Effects of intravenous caffeine administered to healthy males during sleep

Pharmacological challenge paradigms have been useful for elucidating the phenomenology and neurobiology of panic attacks. A drawback of the pharmacological challenge method is that individual differences in baseline arousal and outcome expectancy can lead to different subjective and physiological drug responses. One method for eliminating differences in baseline arousal and expectancy is to perform pharmacological challenges during non-rapid eye movement (non-REM) sleep. In the present study, fourteen healthy male volunteers received caffeine (5 mg/kg) and placebo (normal saline) during non-REM sleep on two successive nights, in a single-blind manner. Caffeine, compared to placebo, was associated with increased arousal, sleep disruption, and elevations in adrenocorticotropic hormone (ACTH) and cortisol. In one subject, caffeine infusion during sleep induced a panic attack. These findings indicate that caffeine leads to increased arousal and hypothalamic-pituitary-adrenal axis (HPA) axis activation in the absence of high baseline anxiety and expectancy bias. Further, they suggest that similar techniques can be employed in patient populations to elucidate the neurobiology of sleep panic attacks.