Distinct Panicogenic Activity of Sodium Lactate and Cholecystokinin Tetrapeptide in Patients with Panic Disorder

Comparison of Sodium Lactate Infusion and Carbon Dioxide Inhalation Panic Provocation Tests: A Meta-analysis

BACKGROUND

Sodium lactate (NaL) infusion and carbon dioxide (CO₂) inhalation are proven to provoke acute panic attacks (PAs) in patients with panic disorder (PD). A systematic literature search and meta-analysis were performed to compare the effect sizes of these methods.

METHODS

Odds ratios were calculated for each of the original studies and were pooled using the random-effects model.

RESULTS

Either NaL or CO₂ provocations significantly increased the rates of PAs in individuals with PD compared to those in healthy controls. However, the effect size of NaL infusion (OR=25.13, 95% CI=15.48-40.80) was significantly greater than that of CO₂ inhalation (OR=10.58, 95%CI=7.88-14.21).

CONCLUSION

The evidence for the efficacy of the two panic provocation tests is very strong. Yet, the results support the superiority of NaL infusion over CO₂ inhalation challenge as a panic provocation test. Thus, lactate seems a much stronger stimulus than CO₂ for the brain suffocation detector.

Exposure-induced changes of plasma metabolome and gene expression in patients with panic disorder

BACKGROUND

Anxiety disorders including panic disorder (PD) are the most prevalent psychiatric diseases leading to high disability and burden in the general population. Acute panic attacks are distinctive for PD but also frequent in other anxiety disorders. The neurobiology or specific molecular changes leading to and present during panic attacks are insufficiently known so far.

METHODS

In the present pilot study, we investigated dynamic metabolomic and gene expression changes in peripheral blood of patients with PD (n = 25) during two exposure-induced acute panic attacks.

RESULTS

The results show that the metabolite glyoxylate was dynamically regulated in peripheral blood. Additionally, glyoxylate levels were associated with basal anxiety levels and showed gender-related differences at baseline. As glyoxylate is part of the degradation circuit of cholecystokinin, this suggests that this neuropeptide might be directly involved in exposure-induced panic attacks. Only gene expression changes of very small magnitude were observed in this experimental setting.

CONCLUSIONS

From this first metabolome and gene expression study in exposure-induced acute panic attacks in PD we conclude that metabolites can potentially serve as dynamic markers for different anxiety states. However, these findings have to be replicated in cohorts with greater sample sizes.

Effects of psychosocial and physical stress on lactate and anxiety levels

Both intense physical activity and potent psychosocial stressors increase blood lactate. Raising lactate levels by infusing the chemical can have an anxiogenic effect. Here, we compare the relationship between changes in lactate and anxiety levels resulting from two standardized stressors. We investigated the effects of the Multiple Wingate All-Out Performance Test (WG), a strong physical stressor, and the Trier Social Stress Test (TSST), a well-documented psychosocial stressor, in 32 healthy young men using a crossover design. Before and after each stressor, venous blood was analyzed for lactate levels and the State-Trait-Anxiety Inventory (STAI) was given. Both stressors raised both lactate and anxiety significantly above their baseline levels. While the rise in lactate was much higher for the WG than for the TSST, the rises in anxiety were nearly equal. Individual fitness did not influence the results for lactate or anxiety. No significant relation between lactate and anxiety changes were found. Thus, our results as well as the literature suggest that lactate is an important variable for understanding the impact of sport participation.

Biological and psychological markers of stress in humans: focus on the Trier Social Stress Test

Validated biological and psychological markers of acute stress in humans are an important tool in translational research. The Trier Social Stress Test (TSST), involving public interview and mental arithmetic performance, is among the most popular methods of inducing acute stress in experimental settings, and reliably increases hypothalamic-pituitary-adrenal axis activation. However, although much research has focused on HPA axis activity, the TSST also affects the sympathetic-adrenal-medullary system, the immune system, cardiovascular outputs, gastric function and cognition. We critically assess the utility of different biological and psychological markers, with guidance for future research, and discuss factors which can moderate TSST effects. We outline the effects of the TSST in stress-related disorders, and if these responses can be abrogated by pharmacological and psychological treatments. Modified TSST protocols are discussed, and the TSST is compared to alternative methods of inducing acute stress. Our analysis suggests that multiple readouts are necessary to derive maximum information; this strategy will enhance our understanding of the psychobiology of stress and provide the means to assess novel therapeutic agents.