Effects of the synthetic cannabinoid nabilone on spatial learning and hippocampal neurotransmission

In Vivo Bio-Activation of JWH-175 to JWH-018: Pharmacodynamic and Pharmacokinetic Studies in Mice

3-(1-Naphthalenylmethyl)-1-pentyl-1H-indole (JWH-175) is a synthetic cannabinoid illegally marketed for its psychoactive cannabis-like effects. This study aimed to investigate and compare in vitro and in vivo pharmacodynamic activity of JWH-175 with that of 1-naphthalenyl (1-pentyl-1H-indol-3-yl)-methanone (JWH-018), as well as evaluate the in vitro (human liver microsomes) and in vivo (urine and plasma of CD-1 male mice) metabolic profile of JWH-175. In vitro binding studies showed that JWH-175 is a cannabinoid receptor agonist less potent than JWH-018 on mouse and human CB1 and CB2 receptors. In agreement with in vitro data, JWH-175 reduced the fESPS in brain hippocampal slices of mice less effectively than JWH-018. Similarly, in vivo behavioral studies showed that JWH-175 impaired sensorimotor responses, reduced breath rate and motor activity, and increased pain threshold to mechanical stimuli less potently than JWH-018. Metabolic studies demonstrated that JWH-175 is rapidly bioactivated to JWH-018 in mice blood, suggesting that in vivo effects of JWH-175 are also due to JWH-018 formation. The pharmaco-toxicological profile of JWH-175 was characterized for the first time, proving its in vivo bio-activation to the more potent agonist JWH-018. Thus, it highlighted the great importance of investigating the in vivo metabolism of synthetic cannabinoids for both clinical toxicology and forensic purposes.

Cannabinoid and endocannabinoid system: a promising therapeutic intervention for multiple sclerosis

Multiple sclerosis (MS) is a chronic and complex neurodegenerative disease, distinguished by the presence of lesions in the central nervous system (CNS) due to exacerbated immunological responses that inflict oligodendrocytes and the myelin sheath of axons. In recent years, studies have focused on targeted therapeutics for MS that emphasize the role of G protein-coupled receptors (GPCRs), specifically cannabinoids receptors. Clinical studies have suggested the therapeutic potential of cannabinoids derived from Cannabis sativa in relieving pain, tremors and spasticity. Cannabinoids also appear to prevent exaggerated immune responses in CNS due to compromised blood-brain barrier. Both, endocannabinoid system (ECS) modulators and cannabinoid ligands actively promote oligodendrocyte survival by regulating signaling, migration and myelination of nerve cells. The cannabinoid receptors 1 (CB1) and 2 (CB2) of ECS are the main ones in focus for therapeutic intervention of MS. Various CB1/CB2 receptors agonists have been experimentally studied which showed anti-inflammatory properties and are considered to be effective as potential therapeutics for MS. In this review, we focused on the exacerbated immune attack on nerve cells and the role of the cannabinoids and its interaction with the ECS in CNS during MS pathology.

Synthetic cannabinoid JWH-018 and its halogenated derivatives JWH-018-Cl and JWH-018-Br impair Novel Object Recognition in mice: Behavioral, electrophysiological and neurochemical evidence

It is well known that an impairment of learning and memory function is one of the major physiological effects caused by natural or synthetic cannabinoid consumption in rodents, nonhuman primates and in humans. JWH-018 and its halogenated derivatives (JWH-018-Cl and JWH-018-Br) are synthetic CB1/CB2 cannabinoid agonists, illegally marketed as "Spice" and "herbal blend" for their Cannabis-like psychoactive effects. In the present study the effects of acute exposure to JWH-018, JWH-018-Cl, JWH-018-Br (JWH-018-R compounds) and Δ(9)-THC (for comparison) on Novel Object Recognition test (NOR) has been investigated in mice. Moreover, to better characterize the effects of JWH-018-R compounds on memory function, in vitro electrophysiological and neurochemical studies in hippocampal preparations have been performed. JWH-018, JWH-018-Cl and JWH-018-Br dose-dependently impaired both short- and long-memory retention in mice (respectively 2 and 24 h after training session). Their effects resulted more potent respect to that evoked by Δ(9)-THC. Moreover, in vitro studies showed as JWH-018-R compounds negatively affected electrically evoked synaptic transmission, LTP and aminoacid (glutamate and GABA) release in hippocampal slices. Behavioral, electrophysiological and neurochemical effects were fully prevented by CB1 receptor antagonist AM251 pretreatment, suggesting a CB1 receptor involvement. These data support the hypothesis that synthetic JWH-018-R compounds, as Δ(9)-THC, impair cognitive function in mice by interfering with hippocampal synaptic transmission and memory mechanisms. This data outline the danger that the use and/or abuse of these synthetic cannabinoids may represent for the cognitive process in human consumer.

