Cannabis containing equivalent concentrations of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) induces less state anxiety than THC-dominant cannabis.

RATIONALE: Delta-9-tetrahydrocannabinol (THC), an active component of cannabis, can cause anxiety in some users during intoxication. Cannabidiol (CBD), another constituent of cannabis, has anxiolytic properties suggesting that cannabis products containing CBD in addition to THC may produce less anxiety than THC-only products. Findings to date around this issue have been inconclusive and could conceivably depend on moderating factors such as baseline anxiety levels in users. OBJECTIVE: The present study examined whether anxiety following single doses of vaporised THC, CBD and THC/CBD might be explained by state and trait anxiety levels at baseline. METHODS: A placebo-controlled, randomised, within-subjects study including 26 healthy recreational cannabis users tested the effects of vaporised THC-dominant cannabis (13.75 mg THC), CBD-dominant cannabis (13.75 mg CBD), THC/CBD-equivalent cannabis (13.75 mg THC/13.75 mg CBD) and placebo cannabis on anxiety. Self-rated trait anxiety was assessed with the State-Trait Anxiety Inventory (STAI). State levels of anxiety were objectively assessed with a computer-based emotional Stroop task (EST) and subjectively rated with the STAI-state questionnaire and a visual analogue scale. RESULTS: Both THC and THC/CBD significantly increased self-rated state anxiety compared to placebo. State anxiety after THC/CBD was significantly lower than after THC alone. THC-induced anxiety was independent of anxiety at baseline. When baseline anxiety was low, CBD completely counteracted THC-induced anxiety; however, when baseline anxiety was high, CBD did not counteract THC-induced anxiety. There were no effects of any treatment condition on the EST. CONCLUSION: Overall, the study demonstrated that the THC/CBD-equivalent cannabis induces less state anxiety than THC-dominant cannabis.

Author Correction: Composition and Use of Cannabis Extracts for Childhood Epilepsy in the Australian Community.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Composition and Use of Cannabis Extracts for Childhood Epilepsy in the Australian Community.

Recent surveys suggest that many parents are using illicit cannabis extracts in the hope of managing seizures in their children with epilepsy. In the current Australian study we conducted semi-structured interviews with families of children with diverse forms of epilepsy to explore their attitudes towards and experiences with using cannabis extracts. This included current or previous users of cannabis extracts to treat their child's seizures (n = 41 families), and families who had never used (n = 24 families). For those using cannabis, extracts were analysed for cannabinoid content, with specific comparison of samples rated by families as "effective" versus those rated "ineffective". Results showed that children given cannabis extracts tended to have more severe epilepsy historically and had trialled more anticonvulsants than those who had never received cannabis extracts. There was high variability in the cannabinoid content and profile of cannabis extracts rated as "effective", with no clear differences between extracts perceived as "effective" and "ineffective". Contrary to family's expectations, most samples contained low concentrations of cannabidiol, while Δ9-tetrahydrocannabinol was present in nearly every sample. These findings highlight profound variation in the illicit cannabis extracts being currently used in Australia and warrant further investigations into the therapeutic value of cannabinoids in epilepsy.

The direct actions of cannabidiol and 2-arachidonoyl glycerol at GABAA receptors.

Cannabidiol (CBD) is a major non-intoxicating component of cannabis and possesses anti-epileptic, anxiolytic and anti-hyperalgesic properties. The mechanism of action of CBD in producing such effects remains unclear. Despite evidence that some endogenous and synthetic cannabinoids interact with GABAA receptors, no-one has yet investigated the effects of CBD. Here we used two-electrode voltage clamp electrophysiology to compare the actions of CBD with those of the major central endocannabinoid, 2-arachidonoyl glycerol (2-AG) on human recombinant GABAA receptors (synaptic α1-6ßγ2 and extrasynaptic α4ß2δ) expressed on Xenopus oocytes. CBD and 2-AG were positive allosteric modulators at α1-6ßγ2 receptors, with low micromolar potencies. The maximal level of enhancement seen with either CBD or 2-AG were on α2-containing GABAA receptor subtypes, with approximately a 4-fold enhancement of the GABA EC5 evoked current, more than twice the potentiation seen with other α-subunit receptor combinations. Further we observed ß-subunit selectivity, whereby modulatory activity was higher at ß2/ß3 over ß1 subunits. The ß1-subunit homologous mutant ß2(V436T) substantially diminished the efficacy of both drugs to a third of that obtained with wild-type ß2 subunit combinations, but without changing potency. The potency of CBD increased and efficacy preserved in binary α1/α2ß2 receptors indicating that their effects do not involve the classic benzodiazepine site. Exploration of extrasynaptic α4ß2δ receptors revealed that both compounds enhanced GABA EC5 evoked currents at concentrations ranging from 0.01-1µM. Taken together these results reveal a mode of action of CBD on specifically configured GABAA receptors that may be relevant to the anticonvulsant and anxiolytic effects of the compound.

