Cannabinoid CB2 receptor: a new target for controlling neural cell survival?

Two types of cannabinoid receptor have been cloned and characterized. Whereas CB1 receptors are ubiquitously expressed in neurons of the CNS, CB2 receptors have been thought to be absent from the CNS. Recent data now question this notion and support the expression of CB2 receptors in microglial cells, astrocytes and even some neuron subpopulations. This discrete distribution makes CB2 receptors interesting targets for treating neurological disorders because CB2-selective agonists lack psychoactivity. Here, we review evidence supporting the idea that CB2 receptors are implicated in the control of fundamental neural cell processes, such as proliferation and survival, and that their pharmacological manipulation might be useful for both delaying the progression of neurodegenerative disorders and inhibiting the growth of glial tumors.