From Active Ingredients to the Discovery of the Targets: The Cannabinoid Receptors

Potency trends of Δ9-THC and other cannabinoids in confiscated cannabis preparations from 1993 to 2008

The University of Mississippi has a contract with the National Institute on Drug Abuse (NIDA) to carry out a variety of research activities dealing with cannabis, including the Potency Monitoring (PM) program, which provides analytical potency data on cannabis preparations confiscated in the United States. This report provides data on 46,211 samples seized and analyzed by gas chromatography-flame ionization detection (GC-FID) during 1993-2008. The data showed an upward trend in the mean Δ(9)-tetrahydrocannabinol (Δ(9)-THC) content of all confiscated cannabis preparations, which increased from 3.4% in 1993 to 8.8% in 2008. Hashish potencies did not increase consistently during this period; however, the mean yearly potency varied from 2.5-9.2% (1993-2003) to 12.0-29.3% (2004-2008). Hash oil potencies also varied considerably during this period (16.8 ± 16.3%). The increase in cannabis preparation potency is mainly due to the increase in the potency of nondomestic versus domestic samples.

Neurobiologia da Cannabis: do sistema endocanabinoide aos transtornos por uso de Cannabis

OBJETIVOS: Diante das lacunas na efetividade das terapêuticas para transtornos por uso de Cannabis, a droga ilícita mais consumida no mundo, este trabalho propõe-se a rever os conhecimentos sobre o substrato neuroanatômico, biomolecular e celular do sistema endocanabinoide, descrever os mecanismos de neuroplasticidade dependente dos canabinoides e relacioná-los com a neurobiologia dos transtornos por uso de Cannabis (abuso e dependência). MÉTODOS: Recorreu-se às bases de dados Medline, Scopus e ISI Web of Knowledge; as palavras-chave pesquisadas foram "Cannabis", "neurobiology", "endocannabinoid system", "endocannabinoids", "receptors, cannabinoid", "neuronal plasticity", "long-term synaptic depression", "long-term potentiation", "marijuana abuse" e "tetrahydrocannabinol". Foram incluídos 80 trabalhos nesta revisão. DISCUSSÃO: A distribuição neuroanatômica, celular e biomolecular do sistema endocanabinoide adequa-se perfeitamente às suas funções de neuromodulação (via neuroplasticidade e metaplasticidade), nomeadamente em vias relacionadas aos transtornos por uso de substâncias. Os canabinoides exógenos perturbam essas funções. CONCLUSÃO: O sistema endocanabinoide contribui para a definição de setpoints em diversas vias neuronais, incluindo vias cruciais na instalação de transtornos por uso de substâncias; com o uso de Cannabis, esses setpoints tornar-se-ão mais permissivos, facilitando os transtornos por uso de Cannabis. Os avanços no entendimento da neurobiologia da Cannabis abrem uma janela de oportunidades para novas estratégias terapêuticas nos transtornos por uso de Cannabis.

Cannabinoid receptor activation reduces TNFalpha-induced surface localization of AMPAR-type glutamate receptors and excitotoxicity

After injury or during neurodegenerative disease in the central nervous system (CNS), the concentration of tumor necrosis factor alpha (TNFalpha) rises above normal during the inflammatory response. In vitro and in vivo, addition of exogenous TNFalpha to neurons has been shown to induce rapid plasma membrane-delivery of AMPA-type glutamate receptors (AMPARs) potentiating glutamatergic excitotoxicity. Thus the discovery of drug targets reducing excess TNFalpha-induced AMPAR surface expression may help protect neurons after injury. In this study, we investigate the neuroprotective role of the CB1 cannabinoid receptor using quantitative immunofluorescent and real-time video microscopy to measure the steady-state plasma membrane AMPAR distribution and rate of AMPAR exocytosis after TNFalpha exposure in the presence or absence of CB1 agonists. The neuroprotective potential of CB1 activation with TNFalpha was measured in hippocampal neuron cultures challenged by an in vitro kainate (KA)-mediated model of Excitotoxic Neuroinflammatory Death (END). Here, we demonstrate that CB1 activation blocks the TNFalpha-induced increase in surface AMPARs and protects neurons from END. Thus, neuroprotective strategies which increase CB1 activity may help to reduce the END that occurs as a result of a majority of CNS insults.

Altered surface trafficking of presynaptic cannabinoid type 1 receptor in and out synaptic terminals parallels receptor desensitization

Presynaptic cannabinoid type 1 receptors (CB1Rs) are major mediators of retrograde synaptic plasticity at both excitatory and inhibitory synapses and participate in a plethora of physiological functions. Whether presynaptic receptors, such as CB1R, display functionally relevant movements at the surface of neuronal membranes is not known. We analyzed the lateral mobility of native CB1Rs in cortical neurons by using single-quantum dot imaging. We found that CB1Rs are highly mobile and rapidly diffuse in and out of presynapses. Agonist-induced desensitization correlated with a reduction in the fraction of surface CB1Rs and a drastic decrease in the membrane dynamic of the CB1Rs that remained at the presynaptic surface. Desensitization specifically excluded CB1Rs from synapses and increased the fraction of immobile receptors in the extrasynaptic compartment. The results suggest that decrease of mobility may be one of the core mechanisms underlying the desensitization of CB1R, the most abundant G protein-coupled receptor in the brain.