Chronic Methamphetamine Self-Administration Dysregulates Oxytocin Plasma Levels and Oxytocin Receptor Fibre Density in the Nucleus Accumbens Core and Subthalamic Nucleus of the Rat.

The neuropeptide oxytocin attenuates reward and abuse for the psychostimulant methamphetamine (METH). Recent findings have implicated the nucleus accumbens (NAc) core and subthalamic nucleus (STh) in oxytocin modulation of acute METH reward and relapse to METH-seeking behaviour. Surprisingly, the oxytocin receptor (OTR) is only modestly involved in both regions in oxytocin attenuation of METH-primed reinstatement. Coupled with the limited investigation of the role of the OTR in psychostimulant-induced behaviours, we primarily investigated whether there are cellular changes to the OTR in the NAc core and STh, as well as changes to oxytocin plasma levels, after chronic METH i.v. self-administration (IVSA) and after extinction of drug-taking. An additional aim was to examine whether changes to central corticotrophin-releasing factor (CRF) and plasma corticosterone levels were also apparent because of the interaction of oxytocin with stress-regulatory mechanisms. Male Sprague-Dawley rats were trained to lever press for i.v. METH (0.1 mg/kg/infusion) under a fixed-ratio 1 schedule or received yoked saline infusions during 2-h sessions for 20 days. An additional cohort of rats underwent behavioural extinction for 15 days after METH IVSA. Subsequent to the last day of IVSA or extinction, blood plasma was collected for enzyme immunoassay, and immunofluorescence was conducted on NAc core and STh coronal sections. Rats that self-administered METH had higher oxytocin plasma levels, and decreased OTR-immunoreactive (-IR) fibres in the NAc core than yoked controls. In animals that self-administered METH and underwent extinction, oxytocin plasma levels remained elevated, OTR-IR fibre density increased in the STh, and a trend towards normalisation of OTR-IR fibre density was evident in the NAc core. CRF-IR fibre density in both brain regions and corticosterone plasma levels did not change across treatment groups. These findings demonstrate that oxytocin systems, both centrally within the NAc core and STh, as well as peripherally through plasma measures, are dysregulated after METH abuse.

Cannabinoid replacement therapy (CRT): Nabiximols (Sativex) as a novel treatment for cannabis withdrawal.

Cannabis is a common recreational drug that is generally considered to have low addictive potential. However, an increasing number of cannabis users are seeking treatment for dependence on the drug. There is interest in using agonist (substitution) pharmacotherapies to treat cannabis dependence and here we outline a novel approach involving a buccal spray (nabiximols) that contains tetrahydrocannabinol (THC) and cannabidiol (CBD). We review recent research with nabiximols and highlight findings relevant to clinical practice.

Regional Fos-expression induced by γ-hydroxybutyrate (GHB): comparison with γ-butyrolactone (GBL) and effects of co-administration of the GABAB antagonist SCH 50911 and putative GHB antagonist NCS-382.

