Potent Cannabinoid Agonist Research Articles

WIN55,212-2 Attenuates Cognitive Impairments in AlCl3 + d-Galactose-Induced Alzheimer's Disease Rats by Enhancing Neurogenesis and Reversing Oxidative Stress.

Neurotransmission and cognitive dysfunctions have been linked to old age disorders including Alzheimer’s disease (AD). Aluminium is a known neurotoxic metal, whereas d-galactose (d-gal) has been established as a senescence agent. WIN55,212-2 (WIN), is a potent cannabinoid agonist which partially restores neurogenesis in aged rats. The current study aimed to explore the therapeutic potentials of WIN on Aluminium chloride (AlCl3) and d-gal-induced rat models with cognitive dysfunction. Healthy male albino Wistar rats weighing between 200–250 g were injected with d-gal 60 mg/kg intra peritoneally (i.p), while AlCl3 (200 mg/kg) was orally administered once daily for 10 consecutive weeks. Subsequently, from weeks 8–11 rats were co-administered with WIN (0.5, 1 and 2 mg/kg/day) and donepezil 1 mg/kg. The cognitive functions of the rats were assessed with a Morris water maze (MWM). Furthermore, oxidative stress biomarkers; malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) and neurogenesis markers: Nestin and glial fibrillary acidic protein (GFAP) were also evaluated, as well as the histology of the hippocampus. The results revealed that rats exposed to AlCl3 and d-gal alone showed cognitive impairments and marked neuronal loss (p < 0.05) in their hippocampal conus ammonis 1 (CA1). Additionally, a significant decrease in the expressions of GFAP and Nestin was also observed, including increased levels of MDA and decreased levels of SOD and GSH. However, administration of WIN irrespective of the doses given reversed the cognitive impairments and the associated biochemical derangements. As there were increases in the levels SOD, GSH, Nestin and GFAP (p < 0.05), while a significant decrease in the levels of MDA was observed, besides attenuation of the aberrant cytoarchitecture of the rat’s hippocampi. The biochemical profiles of the WIN-treated rats were normal. Thus, these findings offer possible scientific evidence of WIN being an effective candidate in the treatment of AD-related cognitive deficits.

Acute Pharmacological Effects and Oral Fluid Concentrations of the Synthetic Cannabinoids JWH-122 and JWH-210 in Humans After Self-Administration: An Observational Study.

Synthetic cannabinoids (SCs) are a group of new psychoactive drugs used recreationally with potential health risks. They are monitored by the EU Early Warning System since 2010 due to severe adverse effects on consumers. JWH-122 and JWH-210 are naphthoylindole SCs and potent cannabinoid receptor CB1 and CB2 agonists. Information about the effects of SCs usually is available from intoxication cases and surveys, and few studies on humans after controlled administration or observational/naturalistic studies using standardized measures of cardiovascular and subjective effects are available. The aim of this study was to evaluate the acute pharmacological effects of JWH-122 and JWH-210 recreational consumption in a 4 h observational study and assess their disposition in oral fluid (OF). Sixteen volunteers self-administered 1 mg dose of JWH-122 (n = 8) or 2.25 mg mean dose of JWH-210 (range 2–3 mg, n = 8) by inhalation (smoking). Physiological parameters including blood pressure (systolic and diastolic), heart rate (HR), and cutaneous temperature were measured. A set of visual analog scales, the 49-item short-form version of the Addiction Research Center Inventory (ARCI), and the Evaluation of the Subjective Effects of Substances with Abuse Potential (VESSPA-SSE) were used for the evaluation of subjective effects. OF was collected at baseline and at 10, 20, and 40 min and 1, 2, 3, and 4 h after self-administration. Statistically significant increases in systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR were observed after JWH-122 self-administration but not after JWH-210 self-administration. JWH-210 self-administration produced significant changes in subjective drug effects, similar to those induced by THC (intensity, high, good effects, and hunger). The subjective effects following JWH-122 consumption were minimal. The maximal effects were mostly observed 20 min after intake. JWH-122 and JWH 210 OF concentration reached a peak 20 min after administration and could not be detected after 3 h. The results demonstrated a different pattern of effects of these two SCs. Due to the limitations of our observational study, further research with a larger sample and controlled studies are needed to better define the acute pharmacological effect and health risk profile of JWH-122 and JWH-210.

