Subjective and physiological responses to the 35% carbon dioxide challenge in healthy and non-clinical control populations: a meta-analysis and systematic review

The nature and neurobiology of fear and anxiety: State of the science and opportunities for accelerating discovery

Fear and anxiety play a central role in mammalian life, and there is considerable interest in clarifying their nature, identifying their biological underpinnings, and determining their consequences for health and disease. Here we provide a roundtable discussion on the nature and biological bases of fear- and anxiety-related states, traits, and disorders. The discussants include scientists familiar with a wide variety of populations and a broad spectrum of techniques. The goal of the roundtable was to take stock of the state of the science and provide a roadmap to the next generation of fear and anxiety research. Much of the discussion centered on the key challenges facing the field, the most fruitful avenues for future research, and emerging opportunities for accelerating discovery, with implications for scientists, funders, and other stakeholders. Understanding fear and anxiety is a matter of practical importance. Anxiety disorders are a leading burden on public health and existing treatments are far from curative, underscoring the urgency of developing a deeper understanding of the factors governing threat-related emotions.

Translational evaluation of novel selective orexin-1 receptor antagonist JNJ-61393215 in an experimental model for panic in rodents and humans

Orexin neurons originating in the perifornical and lateral hypothalamic area project to anxiety- and panic-associated neural circuitry, and are highly reactive to anxiogenic stimuli. Preclinical evidence suggests that the orexin system, and particularly the orexin-1 receptor (OX1R), may be involved in the pathophysiology of panic and anxiety. Selective OX1R antagonists thus may constitute a potential new treatment strategy for panic- and anxiety-related disorders. Here, we characterized a novel selective OX1R antagonist, JNJ-61393215, and determined its affinity and potency for human and rat OX1R in vitro. We also evaluated the safety, pharmacokinetic, and pharmacodynamic properties of JNJ-61393215 in first-in-human single- and multiple-ascending dose studies conducted. Finally, the potential anxiolytic effects of JNJ-61393215 were evaluated both in rats and in healthy men using 35% CO₂ inhalation challenge to induce panic symptoms. In the rat CO₂ model of panic anxiety, JNJ-61393215 demonstrated dose-dependent attenuation of CO₂-induced panic-like behavior without altering baseline locomotor or autonomic activity, and had minimal effect on spontaneous sleep. In phase-1 human studies, JNJ-61393215 at 90 mg demonstrated significant reduction (P < 0.02) in CO₂-induced fear and anxiety symptoms that were comparable to those obtained using alprazolam. The most frequently reported adverse events were somnolence and headache, and all events were mild in severity. These results support the safety, tolerability, and anxiolytic effects of JNJ-61393215, and validate CO₂ exposure as a translational cross-species experimental model to evaluate the therapeutic potential of novel anxiolytic drugs.

Variation in the onset of CO2-induced anxiety in female Sprague Dawley rats

Carbon dioxide (CO₂) is commonly used to kill laboratory rats. Rats find CO₂ aversive and aversion varies between individuals, indicating that rats vary in CO₂ sensitivity. Healthy humans experience feelings of anxiety at concentrations similar to those avoided by rats, and these feelings are diminished by the administration of benzodiazepines. Our aim was to assess the effects of the benzodiazepine midazolam on individual thresholds of rat aversion to CO₂. Six female Sprague Dawley rats were repeatedly exposed to CO₂ gradual-fill in approach-avoidance testing. The first three exposures were to a control-treatment followed by three exposures to midazolam (0.375 mg/kg). Within each treatment aversion to CO₂ was not affected by exposure number; however, tolerance increased from an average of 10.7% CO₂ avoided during control sessions, to 15.5% CO₂ avoided when treated with midazolam. These results indicate that rats experience anxiety when exposed to CO₂, and that variation in rat CO₂ sensitivity is driven by individual differences in the onset of these feelings of anxiety. No rat tolerated CO₂ concentrations required to induce loss of consciousness.

The effect of a very low calorie diet on subjective depressive symptoms and anxiety: meta-analysis and systematic review

There are conflicting findings regarding the effect very low calorie diets (VLCDs) have on self-reported depressive symptoms and anxiety levels. Some studies have reported decreased subjective depressive symptoms and anxiety post-diet, whereas other studies have not. Further complicating matters, the protocol for VLCDs vary substantially across studies, which could account for the mixed findings. The primary goal of this meta-analysis and systematic review was to determine the effect VLCDs have on subjective depressive symptoms and anxiety pre- to post-diet. In addition, potential moderators (the presence/absence of behavioral therapy, duration of diet, inclusion/exclusion of low intensity exercise, and amount of weight lost) were examined to assess the effect of procedural deviations across VLCD studies on depressive symptoms and anxiety. A random-effects model was used for the meta-analysis and included nine studies with 16 independent samples. To further explain the results, study rigor was examined in the systematic review, which included 11 studies with 20 independent samples. Depressive symptoms significantly decreased pre- to post-diet when behavioral therapy was implemented during the diet, the duration of the diet was relatively long (8-16 weeks), low intensity exercise was included, and the dieters lost 14.1 kg or more post-diet. However, no difference in depressive symptoms were observed pre- to post-diet when behavioral therapy was not included, the diet was shorter (1-7 weeks), no exercise was implemented and dieters lost <14 kg of weight post-diet. There was no change in anxiety pre- to post-diet. Health care providers involved in supervising VLCDs should consider using a VLCD of at least 8 weeks that includes behavioral therapy and low intensity exercise in order to enhance the potential benefits of VLCDs on depressive symptoms. More research is required to examine the effect of VLCDs on anxiety.