γ-Hydroxybutyrate (GHB) has a complex array of neural actions that include effects on its own high-affinity GHB receptor, the release of neuroactive steroids, and agonist actions at GABAA and GABAB receptors. We previously reported partial overlap in the c-Fos expression patterns produced by GHB and the GABAB agonist, baclofen in rats. The present study extends these earlier findings by examining the extent to which GHB Fos expression and behavioral sedation are prevented by (2S)-(+)-5,5-dimethyl-2-morpholineacetic acid (SCH 50911), a GABAB antagonist, and NCS-382, a putative antagonist at the high-affinity GHB receptor. We also compare Fos expression caused by GHB and its precursor γ-butyrolactone (GBL), which is a pro-drug for GHB but lacks the high sodium content of the parent GHB molecule. Both GHB (1,000 mg/kg) and GBL (600 mg/kg) induced rapid sedation in rats that lasted over 90 min and caused similar Fos expression patterns, albeit with GBL causing greater activation of the nucleus accumbens (core and shell) and dentate gyrus (granular layer). Pretreatment with SCH 50911 (100mg/kg) partly reversed the sedative effects of GHB and significantly reduced GHB-induced Fos expression in only four regions: the tenia tecta, lateral habenula, dorsal raphe and laterodorsal tegmental nucleus. NCS-382 (50mg/kg) had no effect on GHB-induced sedation or Fos expression. When given alone, both NCS-382 and SCH 50911 increased Fos expression in the bed nucleus of the stria terminalis, central amygdala, parasubthalamic nucleus and nucleus of the solitary tract. SCH 50911 alone affected the Islands of Calleja and the medial, central and paraventricular thalamic nuclei. Overall, this study shows a surprising lack of reversal of GHB-induced Fos expression by two relevant antagonists, both of which have marked intrinsic actions. This may reflect the limited doses tested but also suggests that GHB Fos expression reflects mechanisms independent of GHB and GABAB receptors.

Body temperature and cardiac changes induced by peripherally administered oxytocin, vasopressin and the non-peptide oxytocin receptor agonist WAY 267,464: a biotelemetry study in rats.

BACKGROUND AND PURPOSE: There is current interest in oxytocin (OT) as a possible therapeutic in psychiatric disorders. However, the usefulness of OT may be constrained by peripheral autonomic effects, which may involve an action at both OT and vasopressin V1A receptors. Here, we characterized the cardiovascular and thermoregulatory effects of OT, vasopressin (AVP) and the non-peptide OT receptor agonist WAY 267,464 in rats, and assessed the relative involvement of the OT and V1A receptors in these effects. EXPERIMENTAL APPROACH: Biotelemetry in freely moving male Wistar rats was used to examine body temperature and heart rate after OT (0.01 - 1 mg kg(-1); i.p.), AVP (0.001 - 0.1 mg kg(-1); i.p.) or WAY 267,464 (10 and 100 mg kg(-1); i.p.). The actions of the OT receptor antagonist Compound 25 (C25, 5 and 10 mg kg(-1)) and V1A receptor antagonist SR49059 (1 and 10 mg kg(-1)) were studied, as well as possible V1A receptor antagonist effects of WAY 267,464. KEY RESULTS: OT and AVP dose-dependently reduced body temperature and heart rate. WAY 267,464 had similar, but more modest, effects. SR49059, but not C25, prevented the hypothermia and bradycardia induced by OT and AVP. WAY 267,464 (100 mg·kg(-1)) prevented the effects of OT, and to some extent AVP. CONCLUSIONS AND IMPLICATIONS: Peripherally administered OT and AVP have profound cardiovascular and thermoregulatory effects that appear to principally involve the V1A receptor rather than the OT receptor. Additionally, WAY 267,464 is not a simple OT receptor agonist, as it has functionally relevant V1A antagonist actions.

Interleukin-18 deficiency and its long-term behavioural and cognitive impacts in a murine model of pneumococcal meningitis.