Chronic Exposure to WIN55,212-2 During Adolescence Alters Prefrontal Dopamine Turnover and Induces Sensorimotor Deficits in Adult Rats.

Several lines of evidence suggest that chronic exposure to cannabinoids during adolescence may increase the risk of schizophrenia. Studies of the disorder have identified altered cortical dopaminergic neurotransmission. In this study, we hypothesised that heightened endocannabinoid system activation via chronic exposure to a highly potent cannabinoid receptors agonist in adolescent rats would cause long-lasting neurobiological changes that may dramatically alter expression and functions of dopamine metabolising enzymes, comethyl-o-transferase (COMT) and monoamine oxidases MAO-A and MAO-B. To test this hypothesis, adult male rats (70 PND) undergoing chronic treatment of the highly potent and non-selective CB agonist WIN55,212-2 (1.2mg/kg) during adolescence (PND 30-50) were subjected after 20days washout period to prepulse inhibition of acoustic startle test (PPI) to confirm cannabinoid-induced sensorimotor-gating impairments and afterwards examined for COMT, MAO-A and MAO-B expression and activity in the prefrontal cortex. Chronic WIN55,212-2 exposure during adolescence caused disruption of PPI, increased cortical dopamine level, decreased COMT mRNA expression and decreased MAO-A and MAO-B enzymatic activities. These results indicate that chronic exposure to cannabinoids during adolescence induces sensorimotor-gating alterations which likely result from changes in the prefrontal cortex dopaminergic signalling. This has important implications for developing methods of targeting dopamine metabolising enzymes and/or sequelae of its dysregulation in cannabinoid-induced schizoaffective-like behaviour.

Revealing the Mechanism of Agonist-Mediated Cannabinoid Receptor 1 (CB1) Activation and Phospholipid-Mediated Allosteric Modulation.

Cannabinoid receptor 1 (CB1) mediates the functional responses of Δ9-tetrahydrocannabinol. Although progress has been made in understanding cannabinoid binding and receptor activation, detailed knowledge of the dynamics involved in the activation mechanism of CB1 is lacking. Here, we use recently determined CB1 crystal structures to analyze its transition from inactive to active state by performing unbiased microsecond-length molecular dynamics (MD) simulations, totaling 32 μs, with and without bound potent cannabinoid agonist CP-55940. CB1 activation is characterized by an upward axial movement of transmembrane (TM) helix 3, inward movement of TM7, and outward movement of TM6. These conformational changes collectively allow Gi protein docking, although fully active states of the receptor occur only transiently during MD simulations. Additionally, positive allosteric modulation of CB1 by anionic phospholipids is found to increase action of the bound agonist. Specifically, this involves protein-lipid interactions at intracellular loop 3, TM6, and ionic lock residue Arg2143.50.

Pharmacological Characterization of Synthetic Cannabinoid MAM‐2201: Radioligand Binding and Abuse‐Related Effects