Effects of co-administration of 2-arachidonylglycerol (2-AG) and a selective µ-opioid receptor agonist into the nucleus accumbens on high-fat feeding behaviors in the rat

Previous research has demonstrated that the nucleus accumbens is a site where opioids and cannabinoids interact to alter feeding behavior. However, the influence of the endocannabinoid 2-arachidonylglycerol (2-AG) on the well-characterized model of intra-accumbens opioid driven high-fat feeding behavior has not been explored. The present experiments examined high-fat feeding associated behaviors produced by the interaction of 2-AG and the μ-opioid receptor agonist DAla(2),N,Me-Phe(4),Gly-ol(5)-enkaphalin (DAMGO) administered into the nucleus accumbens. Sprague-Dawley rats were implanted with bilateral cannulae aimed at the nucleus accumbens and were co-administered both a sub-threshold dose of 2-AG (0 or 0.25 μg/0.5 μl/side) and DAMGO (0, 0.025 μg or 0.25 μg/0.5 μl/side) in all dose combinations, and in a counterbalanced order. Animals were then immediately allowed a 2h-unrestricted access period to a palatable high-fat diet. Consumption, number and duration of food hopper entries, and locomotor activity were all monitored. DAMGO treatment led to an increase in multiple behaviors, including consumption, duration of food hopper entry, and locomotor activity. However, combined intra-accumbens administration of DAMGO and a subthreshold dose of 2-AG led to a significant increase in number of food hopper entries and locomotor activity, compared to DAMGO by itself. The results confirm that intra-accumbens administration of subthreshold dose of the endogenous cannabinoid 2-AG increases the DAMGO-induced approach and locomotor behaviors associated with high-fat feeding.

Effects of endocannabinoid system modulation on cognitive and emotional behavior

Cannabis has long been known to produce cognitive and emotional effects. Research has shown that cannabinoid drugs produce these effects by driving the brain’s endogenous cannabinoid system and that this system plays a modulatory role in many cognitive and emotional processes. This review focuses on the effects of endocannabinoid system modulation in animal models of cognition (learning and memory) and emotion (anxiety and depression). We review studies in which natural or synthetic cannabinoid agonists were administered to directly stimulate cannabinoid receptors or, conversely, where cannabinoid antagonists were administered to inhibit the activity of cannabinoid receptors. In addition, studies are reviewed that involved genetic disruption of cannabinoid receptors or genetic or pharmacological manipulation of the endocannabinoid-degrading enzyme, fatty acid amide hydrolase (FAAH). Endocannabinoids affect the function of many neurotransmitter systems, some of which play opposing roles. The diversity of cannabinoid roles and the complexity of task-dependent activation of neuronal circuits may lead to the effects of endocannabinoid system modulation being strongly dependent on environmental conditions. Recent findings are reviewed that raise the possibility that endocannabinoid signaling may change the impact of environmental influences on emotional and cognitive behavior rather than selectively affecting any specific behavior.

Nabilone produces marked impairments to cognitive function and changes in subjective state in healthy volunteers

This was a double-blind, randomised, placebo-controlled, crossover study of the acute cognitive and subjective effects of nabilone 1-3 mg in healthy male volunteers. The Cognitive Drug Research computerised system (CDR system) was used to assess changes in attention, working and episodic memory. In addition, a number of self-ratings were conducted including those of mood, alertness and perceived drug effects. Impairments to attention, working and episodic memory and self-ratings of alertness were evident. Volunteers also experienced a number of subjective drug effects. These data demonstrate that acute doses of nabilone in the range 1-3 mg produce clear cognitive and subjective effects in healthy volunteers, and therefore they may be used as reference data in the future study of peripherally acting cannabinoids believed to be free from such effects.

Localization of CB1 cannabinoid receptor mRNA in the brain of the chick (Gallus domesticus)

The cannabinoid receptor one (CB1) is prevalent in the brains of many species. Receptor binding, in situ hybridization and immunohistochemical surveys have described the distribution of this receptor in a limited number of species. The current study used in situ hybridization to examine the expression of CB1 mRNA in the chick brain, a non-mammalian vertebrate. The results were compared to the observed patterns of expression for CB1 mRNA, protein, and agonist binding that have been reported for other avian species and mammals. Importantly, since CB1 receptors are typically located on neuronal terminals, comparison of the somatic mRNA expression with previously reported descriptions of the location of functional receptors, allows speculation about the circuits that make use of these receptors. The expression pattern for CB1 mRNA appears to be highly conserved across species in key areas such as the cerebellum and portions of the forebrain. For example, high levels of expression were observed in the avian amygdala and hippocampus, areas which express high levels of CB1 in mammals. The avian substantia nigra and ventral tegmental area, however, showed specific labeling. This finding is in stark contrast to the high levels of receptor binding or CB1 protein, but not CB1 mRNA in these areas of the mammalian brain. Moderate labeling was also seen throughout the hyperpallium and mesopallium. Throughout the brain, a number of regions that are known to be involved in visual processing displayed high levels of expression. For example, the tectum also had strong mRNA expression within layers 9-11 of the stratum griseum et fibrosum superficale and stratum album centrale.