Pneumococcal meningitis often results in death or neurological sequelae, but the underlying pathogenetic mechanisms remain poorly understood. In C57BL/6J mice subjected to intracerebroventricular (icv) challenge with Streptococcus pneumoniae, the chemokine CCL2 and cytokines interferon-γ, interleukin (IL)-1ß, IL-6 and tumour necrosis factor were prominently expressed in the brain during the acute phase of the disease. The upregulation of these immune mediators was markedly diminished in IL-18-deficient mice. Uninfected IL-18(-/-) mice exhibited decreases in anxiety phenotype and licking behaviour, and an increase in behavioural habituation, in an automated monitoring system (the IntelliCage). Without antibiotic intervention, a majority of IL-18(+/+) mice developed irreversible disease after icv S. pneumoniae but this was significantly improved by deleting IL-18 gene function. IL-18(+/+) mice cured of pneumococcal meningitis with four doses of ceftriaxone, initiated at 20 h post-inoculation, showed enduring sequelae. These included abnormal behavioural phenotypes featuring diurnal hypoactivity and nocturnal hyperactivity, light phobia and disrupted cognitive function. While the hyperactive phenotype was absent in the corresponding IL-18(-/-) survivors, cognitive impairments and behavioural deficits were still present. Overall, the results suggest that the high levels of cytokines and/or chemokines released after pneumococcal challenge provoked a series of pathological events, ultimately causing acute death. Furthermore, since only a subset of behavioural phenotypes were ameliorated in the pneumococcus-infected IL-18(-/-) mice, the pathological pathways causing mortality may be, at least in part, distinct from those leading to long-term neurological sequelae.

A novel automated test battery reveals enduring behavioural alterations and cognitive impairments in survivors of murine pneumococcal meningitis.

Pneumococcal meningitis, caused by Streptococcus pneumoniae infection, is a major form of lethal bacterial meningitis. Survivors are predisposed to developing lifelong disabling sequelae, including cognitive impairment, psychological problems and motor deficits. In our experimental model, ventricular inoculation of 10(5) colony-forming units of S. pneumoniae type 3 caused 90% of mice to develop life-threatening meningitis within 48 h. Antibiotic treatment with ceftriaxone 20 h post infection reduced the incidence of severe meningitis to <10%. At the time of treatment, upregulation of pro-inflammatory cytokines was detected, including interleukin-1ß, interleukin-6 and tumour necrosis factor. We evaluated the long-term behavioural and cognitive sequelae in control mice and those surviving meningitis using an automated system (the IntelliCage) in which mice perform a range of behavioural and spatial tasks to obtain water rewards from conditioning units in their home cage. Surviving mice showed a number of altered behaviours relative to controls, including (i) hypoexploration when first exposed to the IntelliCage, (ii) altered activity patterns (fewer visits to conditioning stations during the light phase and more in the dark phase), (iii) avoidance of light (a constant or flashing LED stimulus), (iv) impaired spatial learning (a complex patrolling task), and (v) impaired discrimination reversal learning. Overall these results suggest photophobia and weakened learning ability in post-meningitic mice, particularly on tasks engaging hippocampal and prefrontal neural substrates. This study also demonstrates a standardised and comprehensive battery of tests that can be readily used to investigate neurological sequelae in undisturbed mice residing in a complex home cage environment.

The nonpeptide oxytocin receptor agonist WAY 267,464: receptor-binding profile, prosocial effects and distribution of c-Fos expression in adolescent rats.