Abuse of novel psychoactive substances (NPS) is growing at an alarming rate worldwide, and over 30% of all NPS identified by the UN Office on Drugs and Crime in 2016 were synthetic cannabinoids. The recent emergence of MAM‐2201 on the illicit market is troubling because this drug has no precedent in either the scientific or patent literature, and thus appears to be a novel compound developed specifically as a “gray market” drug of abuse. Structurally, MAM‐2201 is a hybrid of two known synthetic cannabinoid compounds (JWH‐122 and AM‐2201) and therefore presumably acts as a high‐efficacy agonist at cannabinoid receptors, but its pharmacological properties are unknown. Thus, the present studies characterized its cannabinoid‐like activities in vitro and in vivo. In a radioligand binding assay using [3H]CP55,940 in HEK cell membranes transfected with the cannabinoid type 1 receptor (CB1R), MAM‐2201 (Ki = 5.4 nM), similar to WIN 55,212‐2 (Ki = 8.3 nM), had higher binding affinity for CB1R than Δ9‐THC (Ki = 80.1 nM). The Emax values for MAM‐2201 and WIN 55‐212‐2 in an assay of agonist inhibition of forskolin‐stimulated cAMP were 85% (EC50 = 0.45 nM) and 94%, respectively, as compared with the Δ9‐THC Emax of 74%. In mice, MAM‐2201 (0.003‐1.0 mg/kg, I.P., N=8 per group) produced dose‐dependent effects in all measures of the cannabinoid tetrad, which were both more potent and more effective than those of Δ9‐THC. MAM‐2201 and Δ9‐THC dose‐dependently produced the following cannabinoid‐like effects (1) hypothermia: ED50 = 0.287 and 25.4 mg/kg, (2) analgesia: ED50 = 0.125 and 29.4 mg/kg, (3) catalepsy: ED50 = 0.301 and 18.9 mg/kg, and (4) hypolocomotion: ED50 = 0.782 and &gt;100 mg/kg, respectively in adult male CD1 mice. Pronounced strain differences between CD1 and C57Bl6/J animals were noted for hypolocomotor effects, and the CB1 antagonist rimonabant attenuated all of these effects. In rats, MAM‐2201 produced dose‐dependent Δ9‐THC‐like interoceptive effects in subjects trained to discriminate 3.0 mg/kg (IP) Δ9‐THC from saline, and rimonabant attenuated these effects as well. Thus, MAM‐2201 functioned as a potent cannabinoid agonist in vivo across several complementary measures of cannabinoid activity in two rodent species. Importantly, MAM‐2201 also elicited convulsant effects at a dose of 1.0 mg/kg in 8/8 murine subjects. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Drug Enforcement Administration or the Food and Drug Administration.Support or Funding InformationSupported by the Drug Enforcement Administration, National Center for Toxicological Research (protocol # E0763601) and University of Arkansas for Medical Sciences.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cannabinoids induce apathetic and impulsive patterns of choice through CB1 receptors and TRPV1 channels

Despite evidence from psychiatry and psychology clinics pointing to altered cognition and decision making following the consumption of cannabis, the effects of cannabis derivatives are still under dispute and the mechanisms of cannabinoid effects on cognition are not known. In this study, we used effort-based and delay-based decision tasks and showed that ACEA, a potent cannabinoid agonist induced apathetic and impulsive patterns of choice in rats in a dose-dependent manner when locally injected into the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC), respectively. Pre-treatment with AM251, a selective cannabinoid type 1 (CB1) receptor antagonist, reversed ACEA-induced impulsive and apathetic patterns of choice in doses higher than a minimally effective dose. Unlike CB1 receptor antagonist, pretreatment with capsazepine, a transient receptor potential vanilloid type 1 (TRPV1) channel antagonist, was effective only at an intermediary dose. Furthermore, capsazepine per se induced impulsivity and apathy at a high dose suggesting a basal tonic activation of TRPV1 channels that exist in the ACC and OFC to support cost-benefit decision making and to help avoid apathetic and impulsive patterns of decision making. Taken together, unlike previous reports supporting opposing roles for the CB1 receptors and TRPV1 channels in anxiety and panic behavior, our findings demonstrate a different sort of interaction between endocannabinoid and endovanilloid systems and suggest that both systems contribute to the cognitive disrupting effects of cannabinoids. Given prevalent occurrence of apathy and particularly impulsivity in psychiatric disorders, these results have significant implications for pharmacotherapy research targeting these receptors.

