Cannabinoid CB1 receptors in the dorsal hippocampus and prelimbic medial prefrontal cortex modulate anxiety-like behavior in rats: additional evidence.

“Endocannabinoids (ECBs) such as anandamide (AEA) act by activating cannabinoid type 1 (CB1) or 2 (CB2) receptors. The anxiolytic effect of drugs that facilitate ECB effects is associated with increase in AEA levels in several encephalic areas, including the prefrontal cortex (PFC).

Activation of CB1 receptors by CB1 agonists injected directly into these areas is usually anxiolytic.

However, depending on the encephalic region being investigated and on the stressful experiences, opposite effects were observed, as reported in the ventral HIP. In addition, contradictory results have been reported after CB1 activation in the dorsal HIP (dHIP).

Therefore, in the present paper we have attempted to verify if directly interfering with ECB metabolism/reuptake in the prelimbic (PL) portion of the medial PFC (MPFC) and dHIP would produce different effects in two conceptually distinct animal models: the elevated plus maze (EPM) and the Vogel conflict test (VCT).

We observed drugs which interfere with ECB reuptake/metabolism in both the PL and in the dentate gyrus of the dHIP induced anxiolytic-like effect, in both the EPM and in the VCT via CB1 receptors, suggesting CB1 signaling in these brain regions modulate defensive responses to both innate and learned threatening stimuli.

This data further strengthens previous results indicating modulation of hippocampal and MPFC activity via CB1 by ECBs, which could be therapeutically targeted to treat anxiety disorders.”

Cannabinoids and anxiety.

“The term cannabinoids encompasses compounds produced by the plant Cannabis sativa, such as delta9-tetrahydrocannabinol, and synthetic counterparts. Their actions occur mainly through activation of cannabinoid type 1 (CB1) receptors. Arachidonoyl ethanolamide (anandamide) and 2-arachidonoyl glycerol (2-AG) serve as major endogenous ligands (endocannabinoids) of CB1 receptors. Hence, the cannabinoid receptors, the endocannabinoids, and their metabolizing enzymes comprise the endocannabinoid system. Cannabinoids induce diverse responses on anxiety- and fear-related behaviors. Generally, low doses tend to induce anxiolytic-like effects, whereas high doses often cause the opposite. Inhibition of endocannabinoid degradation seems to circumvent these biphasic effects by enhancing CB1 receptor signaling in a temporarily and spatially restricted manner, thus reducing anxiety-like behaviors. Pharmacological blockade or genetic deletion of CB1 receptors, in turn, primarily exerts anxiogenic-like effects and impairments in extinction of aversive memories. Interestingly, pharmacological blockade of Transient Receptor Potential Vanilloid Type-1 (TRPV1) channel, which can be activated by anandamide as well, has diametrically opposite consequences. This book chapter summarizes and conceptualizes our current knowledge about the role of (endo)cannabinoids in fear and anxiety and outlines implications for an exploitation of the endocannabinoid system as a target for new anxiolytic drugs.”

The endocannabinoid system in anxiety, fear memory and habituation.

“Evidence for the involvement of the endocannabinoid system (ECS) in anxiety and fear has been accumulated, providing leads for novel therapeutic approaches. In anxiety, a bidirectional influence of the ECS has been reported, whereby anxiolytic and anxiogenic responses have been obtained after both increases and decreases of the endocannabinoid tone. The recently developed genetic tools have revealed different but complementary roles for the cannabinoid type 1 (CB1) receptor on GABAergic and glutamatergic neuronal populations. This dual functionality, together with the plasticity of CB1 receptor expression, particularly on GABAergic neurons, as induced by stressful and rewarding experiences, gives the ECS a unique regulatory capacity for maintaining emotional homeostasis. However, the promiscuity of the endogenous ligands of the CB1 receptor complicates the interpretation of experimental data concerning ECS and anxiety. In fear memory paradigms, the ECS is mostly involved in the two opposing processes of reconsolidation and extinction of the fear memory. Whereas ECS activation deteriorates reconsolidation, proper extinction depends on intact CB1 receptor signalling. Thus, both for anxiety and fear memory processing, endocannabinoid signalling may ensure an appropriate reaction to stressful events. Therefore, the ECS can be considered as a regulatory buffer system for emotional responses.”

Pharmacological Evaluation of Cannabinoid Receptor Ligands in a Mouse Model of Anxiety: Further Evidence for an Anxiolytic Role for Endogenous Cannabinoid Signaling

“Extracts of Cannabis sativa have been used for their calming and sedative effects for centuries. Recent developments in drug discovery have suggested that modulation of neuronal endogenous cannabinoid signaling systems could represent a novel approach to the treatment of anxiety-related disorders while minimizing the adverse effects of direct acting cannabinoid receptor agonists. In this study, we evaluated the effects of direct cannabinoid receptor agonists and antagonists and endocannabinoid-modulating drugs on anxiety-like behavior in mice using the elevated-plus maze.

These data indicate that activation of CB1 cannabinoid receptors reduces anxiety-like behaviors in mice and further support an anxiolytic role for endogenous cannabinoid signaling. These results suggest that pharmacological modulation of this system could represent a new approach to the treatment of anxiety-related psychiatric disorders.