Previous research suggests that the nonpeptide oxytocin receptor (OTR) agonist WAY 267,464 may only partly mimic the effects of oxytocin in rodents. The present study further explored these differences and related them to OTR and vasopressin 1a receptor (V(1a) R) pharmacology and regional patterns of c-Fos expression. Binding data for WAY 267,464 and oxytocin were obtained by displacement binding assays on cellular membranes, while functional receptor data were generated by luciferase reporter assays. For behavioural testing, adolescent rats were tested in a social preference paradigm, the elevated plus-maze (EPM) and for locomotor activity changes following WAY 267,464 (10 and 100 mg/kg, i.p.) or oxytocin (0.1 and 1 mg/kg, i.p.). The higher doses were also examined for their effects on regional c-Fos expression. Results showed that WAY 267,464 had higher affinity (K(i) ) at the V(1a) R than the OTR (113 versus 978 nm). However, it had no functional response at the V(1a) R and only a weak functional effect (EC(50) ) at the OTR (881 nm). This suggests WAY 267,464 is an OTR agonist with weak affinity and a possible V(1a) R antagonist. Oxytocin showed high binding at the OTR (1.0 nm) and V(1a) R (503 nm), with a functional EC(50) of 9.0 and 59.7 nm, respectively, indicating it is a potent OTR agonist and full V(1a) R agonist. WAY 267,464 (100 mg/kg), but not oxytocin, significantly increased the proportion of time spent with a live rat, over a dummy rat, in the social preference test. Neither compound affected EPM behaviour, whereas the higher doses of WAY 267,464 and oxytocin suppressed locomotor activity. WAY 267,464 and oxytocin produced similar c-Fos expression in the paraventricular hypothalamic nucleus, central amygdala, lateral parabrachial nucleus and nucleus of the solitary tract, suggesting a commonality of action at the OTR with the differential doses employed. However, WAY 267,464 caused greater c-Fos expression in the medial amygdala and the supraoptic nucleus than oxytocin, and lesser effects in the locus coeruleus. Overall, our results confirm the differential effects of WAY 267,464 and oxytocin and suggest that this may reflect contrasting actions of WAY 267,464 and oxytocin at the V(1a) R. Antagonism of the V(1a) R by WAY 267,464 could underlie some of the prosocial effects of this drug either through a direct action or through disinhibition of oxytocin circuitry that is subject to vasopressin inhibitory influences.

Regional c-Fos and FosB/ΔFosB expression associated with chronic methamphetamine self-administration and methamphetamine-seeking behavior in rats.

The regional expression of the transcription factors c-Fos and FosB/ΔFosB was examined in rats given acute exposure to intravenous methamphetamine (METH) or repeated intravenous METH self-administration. One group of rats self-administered METH via lever pressing in 2 h sessions every day for 3 weeks and on a final test day received self-administered METH as usual. A second group with the same METH self-administration history received saline infusions on the test day, to induce drug-seeking behavior. Other rats were trained with infusions of intravenous saline that were yoked to the passive delivery of METH in the other two groups. On test day, half of these yoked rats received passive METH infusions for the first time, whereas the others received saline as usual. The results showed that acute METH produced a characteristic signature of Fos expression with elevations in striatal, cortical, and extended amygdala regions. Importantly, rats with a 3-week history of METH self-administration displayed similar regional Fos expression to rats receiving METH for the first time. Rats seeking, but not receiving, METH on the test day had augmented Fos in the lateral hypothalamus, septum, and vertical limb of the diagonal band of Broca, suggesting a primary role for these regions in METH-seeking behavior. Both acute and chronic METH activated orexin-positive cells in the perifornical area of the hypothalamus. FosB/ΔFosB was elevated in the lateral hypothalamus, posterior ventral tegmental area, central amygdala, and dorsal raphe of all the rats with a history of METH self-administration. This occurred regardless of whether they received METH on test day, suggesting presence of the long-lived FosB isoform, ΔFosB. Overall, these results show persistent upregulated regional brain Fos and FosB/ΔFosB expression with chronic METH self-administration and indicate a role for the lateral hypothalamus and lateral septum in METH-seeking behavior.

The major plant-derived cannabinoid Δ(9)-tetrahydrocannabinol promotes hypertrophy and macrophage infiltration in adipose tissue.

Synthetic cannabinoid receptor agonists activate lipoprotein lipase and the formation of lipid droplets in cultured adipocytes. Here we extend this work by examining whether Δ(9)-tetrahydrocannabinol (THC), a major plant-derived cannabinoid, increases adipocyte size in vivo. Further, possibly as a consequence of hypertrophy, we hypothesize that THC exposure promotes macrophage infiltration into adipose tissue, an inflammatory state observed in obese individuals. Rats repeatedly exposed to THC in vivo had reduced body weight, fat pad weight, and ingested less food over the drug injection period. However, THC promoted adipocyte hypertrophy that was accompanied by a significant increase in cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) expression, an enzyme important in packaging triglycerides. We also showed that THC induced macrophage infiltration and increased expression of the inflammatory cytokine tumor necrosis factor alpha (TNF-α) in adipose tissue but did not induce apoptosis as measured by TUNEL staining. That THC increased adipocyte cell size in the absence of greater food intake, body weight and fat provides a unique model to explore mechanisms underlying changes in adipocyte size associated with a mild inflammatory state in fat tissue.