Chronic cannabinoid agonist (WIN 55,212-2) exposure alters hippocampal dentate gyrus spine density in adult rats

Chronic abuse of drugs can result in vast negative repercussions on behavioral and biological systems by altering underlying neurocircuitry. Long-term cannabinoid administration in rats leads to detrimental cellular and dendritic morphology changes. Previous studies have found that chronic treatment with delta-9-THC selectively decreases dendritic morphology and spine density in the dentate gyrus of adolescent rats (Rubino et al., 2009); however, whether these changes are specific to a particular developmental age is not known. The present study evaluated the effects of chronic exposure (7 or 21 days) to WIN 55,212-2 (i.p., 3.7mg/kg), a potent cannabinoid agonist, on dendritic morphology of dentate gyrus neurons in adult rats. Upon completion of treatment brains were processed for Golgi–Cox staining. No significant effects of WIN 55,212-2 exposure were observed for dendritic branching or length. Spine density was quantified in the inner (proximal), middle, and outer (distal) thirds of the dendritic fields selected to approximate the spatial loci of afferents comprising the associational–commissural pathway, medial perforant path, and lateral perforant path, respectively. Compared to vehicle controls there was a significant reduction in spine density (~1 spine/10μm) in the inner and middle dendritic segments. The spine density reduction was significant in inner segments following 7 days of treatment. These results suggest that chronic cannabinoid treatment specifically alters spine density in the dendritic targets of the associational–commissural afferents and medial perforant path projections, but not lateral perforant path. The resulting loss of dendritic spine density may be an important factor underlying cannabinoid induced memory impairments.

Behavioral effects of the novel potent cannabinoid CB1 agonist AM 4054

Due to the ubiquity of the CB1 cannabinoid receptor throughout the nervous system, as well as the many potential therapeutic uses of CB1 agonist-based interventions, it is desirable to synthesize novel probes of the CB1 receptor. Here, the acute behavioral effects of systemic (i.p.) administration of the putative novel CB1 full agonist AM 4054 were tested in rats. In Experiment 1, a dose range (0.15625–1.25mg/kg) of AM 4054 produced effects consistent with CB1 agonism in the cannabinoid tetrad of tasks in rats, including induction of analgesia, catalepsy, hypothermia, and locomotor suppression. These effects were reversed with the CB1-selective inverse agonist AM 251 in Experiment 2, indicating that AM 4054 produced CB1 receptor-mediated effects. Analysis of open-field activity indicated that the reduction in locomotion is more consistent with general motor slowing than anxiogenesis. AM 4054 (0.0625–0.5mg/kg) also dose-dependently reduced fixed-ratio 5 (FR5) operant responding for food in Experiment 3, and microanalysis of the timing and rate of lever pressing indicated a pattern of suppression similar to other CB1 agonists. Minimum doses of AM 4054 (0.125–0.3125mg/kg) required to produce significant effects in these behavioral assays were lower than those of many CB1 agonists. It is likely that AM 4054 is a potent pharmacological tool for assessment of cannabinoid receptor function.

Long-term CB1 receptor blockade enhances vulnerability to anxiogenic-like effects of cannabinoids

Compelling evidence has documented the anxiolytic and mood-enhancing properties of cannabis. In susceptible users, however, consumption of this drug is conducive to panic, paranoia and dysphoria. We hypothesized that the up-regulation of CB1 receptors (CB1Rs) in select brain regions may enhance the vulnerability to cannabinoid-induced anxiety. To test this possibility, we assessed the behavioral impact of a potent cannabinoid agonist (CP55,940; 0.05–0.1 mg/kg, IP) on C57BL/6 male mice, respectively subjected to a prolonged pre-treatment of either the selective CB1R antagonist/inverse agonist AM251 (1 mg/kg/day IP, for 21 days, followed by a 3-day clearance period before testing) or its vehicle (VEH1). Anxiety-like responses were studied in the novel open field, elevated plus maze (EPM) and social interaction assays. While CP55,940 induced anxiolytic-like effects in the EPM in VEH1-exposed animals, it elicited opposite actions in AM251-exposed mice. In this last group, CP55,940 also reduced rearing and social interaction in comparison to its vehicle (VEH2). The divergent effects of CP55,940 in AM251- and VEH1-pretreated animals were confirmed in 129SvEv mice. Immunoblotting analyses on brain samples of C57BL/6 mice revealed that AM251 pre-treatment caused a significant up-regulation of CB1R expression in the prefrontal cortex and striatum, but also a down-regulation of these receptors in the hippocampus and midbrain. Notably, CB1R levels in the prefrontal cortex were negatively correlated with anxiolysis-related indices in the EPM; furthermore, midbrain CB1R expression was positively correlated with the total duration of social interaction. These results suggest that regional variations in brain CB1R expression may differentially condition the behavioral effects of cannabinoids with respect to anxiety-related responses.

