated with anxiety and motivation. Nic+EtOH increased locomotor activity and was anxiolytic in adolescents, but not adults. The posterior ventral tegmental area (pVTA), a critical regulator of drug reward, was selectively activated by Nic+EtOH in adults, while activity in its target region, the NAc-shell, was decreased. Drug-induced alterations in functional connectivity were more extensive in adults than adolescents and may act to inhibit behavioral responses to Nic+EtOH that are seen in adolescence. Overall, our findings suggest that brief, low-dose exposure to Nic+EtOH produces marked, age-dependent changes in brain and behavior and that there may be an ongoing maturation of the pVTA during adolescence that allows increased sensitivity to Nic+EtOH's reinforcing, hyperlocomotor, and anxiolytic effects. Furthermore, this work provides a potential mechanism for high rates of co-use of nicotine and alcohol by teenagers: this drug combination is anxiolytic and recruits functional networks that are unique from protective, inhibitory networks recruited in the mature and adult brain.

Cannabis and synaptic reprogramming of the developing brain

Recent years have been transformational in regard to the perception of the health risks and benefits of cannabis with increased acceptance of use. This has unintended neurodevelopmental implications given the increased use of cannabis and the potent levels of Δ⁹-tetrahydrocannabinol today being consumed by pregnant women, young mothers and teens. In this Review, we provide an overview of the neurobiological effects of cannabinoid exposure during prenatal/perinatal and adolescent periods, in which the endogenous cannabinoid system plays a fundamental role in neurodevelopmental processes. We highlight impaired synaptic plasticity as characteristic of developmental exposure and the important contribution of epigenetic reprogramming that maintains the long-term impact into adulthood and across generations. Such epigenetic influence by its very nature being highly responsive to the environment also provides the potential to diminish neural perturbations associated with developmental cannabis exposure.

Cannabis: A Toxin-Producing Plant with Potential Therapeutic Uses

For thousands of years, Cannabis sativa has been utilized as a medicine and for recreational and spiritual purposes. Phytocannabinoids are a family of compounds that are found in the cannabis plant, which is known for its psychotogenic and euphoric effects; the main psychotropic constituent of cannabis is Δ9-tetrahydrocannabinol (Δ9-THC). The pharmacological effects of cannabinoids are a result of interactions between those compounds and cannabinoid receptors, CB1 and CB2, located in many parts of the human body. Cannabis is used as a therapeutic agent for treating pain and emesis. Some cannabinoids are clinically applied for treating chronic pain, particularly cancer and multiple sclerosis-associated pain, for appetite stimulation and anti-emesis in HIV/AIDS and cancer patients, and for spasticity treatment in multiple sclerosis and epilepsy patients. Medical cannabis varies from recreational cannabis in the chemical content of THC and cannabidiol (CBD), modes of administration, and safety. Despite the therapeutic effects of cannabis, exposure to high concentrations of THC, the main compound that is responsible for most of the intoxicating effects experienced by users, could lead to psychological events and adverse effects that affect almost all body systems, such as neurological (dizziness, drowsiness, seizures, coma, and others), ophthalmological (mydriasis and conjunctival hyperemia), cardiovascular (tachycardia and arterial hypertension), and gastrointestinal (nausea, vomiting, and thirst), mainly associated with recreational use. Cannabis toxicity in children is more concerning and can cause serious adverse effects such as acute neurological symptoms (stupor), lethargy, seizures, and even coma. More countries are legalizing the commercial production and sale of cannabis for medicinal use, and some for recreational use as well. Liberalization of cannabis laws has led to increased incidence of toxicity, hyperemesis syndrome, lung disease cardiovascular disease, reduced fertility, tolerance, and dependence with chronic prolonged use. This review focuses on the potential therapeutic effects of cannabis and cannabinoids, as well as the acute and chronic toxic effects of cannabis use on various body systems.

Unexpected Role of Physiological Estrogen in Acute Stress-Induced Memory Deficits

Stress may promote emotional and cognitive disturbances, which differ by sex. Adverse outcomes, including memory disturbances, are typically observed following chronic stress, but are now being recognized also after short events, including mass shootings, assault, or natural disasters, events that consist of concurrent multiple acute stresses (MAS). Prior work has established profound and enduring effects of MAS on memory in males. Here we examined the effects of MAS on female mice and probed the role of hormonal fluctuations during the estrous cycle on MAS-induced memory problems and the underlying brain network and cellular mechanisms. Female mice were impacted by MAS in an estrous cycle-dependent manner: MAS impaired hippocampus-dependent spatial memory in early-proestrous mice, characterized by high levels of estradiol, whereas memory of mice stressed during estrus (low estradiol) was spared. As spatial memory requires an intact dorsal hippocampal CA1, we examined synaptic integrity in mice stressed at different cycle phases and found a congruence of dendritic spine density and spatial memory deficits, with reduced spine density only in mice stressed during high estradiol cycle phases. Assessing MAS-induced activation of brain networks interconnected with hippocampus, we identified differential estrous cycle-dependent activation of memory- and stress-related regions, including the amygdala. Network analyses of the cross-correlation of fos expression among these regions uncovered functional connectivity that differentiated impaired mice from those not impaired by MAS. In conclusion, the estrous cycle modulates the impact of MAS on spatial memory, and fluctuating physiological levels of sex hormones may contribute to this effect.SIGNIFICANCE STATEMENT: Effects of stress on brain functions, including memory, are profound and sex-dependent. Acute stressors occurring simultaneously result in spatial memory impairments in males, but effects on females are unknown. Here we identified estrous cycle-dependent effects of such stresses on memory in females. Surprisingly, females with higher physiological estradiol experienced stress-induced memory impairment and a loss of underlying synapses. Memory- and stress-responsive brain regions interconnected with hippocampus were differentially activated across high and low estradiol mice, and predicted memory impairment. Thus, at functional, network, and cellular levels, physiological estradiol influences the effects of stress on memory in females, providing insight into mechanisms of prominent sex differences in stress-related memory disorders, such as post-traumatic stress disorder.