The endocannabinoid system in the processing of anxiety and fear and how CB1 receptors may modulate fear extinction

The endocannabinoid system recently emerged as an important modulator of many neuronal functions. Among them, the control of anxiety and acquired fear represents nowadays one of the most interesting fields of research. Despite contrasting results obtained by the use of cannabinoid receptor agonists in experimental animals, there is growing evidence that the physiological activation of the endocannabinoid system plays a central role in the control of basal anxiety levels and in the modulation of fear responses. This review will summarise recent data on the role of the endocannabinoid system in most commonly used tests of anxiety and in the processing of acquired fear, with particular attention to its involvement in fear extinction. Finally, a neurobiological model possibly able to implement the role of the endocannabinoid system in these processes will be proposed. (c) 2007 Elsevier Ltd. All rights reserved.