Intrahippocampal cannabinoid administration induces antinociceptive and amnestic response

In the present study, the possible role of a potent cannabinoid agonist, WIN55, 212-2 in the dorsal hippocampus on pain and memory performance has been evaluated. Animals were cannulated in CA1 region of the hippocampus using sterotaxic apparatus. Ten days after recovery, animals were trained in passive avoidance learning (PAL), and immediately received different doses of WIN 55212-2 (0.1, 0.25 and 0.5µg/rat), and were tested 24 h after the training. In the second part of the experiment animals received either WIN 55212-2 (0.5µg/rat) or saline respectively. Tail flick latency was measured three times with 10 minutes interval 30 minutes and 24 hours after the infusion into the CA1. Results indicate that post-training intra-CA1 administration of WIN55, 212-2 (0.25 and 0.5µg/rat) (P< 0.001) reduced step-down latency, showing an amnestic response. Also microinjection of WIN55212-2 (0.5ug/kg) into the CA1 region of the hippocampus induced analgesia compared to control group) (P< 0.01).

Differential Treatment Regimen-Related Effects of HU210 on CB1 and D2-Like Receptor Functionality in the Rat Basal Ganglia

Background/Aims: Functional linkages between the cannabinoid CB₁ and the dopaminergic systems have been reported although the observations and the mechanisms hypothesizing their interactions at the G protein-coupled receptor (GPCR) functionality level are conflicting. Methods: Administration of a potent cannabinoid agonist, HU210, at various doses (25–100 µg/kg) and treatment regimens (1- to 14-day treatment) in rats was carried out to investigate the effect of HU210 treatment on the CB₁ and D₂-like agonist-mediated GPCR activation. Results: The desensitizations (reduced coupling) of both D₂ agonist- and CB₁ agonist-mediated GPCR activation was found to be treatment duration dependent and region specific, suggesting implication of receptor tolerance and adaptation due to the cannabinoid treatment. The effect of HU210 on the CB₁ agonist-mediated GPCR desensitization in all treatment groups was not dose dependent. Conclusions: The desensitization of D₂-like receptors found after a cannabinoid treatment in this study strengthens the evidence that the two neurotransmitter systems interact at the intercellular level; this interaction might occur via multiple mechanisms, which also vary according to region.

Methamphetamine neurotoxicity increases brain expression and alters behavioral functions of CB 1 cannabinoid receptors