Resilience and reduced c-Fos expression in P2X7 receptor knockout mice exposed to repeated forced swim test.

There is considerable evidence suggesting genetic factors play an important role in the pathophysiology of depression, possibly by increasing susceptibility to repeated environmental stressors. Recent linkage studies have associated a polymorphism of the gene coding for the P2X7 receptor (P2X7R) with both major depressive disorder and bipolar disorder. Here we assessed whether P2X7 deletion affected the behavioural and neural response to repeated stress. P2X7R knockout (P2X7-/-) mice were subjected to the forced swim test for three consecutive days and neuronal activation in response to the third exposure was assessed using c-Fos immunohistochemistry. In addition, anxiety was evaluated in another group of P2X7-/- mice using the elevated plus maze (EPM) and light dark emergence (LDE) tests. Equivalent levels of immobility were observed in P2X7-/- mice and wild-type (WT) mice on the first exposure to forced swim, but much greater immobility was seen in WT mice on second and third exposures. This suggests that P2X7-/- mice exhibit an impaired adaptive coping response to repeated stress. Reinforcing this view, c-Fos expression in the dentate gyrus of the hippocampus and in the basolateral amygdala was seen in WT mice but not P2X7-/- mice following repeated forced swim. In addition, decreased locomotor activity was detected in P2X7-/- mice without any specific effects on anxiety in the LDE test. However, P2X7-/- mice showed greater anxiety-like behaviour in the EPM. These data suggest that the P2X7R may be involved in the adaptive mechanisms elicited by exposure to repeated environmental stressors that leads to the development of depression-like behaviours. This suggests that P2X7R antagonists may be useful therapeutics for the treatment of major depression, possibly by increasing resilience in the face of repeated stress.

Weekly gamma-hydroxybutyrate exposure sensitizes locomotor hyperactivity to low-dose 3,4-methylenedioxymethamphetamine in rats.

Users of the popular party drug 3,4-methylenedioxymethamphetamine (MDMA) sometimes report combining MDMA with gamma-hydroxybutyrate (GHB) to enhance the pleasurable effects of both drugs. However, very few studies have examined the influences of this drug combination. The present study investigated the development of locomotor sensitization in laboratory rats given 7 once-weekly exposures to either MDMA, GHB or their combination (MDMA/GHB). The drugs were administered at a high ambient temperature (28 degrees C) to mimic nightclub conditions. MDMA (5 mg/kg), given once weekly, produced a progressively greater locomotor and hyperthermic response over time. In contrast, GHB (500 mg/kg) administered weekly produced consistent low levels of locomotor activity and few changes in body temperature. Rats receiving the mixture of MDMA (5 mg/kg) and GHB (500 mg/kg) showed asymptotic levels of sensitized locomotor activity similar to those seen in rats given MDMA alone, but the development of locomotor sensitization was delayed by coadministered GHB. GHB also delayed the development of MDMA-induced hyperthermia. After a washout period of 5 weeks, rats pre-exposed to MDMA, GHB and MDMA/GHB showed no hyperactivity when tested drug-free in the context in which they had previously received drugs, but displayed a sensitized locomotor response to a low challenge dose of MDMA (2.5 mg/kg). The response to a low dose of methamphetamine (0.5 mg/kg) did not differ among groups. Neurochemical analysis using high-performance liquid chromatography revealed few lasting changes in serotonin, dopamine or their metabolites in the striatum or prefrontal cortex of MDMA- or GHB-pre-exposed rats. These results indicate that GHB modulates the locomotor and hyperthermic response to acute MDMA and that pre-exposure to GHB can sensitize the locomotor response to low doses of MDMA.

Reintoxication: the release of fat-stored delta(9)-tetrahydrocannabinol (THC) into blood is enhanced by food deprivation or ACTH exposure.

