CB1 and CB2 receptors in the bed nucleus of the stria terminalis differently modulate anxiety-like behaviors in rats

Abstract

The endocannabinoid system is implicated in anxiety, but the brain sites involved are not completely understood. The bed nucleus of the stria terminalis (BNST) has been related to anxiety and responses to aversive threats. Besides, endocannabinoid neurotransmission acting via CB1 receptors was identified in the BNST. However, the presence of CB2 receptors and the role of BNST endocannabinoid system in anxiety-like behaviors have never been reported. Therefore, this study investigated the presence of CB1 and CB2 receptors in the BNST and their role in anxiety-like behaviors. For this, gene expression of the endocannabinoid receptors was evaluated in samples from anterior and posterior BNST. Besides, behaviors were evaluated in the elevated plus-maze (EPM) in unstressed rats (trait anxiety-like behavior) and after exposure to restraint stress (restraint-evoked anxiety-like behavior) in rats treated with either the CB1 receptor antagonist AM251 or the CB2 receptor antagonist JTE907 into the anterior BNST. The presence of CB1 and CB2 receptors gene expression was identified in anterior and posterior divisions of the BNST. Bilateral microinjection of AM251 into the anterior BNST dose-dependently increased EPM open arms exploration in unstressed animals and inhibited the anxiety-like behavior in the EPM evoked by restraint. Conversely, intra-BNST microinjection of JTE907 decreased EPM open arms exploration in a dose-dependent manner and inhibited restraint-evoked behavioral changes in the EPM. Taken together, these results indicate that CB1 and CB2 receptors present in the BNST are involved in control of anxiety-like behaviors, and control by the latter is affected by previous stress experience.