Low dose treatment with the synthetic cannabinoid Nabilone significantly reduces spasticity-related pain

About 30% of patients with chronic upper motor neuron syndrome (UMNS) suffer from disabling spasticity-related pain not sufficiently correctable by conventional treatment. Delta9-tetrahydrocannabinol (Delta(9)-THC) was reported to add benefit in the treatment of pain in patients with multiple sclerosis (MS). The question arose whether synthetic cannabinoids with lower potential for psychotropic side effects could be effective as well. To evaluate the safety and efficacy of low dose treatment with the synthetic cannabinoid Nabilone (1 mg per day) on spasticity-related pain a placebo-controlled double-blind crossover trial was performed.11 out of 13 included patients completed the study. The 11-Point-Box-Test showed a significant decrease of pain under Nabilone (p < 0.05), while spasticity, motor function and activities of daily living did not change. 5 patients reported side effects: one moderate transient weakness of the lower limbs (Nabilone phase, drop out), three mild drowsiness (two Nabilone, one placebo) and one mild dysphagia (placebo). One patient was excluded from the study due to an acute relapse of multiple sclerosis (Nabilone phase, drop out). Nabilone 1 mg per day proved to be a safe and easily applicable option in the care of patients with chronic UMNS and spasticity-related pain otherwise not controllable.

Endocannabinoids potently protect the newborn brain against AMPA-kainate receptor-mediated excitotoxic damage

Brain lesions induced in newborn mice or rats by the glutamatergic agonists ibotenate (acting on NMDA and metabotropic receptors) or S-bromowillardiine (acting on AMPA-kainate receptors) mimic some aspects of white matter cysts and transcortical necrosis observed in human perinatal brain damage associated with cerebral palsy. Exogenous and endogenous cannabinoids have received increasing attention as potential neuroprotective agents in a number of neurodegenerative disorders of the adult. One recent study showed neuroprotection by the cannabinoid agonist WIN-55212 in a newborn rat model of acute severe asphyxia. The present study was designed to assess the neuroprotective effects of the endogenous cannabinoid anandamide using a well-defined rodent model of neonatal excitotoxic brain lesions. In this model, anandamide provided dose-dependent and long-lasting protection of developing white matter and cortical plate reducing the size of lesions induced by S-bromowillardiine. Anandamide had only marginal neuroprotective effect against ibotenate-induced cortical grey matter lesions. Anandamide-induced neuroprotection against AMPA-kainate receptor-mediated brain lesions were blocked by a CB1 antagonist but not by a CB2 antagonist. Furthermore, anandamide effects were mimicked by a CB1 agonist but not by a CB2 agonist. Real-time PCR confirmed the expression of CB1 receptors, but not CB2 receptors, in the untreated newborn neocortex. Finally, neuroprotective effects of anandamide in white matter involved increased survival of preoligodendrocytes and better preservation of myelination. The present study provides experimental support for the role of endocannabinoids as a candidate therapy for excitotoxic perinatal brain lesions.

The effect of nabilone on neuropsychological functions related to driving ability: an extended case series

The primary goal of this prospective extended case series was to obtain the first data about the potential influence of nabilone intake on driving ability related neuropsychological functions. Six patients were investigated within a placebo controlled, double-blind crossover study of this synthetic cannabinoid (2 mg/day) in patients with multiple sclerosis and spasticity associated pain. Five neuropsychological functions (reaction time, working memory, divided attention, psychomotor speed and mental flexibility) were assessed. No indication was found of a deterioration of any of the five investigated neuropsychological functions during the 4-week treatment period with nabilone.

Cannabinoid function in learning, memory and plasticity

Marijuana and its psychoactive constituents induce a multitude of effects on brain function. These include deficits in memory formation, but care needs to be exercised since many human studies are flawed by multiple drug abuse, small sample sizes, sample selection and sensitivity of psychological tests for subtle differences. The most robust finding with respect to memory is a deficit in working and short-term memory. This requires intact hippocampus and prefrontal cortex, two brain regions richly expressing CB1 receptors. Animal studies, which enable a more controlled drug regime and more constant behavioural testing, have confirmed human results and suggest, with respect to hippocampus, that exogenous cannabinoid treatment selectively affects encoding processes. This may be different in other brain areas, for instance the amygdala, where a predominant involvement in memory consolidation and forgetting has been firmly established. While cannabinoid receptor agonists impair memory formation, antagonists reverse these deficits or act as memory enhancers. These results are in good agreement with data obtained from electrophysiological recordings, which reveal reduction in neural plasticity following cannabinoid treatment, and increased plasticity following antagonist exposure. The mixed receptor properties of the pharmacological tool, however, make it difficult to define the exact role of any CB1 receptor population in memory processes with any certainty. This makes it all the more important that behavioural studies use selective administration of drugs to specific brain areas, rather than global administration to whole animals. The emerging role of the endogenous cannabinoid system in the hippocampus may be to facilitate the induction of long-term potentiation/the encoding of information. Administration of exogenous selective CB1 agonists may therefore disrupt hippocampus-dependent learning and memory by 'increasing the noise', rather than 'decreasing the signal' at potentiated inputs.