Marijuana is widely used throughout the world for recreational and therapeutic purposes. A common reason given for continued marijuana use in certain populations is reduction in anxiety and relaxation; however, adverse reactions, including heightened anxiety and panic, are common and widely cited reasons for discontinuation of marijuana use. The adverse effects of marijuana are more pronounced during novel or stressful environmental conditions, after consumption of large doses of cannabis, and in naive users…”

Role of endocannabinoid system in the ventral hippocampus of rats in the modulation of anxiety-like behaviours.

“The effects of unilateral intra-ventral hippocampus injection of URB597, a fatty acid amid hydrolase inhibitor, and AM251, a selective CB(1) receptor antagonist, on anxiety-related behaviours using elevated plus-maze test of anxiety were evaluated in the present study. Possible involvement of GABAergic system in those effects of URB597 was also evaluated. Injection of URB597 at the doses of 0.01, 0.1 and 1 microg/rat showed significant anxiogenic-like effects at 0.1 and 1 microg/rat. However, intra-ventral hippocampus injection of AM251 at the doses of 0.001, 0.01 and 0.1 microg/rat did not produce any significant effect in the elevated plus-maze. The ineffective doses of selective GABA(A) receptor antagonist, bicuculline (2 microg/rat) and selective GABA(B) receptor antagonist, phaclofen (1 microg/rat) on anxiety-related behaviours were also injected with URB597 (0.1 microg/rat). The present data showed that neither bicuculline nor phaclofen affected the anxiogenic-like effects of URB597. The results showed that injection of URB597 into the ventral hippocampus may be anxiogenic and GABAergic system may not be involved in its anxiogenic-like effects.”

An Endocannabinoid Signaling System Modulates Anxiety-like Behavior in Male Syrian Hamsters

“An endocannabinoid signaling system has not been identified in hamsters.

We examined the existence of an endocannabinioid signaling system in Syrian hamsters using neuroanatomical, biochemical and behavioral pharmacological approaches.

The distribution of cannabinoid receptors was mapped and membrane fatty-acid amide hydrolase (FAAH) activity and levels of fatty-acid amides were measured in hamster brain. The impact of cannabinoid CB1 receptor blockade and inhibition of FAAH was evaluated in the elevated plus maze, rota-rod test and models of unconditioned and conditioned social defeat.


A characteristic heterogeneous distribution of cannabinoid receptors was detected in hamster brain..

Endocannabinoids engage functional CB1 receptors in hamster brain to suppress anxiety-like behavior and undergo enzymatic hydrolysis catalyzed by FAAH. Our results further suggest that neither unconditioned nor conditioned social defeat in the Syrian hamster is dependent upon cannabinoid CB1 receptor activation.”

Effects of cannabinoids on the anxiety-like response in mice.

“Several pieces of anatomical, biochemical and pharmacological evidence indicate that the endocannabinoid system via CB1 receptors is implicated in the control of emotional behavior. However, previous studies have reported unclear and contradictory results concerning the role of cannabinoids in anxiety. The aim of the present study was to examine the influence of the cannabinoid agonist WIN 55,212-2, the CB1 antagonist AM 281, the inhibitor of anandamide hydrolysis AACOCF3  and the inhibitor of anandamide transporter AM404 on the anxiety-like response in mice in the light/dark box test…

  These results support the hypothesis that the endocannabinoid system is involved in the regulation of anxiety-like behavior, and also suggest that the inhibitors of anandamide hydrolysis might be potential anxiolytic drugs.”

Facilitation of endocannabinoid effects in the ventral hippocampus modulates anxiety-like behaviors depending on previous stress experience.

“Although several pieces of evidence indicate that the endocannabinoid system modulates anxiety-like behaviors and stress adaptation, few studies have investigated the brain sites of these effects. The ventral hippocampus (VHC) has been related to anxiety behaviors and has a high expression of cannabinoid-1 (CB1) receptors. Moreover, endocannabinoid signaling in the hippocampus is proposed to regulate stress adaptation. In the present study we investigated the role of previous stressful experience on the effects of AM404, an anandamide uptake inhibitor, microinjected into the VHC of rats submitted to the elevated plus maze (EPM), a widely used animal model of anxiety…

These results suggest that facilitation of endocannabinoid system neurotransmission in the ventral hippocampus modulates anxiety-like behaviors and that this effect depends on previous stress experience.”

Anxiolytic Effects in Mice of a Dual Blocker of Fatty Acid Amide Hydrolase and Transient Receptor Potential Vanilloid Type-1 Channels

“The endocannabinoid-inactivating enzyme, fatty acid amide hydrolase (FAAH), and the transient receptor potential vanilloid type-1 (TRPV1) channel are new targets for the development of anxiolytic drugs…

 Simultaneous ‘indirect’ activation of CB1 receptors following FAAH inhibition, and antagonism at TRPV1 receptors might represent a new therapeutic strategy against anxiety.”

The endogenous cannabinoid anandamide has effects on motivation and anxiety that are revealed by fatty acid amide hydrolase (FAAH) inhibition

“Converging evidence suggests that the endocannabinoid system is an important constituent of neuronal substrates involved in brain reward processes and emotional responses to stress.. It is known that the endocannabinoid system plays a modulatory role in emotional states such as anxiety and fear. Several studies utilizing rodent models of anxiety or depression showed that FAAH inhibition produced anxiolytic-like effects and anti-depressant-like effects…