Cannabis is the most common secondary illicit substance in methamphetamine (METH) users, yet the outcomes of the concurrent consumption of both substances remain elusive. Capitalizing on recent findings on the implication of CB 1 cannabinoid receptors in the behavioral effects of METH, we hypothesized that METH-induced neurotoxicity may alter the brain expression of CB 1, thereby affecting its role in behavioral functions. To test this possibility, we subjected rats to a well-characterized model of METH neurotoxicity (4 mg/kg, subcutaneous × 4 injections, 2 h apart), and analyzed their CB 1 receptor brain expression three weeks later. METH exposure resulted in significant enhancements of CB 1 receptor expression across several brain regions, including prefrontal cortex, caudate-putamen, basolateral amygdala, CA1 hippocampal region and perirhinal cortex. In parallel, a different group of METH-exposed rats was used to explore the responsiveness to the potent cannabinoid agonist WIN 55,212–2 (WIN) (0.5–1 mg/kg, intraperitoneal), within several paradigms for the assessment of emotional and cognitive functions, such as open field, object exploration and recognition, and startle reflex. WIN induced anxiolytic-like effects in METH-exposed rats and anxiogenic-like effects in saline-treated controls. Furthermore, METH-exposed animals exhibited a significantly lower impact of WIN on the attenuation of exploratory behaviors and short-term (90 min) recognition memory. Conversely, METH neurotoxicity did not significantly affect WIN-induced reductions in locomotor activity, exploration time and acoustic startle. These results suggest that METH neurotoxicity may alter the vulnerability to select behavioral effects of cannabis, by inducing distinct regional variations in the expression of CB 1 receptors.

The antinociceptive effect of acetylsalicylic acid is differently affected by a CB 1 agonist or antagonist and involves the serotonergic system in rats

Aims Combinations of non-steroidal anti-inflammatory drugs (NSAIDs) and cannabinoids are promising because of their potential synergistic effects in analgesia, resulting in a reduction in dosage and minimizing adverse reactions. The analgesic effect of acetylsalicylic acid (ASA), probably due to a central mechanism, also implicates changes in the central monoaminergic system. Therefore, we decided to evaluate the antinociceptive interaction between the CB 1 receptor agonist, HU210, and ASA in tests involving central pain in rats as well as the implication of the central serotonergic system thereon. Main methods The selective CB 1 antagonist SR141716A and the potent cannabinoid agonist HU210 were evaluated alone and in combination with ASA in both algesimetric tests (hot-plate and formalin tests) and for 5-HT activity and 5-HT 2 receptor density and affinity. Key findings ASA or HU210 alone showed a dose-dependent effect in both tests. HU210, at an inactive dose, significantly increased the antinociceptive effect of the sub-active dose of ASA. SR141716A (1.5 mg/kg i.p.) was ineffective per se and failed to modify antinociception induced by the HU210 plus ASA combination in either test. HU210 plus ASA significantly decreased the 5-HIAA/5-HT ratio and the 5-HT 2 receptor density in the frontal cortex, changes not antagonized by SR141716A. Significance The present study provides evidence that mutual potentiation of the antinociceptive effects of HU210 and ASA may, at least partly, depend on serotonergic mechanisms, with an indirect participation of cannabinodiergic mechanism. In conclusion, combinations of low doses of cannabinoids and NSAIDs may be of interest from the therapeutic point of view.

HU210-Induced Downregulation in Cannabinoid CB1 Receptor Binding Strongly Correlates with Body Weight Loss in the Adult Rat

In vitro autoradiography was used to examine changes in cannabinoid CB1 receptors (targeted with [(3)H] CP55,940) in rats treated with the potent cannabinoid agonist HU210. Animals were administered with HU210 (25, 50, 100 microg/kg) for 4 or 14 days or received a single 100 microg/kg injection of HU210 and sacrificed 24 h later. The acute dose resulted in a decrease in binding in the caudate putamen and hippocampus. A dose dependent, region-specific reduction (P < 0.0001) in [(3)H] CP55,940 binding was seen in all brain regions examined after 4 and 14 days treatment. A decrease in body weight was recorded during the first 4 days of treatment but after this animals began to gain weight. Correlations (0.865 < r < 0.659, P < 0.0001) between body weight on day four and CB1 receptor binding were found in all brain regions examined suggesting that downregulation of CB1 receptors may contribute to the induction of tolerance to body weight loss induced by HU210.

