"Unravelling the impacts of climatic heat events on cardiovascular health in animal models"

Climate change has led to an increase in high ambient temperatures, causing extreme heat events worldwide. According to the World Meteorological Organization (WMO), July 2023 marked a historic milestone as the Earth reached its hottest recorded temperature, precisely hitting the critical threshold of 1.5 °C set by the Paris Agreement. This distressing development led to a stark warning from the United Nations, signaling the dawn of what they call "an era of global boiling". The increasing global temperatures can result in high heat stress which leads to various physiological and biochemical alterations in the human body. Given that cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality globally, heat events exacerbate this public health issue. While clinical and in-vitro studies have suggested a range of pathophysiological and biochemical mechanisms underlying the body's response to heat stress, the complex nature of organ-system level interactions makes precise investigation challenging. To address this knowledge gap effectively, the use of animal models exposed to acute or chronic heat stress can be invaluable. These models can closely replicate the multifaceted effects observed in humans during heat stress conditions. Despite extensive independent reviews, limited focus has been shed on the high heat-induced cardiovascular complications and their mechanisms, particularly utilizing animal models. Therefore, in this comprehensive review, we highlight the crucial biomarkers altered during heat stress, contributing significantly to various CVDs. We explore potential mechanisms underlying heat-induced cardiovascular dysfunction and damage, delving into various animal models. While traditional rodent models are commonly employed, we also examine less conventional models, including ruminants, broilers, canines, and primates. Furthermore, we delve into various potential therapeutic approaches and preventive measures. These insights hold significant promise for the development of more effective clinical interventions against the effects of heat stress on the human cardiovascular system.

Validating a human model for anxiety using startle potentiated by cue and context: the effects of alprazolam, pregabalin, and diphenhydramine

BACKGROUND

Fear-potentiated startle has been suggested as a translational model for evaluating efficacy of anxiolytic compounds in humans. Several known anxiolytic compounds have been tested as well as several putative anxiolytics. Because results of these studies have been equivocal, the aim of the present study was to examine another pharmacological permutation of the human potentiated startle model by comparing two anxiolytic agents to a non-anxiolytic sedative and placebo.

METHODS

Twenty healthy volunteers participated in a double-blind, placebo-controlled, cross-over study with four sessions in which they received single doses of the anxiolytics alprazolam (1 mg) and pregabalin (200 mg), as well as diphenhydramine (50 mg) as a non-anxiolytic sedative control and placebo. The design included a cued shock condition that presumably evokes fear and an unpredictable shock context condition presumably evoking anxiety.

RESULTS

None of the treatments reliably reduced either fear- or anxiety-potentiated startle. Alprazolam and diphenhydramine reduced overall baseline startle. Alprazolam was found to only affect contextual anxiety in a statistical significant way after two subjects who failed to show a contextual anxiety effect in the placebo condition were excluded from the analysis. Pregabalin did not significantly affect any of the physiological measures.

DISCUSSION

The negative findings from this study are discussed in terms of methodological differences between designs and in variability of startle both between and within study participants.

CONCLUSION

Even though fear-potentiated startle may be used to translate preclinical evidence to human populations, methodological issues still hamper the application of this model to early screening of putative anxiolytic drugs.