BACKGROUND AND PURPOSE: Delta(9)-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, accumulates in adipose tissue where it is stored for long periods of time. Here we investigated whether conditions that promote lipolysis can liberate THC from adipocytes to yield increased blood levels of THC. EXPERIMENTAL APPROACH: In vitro studies involved freshly isolated rat adipocytes that were incubated with THC before exposure to the lipolytic agent adrenocorticotrophic hormone (ACTH). A complementary in vivo approach examined the effects of both food deprivation and ACTH on blood levels of THC in rats that had been repeatedly injected with THC (10 mg.kg(-1)) for 10 consecutive days. Lipolysis promoted by ACTH or food deprivation was indexed by measurement of glycerol levels. KEY RESULTS: ACTH increased THC levels in the medium of THC-pretreated adipocytes in vitro. ACTH also enhanced THC release from adipocytes in vitro when taken from rats repeatedly pretreated with THC in vivo. Finally, in vivo ACTH exposure and 24 h food deprivation both enhanced the levels of THC and its metabolite, (-)-11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (THC-COOH) in the blood of rats that had been pre-exposed to repeated THC injections. CONCLUSIONS AND IMPLICATIONS: The present study shows that lipolysis enhances the release of THC from fat stores back into blood. This suggests the likelihood of 'reintoxication' whereby food deprivation or stress may raise blood THC levels in animals chronically exposed to the drug. Further research will need to confirm whether this can lead to functional effects, such as impaired cognitive function or 'flashbacks'.

The distribution of gamma-hydroxybutyrate-induced Fos expression in rat brain: comparison with baclofen.

gamma-Hydroxybutyrate (GHB) is a euphoric, prosocial and sleep inducing drug that binds with high affinity to its own GHB receptor site and also more weakly to GABA(B) receptors. GHB is efficacious in the treatment of narcolepsy and alcoholism, but heavy use can lead to dependence and withdrawal. Many effects of GHB (sedation, hypothermia, catalepsy) are mimicked by GABA(B) receptor agonists (e.g. baclofen). However other effects (euphoric and prosocial effects and a therapeutic effect in narcolepsy) are not. The present study used Fos immunohistochemistry to assess the neural activation produced in rat brain by medium to high doses of GHB (250, 500 and 1000 mg/kg) and a high dose of baclofen (10 mg/kg) that produced similar sedation to 500 mg/kg GHB. Results showed many common regions of activation with these two drugs including the supraoptic, paraventricular, median preoptic and ventral premammillary nuclei of the hypothalamus, the central nucleus of the amygdala, Edinger-Westphal nucleus, lateral parabrachial nucleus, locus coeruleus, and nucleus of the solitary tract. GHB (500 mg/kg), but not baclofen (10 mg/kg), induced significant Fos expression in the median raphe nucleus and lateral habenula, while a higher dose of GHB (1000 mg/kg) induced additional Fos expression in the islands of Calleja, dentate gyrus (polymorphic layer) and arcuate nucleus, and in various regions implicated in rapid and non-rapid eye movement sleep (laterodorsal tegmental nucleus, tuberomammillary nucleus and the ventrolateral and anterodorsal preoptic nuclei). Surprisingly, Fos immunoreactivity was not observed with either GHB or baclofen in reward-relevant regions such as the nucleus accumbens, striatum and ventral tegmental area. Overall these results indicate a distinctive signature of brain activation with GHB that may be only partly due to GABA(B) receptor effects. This confirms a unique neuropharmacological profile for GHB and indicates key neural substrates that may underlie its characteristic influence on sleep, body temperature, sociability and endocrine function.

Neural correlates of MDMA ("Ecstasy")-induced social interaction in rats.