Chronic treatment and withdrawal of the cannabinoid agonist WIN 55,212-2 modulate the sensitivity of presynaptic receptors involved in the regulation of monoamine syntheses in rat brain

Brain monoamines are involved in many neurochemical and behavioral effects of cannabinoids, but little is known on the regulation of noradrenaline, dopamine, and serotonin (5-HT) synthesis in cannabinoid addiction. This study investigated in rat brain the chronic effects of the potent cannabinoid agonist WIN 55,212-2 and of rimonabant-precipitated withdrawal, as well as the sensitivity of synthesis-modulating inhibitory receptors, on the accumulation of L-3,4-dihydroxyphenylalanine (DOPA) and 5-HTP after decarboxylase inhibition. Acute WIN (8 mg/kg; 1 h) increased DOPA synthesis in cortex (52%), hippocampus (51%), and cerebellum (56%) and decreased DOPA accumulation in striatum (31%). Acute WIN also decreased the synthesis of 5-HTP in all brain regions (40-53%). Chronic WIN (2-8 mg/kg; 5 days) and/or antagonist-precipitated withdrawal induced tolerance to the acute effects of WIN on the accumulation of DOPA (cortex and striatum) and 5-HTP (all brain regions). The inhibitory effect of clonidine (alpha2-agonist; 1 mg/kg) on the accumulation of DOPA (15-41%) and 5-HTP (22-41%) was markedly decreased or abolished after chronic WIN and precipitated withdrawal, mainly in noradrenergic and serotonergic brain regions, which indicated desensitization of alpha2-autoreceptors and alpha2-heteroreceptors regulating the synthesis of noradrenaline and 5-HT. In WIN-dependent rats (chronic and withdrawal states), the effect of a low dose of (+/-)-8-hydroxy-2-(di-n-propylamino)-tetralin (5-HT1A agonist; 0.1 mg/kg) on the accumulation of precursor amino acids was markedly potentiated in cerebellum and striatum, indicating the induction of supersensitivity of 5-HT1A-autoreceptors and 5-HT1A-heteroreceptors that regulate the synthesis of 5-HT, noradrenaline, and dopamine in these brain regions. These chronic adaptations in presynaptic receptor function could play a relevant role in cannabinoid addiction.

Behavioural effects of quinpirole following withdrawal of chronic treatment with the CB1 agonist, HU-210, in rats

The present study investigated spontaneous and quinpirole-induced motor responses of in rats, following withdrawal from chronic treatment with the potent cannabinoid agonist HU-210. Withdrawal from chronic HU-210 (20 microg/kg daily, 14 days) produced a decrease in spontaneous activity at 1 and 2 days and enhanced the hyperactivity induced by acute administration of the dopamine D2 agonist quinpirole (0.5 mg/kg) at 4 days after the end of HU-210 treatment. Administration of quinpirole on day 4 of withdrawal from chronic HU-210 enhanced stereotyped responses and induced jumping behaviour. These results suggest that withdrawal from chronic exposure to cannabinoid agonists could induce a time-dependent alteration in dopamine D2 psychomotor function, leading to a behavioural disorganization, comparable to acute psychotic episodes after continuous cannabinoids.

Cannabinoid modulation of sensitivity to time

The present studies used a psychophysical approach to examine the effect of cannabinoids on temporal processing. Rats trained to discriminate 2- and 8-s (Experiment 1, n=72) and 4- and 16-s (Experiment 2, n=60) intervals were tested with intermediate durations. Psychophysical functions for time, relating the probability of judging a duration as “long” as a function of the actual stimulus durations, were characterized by measures of central tendency (point of subjective equality, PSE) and variability (Weber fraction, WF). The potent cannabinoid agonist, WIN55,212-2 (1–3 mg/kg), produced a dose-related decrease in sensitivity to time (i.e. increase in WF) without systematically affecting PSE (Experiments 1 and 2). The central cannabinoid CB1 antagonist, SR141716A (1–3 mg/kg), did not alter either the WF or PSE (Experiments 1 and 2). Coadministration of SR141716A with WIN55,212-2 blocked the effect of the agonist on WF (Experiment 2), suggesting that the WF effect is mediated by actions at cannabinoid CB1 receptors. Computational modeling with an information processing theory of timing suggests that the reduction in sensitivity to time can be attributed to a disorder of attention.

