Endocannabinoids regulate interneuron migration and morphogenesis by transactivating the TrkB receptor

The endocannabinoid system as an emerging target of pharmacotherapy

The recent identification of cannabinoid receptors and their endogenous lipid ligands has triggered an exponential growth of studies exploring the endocannabinoid system and its regulatory functions in health and disease. Such studies have been greatly facilitated by the introduction of selective cannabinoid receptor antagonists and inhibitors of endocannabinoid metabolism and transport, as well as mice deficient in cannabinoid receptors or the endocannabinoid-degrading enzyme fatty acid amidohydrolase. In the past decade, the endocannabinoid system has been implicated in a growing number of physiological functions, both in the central and peripheral nervous systems and in peripheral organs. More importantly, modulating the activity of the endocannabinoid system turned out to hold therapeutic promise in a wide range of disparate diseases and pathological conditions, ranging from mood and anxiety disorders, movement disorders such as Parkinson's and Huntington's disease, neuropathic pain, multiple sclerosis and spinal cord injury, to cancer, atherosclerosis, myocardial infarction, stroke, hypertension, glaucoma, obesity/metabolic syndrome, and osteoporosis, to name just a few. An impediment to the development of cannabinoid medications has been the socially unacceptable psychoactive properties of plant-derived or synthetic agonists, mediated by CB(1) receptors. However, this problem does not arise when the therapeutic aim is achieved by treatment with a CB(1) receptor antagonist, such as in obesity, and may also be absent when the action of endocannabinoids is enhanced indirectly through blocking their metabolism or transport. The use of selective CB(2) receptor agonists, which lack psychoactive properties, could represent another promising avenue for certain conditions. The abuse potential of plant-derived cannabinoids may also be limited through the use of preparations with controlled composition and the careful selection of dose and route of administration. The growing number of preclinical studies and clinical trials with compounds that modulate the endocannabinoid system will probably result in novel therapeutic approaches in a number of diseases for which current treatments do not fully address the patients' need. Here, we provide a comprehensive overview on the current state of knowledge of the endocannabinoid system as a target of pharmacotherapy.

Cannabis and neurodevelopment: implications for psychiatric disorders

The developing brain is susceptible to the effects of exogenous cannabinoids both during the perinatal period through maternal cannabis use and in young adolescent users. Emerging data from human and animal perinatal exposure studies demonstrate a subtle rather than gross effect of cannabis upon later functioning including; specific cognitive deficits especially in visuospatial function; impulsivity, inattention and hyperactivity; depressive symptoms; and substance use disorders. From animal studies motor control systems, neuroendocrine function and nociception may additionally be affected. Fetal studies indicate that these outcomes may be through cannabinoid mediated influences on the ontogeny of, especially dopamine and opioid, neurotransmitter systems. The effect of cannabinoids in the adolescent suggest long-term deleterious outcomes in cognition, depressive symptoms, schizophrenia and substance use disorders. Much of these data support a neurodevelopmental effect, however, predisposing genetic and/or environmental factors cannot be excluded from human studies. Gender specific differences have been observed in both human and animal studies implying sex hormone and related factors may interact with cannabinoids in neurodevelopment. Further understanding how cannabinoids influence neurodevelopment will inform public debate about the health effects of cannabis but also open avenues in discerning how modulation of the endocannabinoid system may assist in the development of therapeutic tools for a variety of neuropsychiatric disorders.