Background and purpose: Anxiety is often characterized by an inability to extinguish learned fear responses. Orexins/hypocretins are involved in the modulation of aversive memories, and dysregulation of this system may contribute to the aetiology of anxiety disorders characterized by pathological fear. The mechanisms by which orexins regulate fear remain unknown. Experimental approach: We investigated the role of the endogenous cannabinoid system in the impaired fear extinction induced by orexin-A (OXA) in male mice. Behavioural pharmacology, neurochemical, molecular and genetic approaches were used. Key results: The selective inhibitor of 2-arachidonoylglycerol (2-AG) biosynthesis O7460 abolished the fear extinction deficits induced by OXA. Accordingly, increased 2-AG levels were observed in the amygdala and hippocampus of mice treated with OXA that do not extinguish fear, suggesting that high levels of this endocannabinoid are related to poor extinction. Impairment of fear extinction induced by OXA was associated with increased expression of CB2 cannabinoid receptor (CB2R) in microglial cells of the basolateral amygdala. Consistently, the intra-amygdala infusion of the CB2R antagonist AM630 completely blocked the impaired extinction promoted by OXA. Microglial and CB2R expression depletion in the amygdala with PLX5622 chow also prevented these extinction deficits. Conclusions and implications: We reveal that overactivation of the orexin system leads to impaired fear extinction through 2-AG and amygdalar CB2R. This novel mechanism may pave the way towards novel potential approaches to treat diseases associated with inappropriate retention of fear, such as post-traumatic stress disorder, panic anxiety and phobias.

Background and Purpose: Cocaine addiction causes serious health problems and no effective treatment is available yet. We previously identified a genetic risk variant for cocaine addiction in the PLCB1 gene and found this gene upregulated in postmortem brains of cocaine abusers and in human dopaminergic neuron-like cells after an acute cocaine exposure. Here, we functionally tested the contribution of PLCB1 gene to cocaine addictive properties in mice. Experimental approach: We used heterozygous Plcb1 knockout mice (Plcb1+/-) and characterized their behavioral phenotype. Subsequently, mice were trained for operant conditioning and self-administered cocaine for 10 days. Plcb1+/- mice were assessed for cocaine motivation, followed by 26 days of extinction and finally evaluated for cue-induced reinstatement of cocaine seeking. Gene expression alterations after reinstatement were assessed in medial prefrontal cortex (mPFC) and hippocampus (HPC) by RNAseq. Key Results: Plcb1+/- mice showed normal behavior, although they had increased anxiety and impaired short-term memory. Importantly, after cocaine self-administration and extinction, we found a reduction in the cue-induced reinstatement of cocaine-seeking behavior in Plcb1+/- mice. After reinstatement, we identified transcriptomic alterations in the medial prefrontal cortex of Plcb1+/- mice, mostly related to pathways relevant to addiction like the dopaminergic synapse and long-term potentiation. Conclusions and Implications: To conclude, we found that heterozygous deletion of the Plcb1 gene decreases cue-induced reinstatement of cocaine seeking, pointing at PLCB1 as a possible therapeutic target for preventing relapse and treating cocaine addiction.

AIM: Immune response hyperactivation is critical in the progression of coronavirus disease (COVID-19). We studied the effect of the pre-exposure to disease-modifying antirheumatic drugs (DMARDs) that decrease immunological responses on the incidence of COVID-19 symptoms to explore therapeutic approaches in its early stages. METHODS: Multicentre retrospective cohort study including 2,494 patients with inflammatory diseases recruited from 14 primary care centres in Barcelona (Spain). The primary outcome was the presence of confirmed or highly suspected COVID-19 (hsCOVID-19) symptoms reported during March 2020 at primary care or hospital emergency department. Multivariable Poisson regression models were fitted to estimate hsCOVID-19 symptoms relative risk (RR) adjusted by comorbidities. RESULTS: Biological (RR=0.46, CI95%=0.31-0.67) and synthetic (RR=0.62, CI95%=0.43-0.91) DMARDs used in immunomediated inflammatory diseases diminished the incidence of symptomatic cases of hsCOVID-19. Striking sex differences were revealed. Protective effects of anti-TNFα pre-exposure (RR=0.50, CI95%=0.33-0.75) were higher in women (RR=0.33, CI95%=0.17-0.647), whereas anti-IL6/12/17/23 compounds pre-exposure (RR=0.47, CI95%=0.24-0.92) produced slightly higher protective effects in men (RR=0.44, CI95%=0.15-1.68). Pre-exposure to low glucocorticoid doses also revealed sex differences decreasing the incidence of hsCOVID-19 symptoms predominantly in women (RR=0.72, CI95%=0.42-1.22). A merely protective effect of pre-exposure to chloroquine/hydroxychloroquine (RR 0.76, CI95%=0.36-1.62) was observed. CONCLUSION: We identified specific DMARDs with different immune-depressor mechanisms that decrease hsCOVID-19 symptoms with striking sex differences. These results underline the potential interest of starting clinical trials with anti-TNFα compounds in women to evaluate their efficacy in minimizing disease progression in the early stages of COVID-19.

BACKGROUND AND PURPOSE: Immune response hyperactivation is critical in the progression of coronavirus disease (COVID-19). We studied the effect of the pre-exposure to disease-modifying antirheumatic drugs (DMARDs) that decrease immunological responses on the incidence of COVID-19 symptoms to explore therapeutic approaches in its early stages. EXPERIMENTAL APPROACH: Multicentre retrospective cohort study including 2,494 patients with inflammatory diseases recruited from 14 primary care centres in Barcelona (Spain). The primary outcome was the presence of confirmed or highly suspected COVID-19 (hsCOVID-19) symptoms reported during March 2020 at primary care or hospital emergency department. Multivariable Poisson regression models were fitted to estimate hsCOVID-19 symptoms relative risk (RR) adjusted by comorbidities. KEY RESULTS: Biological (RR=0.46, CI95%=0.31-0.67) and synthetic (RR=0.62, CI95%=0.43-0.91) DMARDs used in immunomediated inflammatory diseases diminished the incidence of symptomatic cases of hsCOVID-19. Striking sex differences were revealed. Protective effects of anti-TNFα pre-exposure (RR=0.50, CI95%=0.33-0.75) were higher in women (RR=0.33, CI95%=0.17-0.647), whereas anti-IL6/12/17/23 compounds pre-exposure (RR=0.47, CI95%=0.24-0.92) produced slightly higher protective effects in men (RR=0.44, CI95%=0.15-1.68). Pre-exposure to low glucocorticoid doses also revealed sex differences decreasing the incidence of hsCOVID-19 symptoms predominantly in women (RR=0.72, CI95%=0.42-1.22). A merely protective effect of pre-exposure to chloroquine/hydroxychloroquine (RR 0.76, CI95%=0.36-1.62) was observed. CONCLUSIONS AND IMPLICATIONS: We identified specific DMARDs with different immune-depressor mechanisms that decrease hsCOVID-19 symptoms with striking sex differences. These results underline the potential interest of starting clinical trials with anti-TNFα compounds in women to evaluate their efficacy in minimizing disease progression in the early stages of COVID-19.