Differential cannabinoid-induced electrophysiological effects in rat ventral tegmentum

Cannabinoids are known to exert mainly excitatory effects on dopaminergic cells of the ventral tegmental area (VTA). We have utilized an in vivo multiple-single unit electrophysiological approach to assess different neuronal contributions that may ultimately lead to excitation in this area. Baseline neuron recordings, using low impedance microwires, showed a variety of waveforms with a wide range of durations (0.8–3.2 ms). In the first experiment systemic injection of the potent cannabinoid agonist HU210 (100 μg/kg, i.p.) led predominantly to an increase in firing rate (~214%, compared to pre-drug) in slowly firing cells with broad action potentials, possibly driven by a majority of presumed dopaminergic neurons ( n = 31). However, the firing rate of some units was either unaffected (<25%, n = 9) or even decreased (~67%, n = 9) following cannabinoid injection concomitantly with excitation. Apomorphine (75 μg/kg, i.p.) injected following HU210 produced a marked inhibition of both responses (~76%) in 39 out of 49 cells. The second group of animals was treated with the CB 1 receptor antagonist SR141716A (1 mg/kg, i.p.), which had no effect when injected alone but prevented all HU210-evoked changes in firing rate suggesting that cannabinoid receptors mediated the observed responses ( n = 39). Taken together, the present results suggest that the observed actions of cannabinoids may involve complex neurotransmitter interactions leading to differential effects on dopamine release. These heterogeneous neuronal responses are likely to underly the behavioural discrepancies reported in animal models of cannabinoid reinforcement.

Synthesis and characterization of the potent cannabinoid agonist [naphthyl‐3H] WIN 55212‐2 at high specific activity

Abstract[Naphthyl‐3H] WIN 55212‐2 was prepared at high specific activity by the catalytic tritiation of dibromo precursor 3. Product 4 was characterized by chromatography as well as tritium NMR and proven to be a useful radioligand. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Evidence that anandamide-signaling regulates human sperm functions required for fertilization.

Ejaculated mammalian sperm require several hours exposure to secretions in female reproductive tracts, or incubation in appropriate culture medium in vitro, before acquiring the capacity to fertilize eggs. Arachidonylethanolamide (AEA), also known as anandamide, is a novel lipid-signal molecule that is an endogenous agonist (endocannabinoid) for cannabinoid receptors. We now report that AEA is present in human seminal plasma, mid-cycle oviductal fluid, and follicular fluid analyzed by high-performance liquid chromatography/mass spectrometry. Sperm are sequentially exposed to these reproductive fluids as they move from the vagina to the site of fertilization in the oviduct. Specific binding of the potent cannabinoid agonist [(3)H]CP-55,940 to human sperm was saturable (K(D) 9.71 +/- 1.04 nM), suggesting that they express cannabinoid receptors. R-methanandamide [AM-356], a potent and metabolically stable AEA analog, and (-)delta(9) tetrahydrocannabinol (THC), the major psychoactive constituent of Cannabis, modulated capacitation and fertilizing potential of human sperm in vitro. AM-356 elicited biphasic effects on the incidence of hyperactivated sperm motility (HA) between 1 and 6 hr of incubation: at (2.5 nM) it inhibited HA, while at (0.25 nM) it stimulated HA. Both AM-356 and THC inhibited morphological alterations over acrosomal caps between 2 and 6 hr (IC(50) 5.9 +/- 0.6 pM and 3.5 +/- 1.5 nM, respectively). Sperm fertilizing capacity, measured in the Hemizona Assay, was reduced 50% by (1 nM) AM-356. These findings suggest that AEA-signaling may regulate sperm functions required for fertilization in human reproductive tracts, and imply that smoking of marijuana could impact these processes. This study has potential medical and public policy ramifications because of the incidence of marijuana abuse by adults in our society, previously documented reproductive effects of marijuana, and the ongoing debate about medicinal use of marijuana and cannabinoids.