The popular drug 3,4 methylenedioxymethamphetamine (MDMA, "Ecstasy", "the Love Drug") produces feelings of love and closeness in humans and induces analogous prosocial and antiaggressive effects in laboratory animals. Here we examined the specific brain regions that may be involved in these prosocial effects. Male Wistar rats were pretreated with a moderate dose of MDMA (5 mg/kg) or vehicle and then either kept alone in a familiar test chamber for 60 min (groups MDMA-ALONE and VEHICLE-ALONE) or allowed to engage in social interaction in the familiar test chamber with an unfamiliar same-sex conspecific for 60 min (groups MDMA-SOCIAL and VEHICLE-SOCIAL). Rats in the MDMA-SOCIAL group showed much greater overall social interaction than rats in the VEHICLE-SOCIAL group, with microanalysis revealing increased general investigation of other rats but decreased anogenital sniffing. Analysis of neural activation across 39 brain regions using Fos immunohistochemistry showed the following results: (1) VEHICLE-SOCIAL and VEHICLE-ALONE groups did not differ in Fos expression, indicating that a social context per se did not affect Fos expression, (2) MDMA-treated groups showed significantly increased Fos expression relative to VEHICLE treated groups in 30 brain regions, (3) the MDMA-SOCIAL group showed augmented Fos expression relative to the MDMA-ALONE group in six brain regions including the caudate-putamen (medial), medial preoptic area, paraventricular thalamic nucleus, central amygdala, ventromedial hypothalamic nucleus, and the medial amygdala (posterodorsal), and (4) the MDMA-SOCIAL group (but not the MDMA-ALONE group) showed augmented Fos expression relative to the VEHICLE groups in the nucleus accumbens, ventral tegmental area and periaqueductal grey. These results indicate that a moderate dose of MDMA given in a social context causes considerably greater brain activation than the same dose given to solitary rats. This activation involves specific neural circuits that are known to regulate affiliative behavior, perhaps by modulating the incentive value of social stimuli. A possible role for the neuropeptide oxytocin in mediating the prosocial effects of MDMA is discussed.

From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long-term adverse consequences of drug use?

Addictive drugs can profoundly affect social behaviour both acutely and in the long-term. Effects range from the artificial sociability imbued by various intoxicating agents to the depressed and socially withdrawn state frequently observed in chronic drug users. Understanding such effects is of great potential significance in addiction neurobiology. In this review we focus on the 'social neuropeptide' oxytocin and its possible role in acute and long-term effects of commonly used drugs. Oxytocin regulates social affiliation and social recognition in many species and modulates anxiety, mood and aggression. Recent evidence suggests that popular party drugs such as MDMA and gamma-hydroxybutyrate (GHB) may preferentially activate brain oxytocin systems to produce their characteristic prosocial and prosexual effects. Oxytocin interacts with the mesolimbic dopamine system to facilitate sexual and social behaviour, and this oxytocin-dopamine interaction may also influence the acquisition and expression of drug-seeking behaviour. An increasing body of evidence from animal models suggests that even brief exposure to drugs such as MDMA, cannabinoids, methamphetamine and phencyclidine can cause long lasting deficits in social behaviour. We discuss preliminary evidence that these adverse effects may reflect long-term neuroadaptations in brain oxytocin systems. Laboratory studies and preliminary clinical studies also indicate that raising brain oxytocin levels may ameliorate acute drug withdrawal symptoms. It is concluded that oxytocin may play an important, yet largely unexplored, role in drug addiction. Greater understanding of this role may ultimately lead to novel therapeutics for addiction that can improve mood and facilitate the recovery of persons with drug use disorders.

Automated scoring of novel object recognition in rats.

The object recognition task (ORT) has become increasingly popular as a memory test in neuroscience research. Scoring of ORT performance is still mostly done by hand, which can be liable to subjective scoring. To our knowledge, no suited software is available yet since the direction of the nose of the animal cannot be tracked reliably. We have developed a software paradigm that reliably tracks the nose of the rats and have conducted a series of experiments to evaluate the reliability of this newly developed program. We used Wistar rats, which showed good object memory after 1h interval. Subsequently, we used scopolamine (SCOP) to impair the memory performance of the rats. The object exploration was scored by two observers and the automated system. Both observers and the automated system found an impairing drug effect of scopolamine on ORT performance. When using large objects the correlation between the discrimination index d2 of observers was: 0.60 (SCOP) and 0.79 (SAL). However, the correlation between observers and the automated system was quite low: 0.41 (SCOP) and 0.40 (SAL). Reducing the size of the objects increased the reliability between observers and the automated system substantially (0.82-0.87). We conclude that the use of small objects in combination with our program enables reliable automated scoring in the ORT, thus increasing the objectivity and validity of this task.