Role of CB2 receptors in neuroprotective effects of cannabinoids.

CB2 receptors, the so-called peripheral cannabinoid receptor type, were first described in the immune system, but they have been recently identified in the brain in healthy conditions and, in particular, after several types of cytotoxic stimuli. Specifically, CB2 receptors were identified in microglial cells, astrocytes and, to a lesser extent, in certain subpopulations of neurons. Given the lack of psychoactivity demonstrated by selective CB2 receptor agonists, this receptor becomes an interesting target for the treatment of neurological diseases, in particular, the case of certain neurodegenerative disorders in which induction/up-regulation of CB2 receptors has been already demonstrated. These disorders include Alzheimer's disease, Huntington's chorea, amyotrophic lateral sclerosis and others. Interestingly, in experimental models of these disorders, the activation of CB2 receptors has been related to a delayed progression of neurodegenerative events, in particular, those related to the toxic influence of microglial cells on neuronal homeostasis. The present article will review the evidence supporting that CB2 receptors might represent a key element in the endogenous response against different types of cytotoxic events, and that this receptor type may be a clinically promising target for the control of brain damage in neurodegenerative disorders.