The use of Cannabis sativa by humans dates back several thousand years, for both its psychotomimetic and potential medicinal properties. As scientific research methods developed, the cannabinoids present in this herb were characterized, as well as their complex interface with the human central nervous system, provided by the activation of specific receptors. The subsequent description of an endogenous cannabinoid system in the mammalian brain shifted the notion of cannabis as a recreational drug to a therapeutic alternative for psychiatric disorders. However, the neuroanatomical sites mediating its effects have remained uncertain. In the present paper, we review recent data suggesting that the midbrain periaqueductal gray may be a structure involved in the anxiolytic-like effects of cannabinoids.

OBJETIVO: Este artigo revisa o sistema endocanabinoide e as respectivas estratégias de intervenções farmacológicas. MÉTODO: Realizou-se uma revisão da literatura sobre o sistema endocanabinoide e a sua farmacologia, considerando-se artigos originais ou de revisão escritos em inglês. DISCUSSÃO: Canabinoides são um grupo de compostos presentes na Cannabis Sativa (maconha), a exemplo do Δ9-tetraidrocanabinol e seus análogos sintéticos. Estudos sobre o seu perfil farmacológico levaram à descoberta do sistema endocanabinoide do cérebro de mamíferos. Este sistema é composto por pelo menos dois receptores acoplados a uma proteína G, CB1 e CB2, pelos seus ligantes endógenos (endocanabinoides; a exemplo da anandamida e do 2-araquidonoil glicerol) e pelas enzimas responsáveis por sintetizá-los e metabolizá-los. Os endocanabinoides representam uma classe de mensageiros neurais que são sintetizados sob demanda e liberados de neurônios pós-sinápticos para restringir a liberação de neurotransmissores clássicos de terminais pré-sinápticos. Esta sinalização retrógrada modula uma diversidade de funções cerebrais, incluindo ansiedade, medo e humor, em que a ativação de receptores CB1 pode exercer efeitos dos tipos ansiolítico e antidepressivo em estudos préclínicos. CONCLUSÃO: Experimentos com modelos animais sugerem que drogas que facilitam a ação dos endocanabinoides podem representar uma nova estratégia para o tratamento de transtornos de ansiedade e depressão.

OBJECTIVE: The present review provides a brief introduction into the endocannabinoid system and discusses main strategies of pharmacological interventions. METHOD: We have reviewed the literature relating to the endocannabinoid system and its pharmacology; both original and review articles written in English were considered. DISCUSSION: Cannabinoids are a group of compounds present in Cannabis Sativa (hemp), such as Δ9-tetrahydrocannabinol, and their synthetic analogues. Research on their pharmacological profile led to the discovery of the endocannabinoid system in the mammalian brain. This system comprises at least two G-protein coupled receptors, CB1 and CB2, their endogenous ligands (endocannabinoids; e.g. the fatty acid derivatives anandamide and 2-arachydonoyl glycerol), and the enzymes responsible for endocannabinoid synthesis and catabolism. Endocannabinoids represent a class of neuromessengers, which are synthesized on demand and released from post-synaptic neurons to restrain the release of classical neurotransmitters from pre-synaptic terminals.This retrograde signalling modulates a variety of brain functions, including anxiety, fear and mood, whereby activation of CB1 receptors was shown to exert anxiolytic-and antidepressant-like effects in preclinical studies. CONCLUSION: Animal experiments suggest that drugs promoting endocannabinoid action may represent a novel strategy for the treatment of depression and anxiety disorders.