The Role of the LC-NA System in Experimental Sleep Fragmentation

Following a screening night and a baseline sleep recording, participants undergo three experimental nights in the sleep laboratory. On each of these nights, sleep is intentionally disrupted using auditory stimuli to induce fragmentation. To investigate potential counteracting effects on sleep quality, participants receive either a low dose (64 µg), a high dose (96 µg) of dexmedetomidine (DMTN)-a compound known to reduce norepinephrine levels-or a placebo. All participants experience each condition in a randomized, double-blind, crossover design, with the sequence of administration varying between individuals. Neither the participants nor the study team are aware of the assigned condition on any given night.

In a second part of the study, three additional nights are conducted to assess the pharmacokinetics and pharmacodynamics of dexmedetomidine. During these nights, participants again receive either the low dose (64 µg), high dose (96 µg), or placebo (in randomized order). Blood samples are collected at multiple time points to characterize the compound's pharmacokinetic profile, and additional physiological outcomes are measured to evaluate pharmacodynamic effects.

Inclusion criteria

• Age between 18 - 35 years (inclusive)
• Body-Mass-Index (BMI): 18.5 < BMI < 25
• Non-nicotine user status
• Habitual consumption of 5 or fewer alcoholic beverages / week
• Habitual consumption of 3 or fewer caffeinated beverages / day
• Habitual average sleep duration 7-9 h / night
• Normal or corrected-to-normal vision
• Insomnia severity Index (ISI) Score: ISI < 8
• Ability to understand and speak German language
• Normal hearing ability (applies only to Sleep Study Part)
• Ability and willingness to provide informed consent as documented by dated signature

Exclusion criteria

• Present use of medication that may interfere with sleep or study drugs
• Travel across 3 or more time zones within 3 months of study start
• Habitual napping
• Extreme chronotype, determined by reduced Morningness-Eveningness Questionnaire (rMEQ) score: 8 < rMEQ > 21)
• Shift working within 2 weeks prior to the screening visit
• History of or presence of a trauma- or stressor-related disorder
• Serious acute or chronic neurological, mental, or general medical conditions that, in the opinion of the investigator, may pose a risk to participation or affect study measurements
• History of or presence of a sleep wake disorder
• Use of illicit drugs (positive urinary drug screening)
• Male participants who are not vasectomised for at least 6 months prior to dosing and who are sexually active with a female partner of childbearing potential not willing to use one of the following acceptable contraceptive methods from the first dose and for 3 months after the last dose:

Use of condom and/or hormonal contraceptive (e.g., oral, patch, depot injection, implant, vaginal ring, intrauterine device) or non-hormonal intrauterine device used for at least 4 weeks prior to sexual intercourse for the female partner;

• Male participants (including men who have had a vasectomy) with a pregnant partner not willing to use a condom from the first dose and for 3 months after the last dose.
• Male participants not willing to abstain from sperm donation for 3 months after the last dose
• Females of childbearing potential who are sexually active with a non-sterile male partner (sterile male partners are defined as men vasectomised at least 6 months prior to the first study drug administration) not willing to use one of the following acceptable contraceptive methods throughout the study and for at least 3 months after the last study drug administration:

Simultaneous use of condom and hormonal contraceptive (e.g., oral, patch, depot injection, implant, vaginal ring, intrauterine device) or non-hormonal intrauterine device used for at least 4 weeks prior to sexual intercourse for the female partner;

• Females of non-childbearing potential who are neither: Post-menopausal (status defined as an absence of menses for at least 12 months prior to the first study drug administration); or Surgically sterilized (complete hysterectomy or bilateral oophorectomy at least 3 months prior to the first study drug administration)

• Faints at the sight of blood (applies only for the pharmacokinetic-part of the study)
• Has participated in a study < 30 days or a study such as this (i.e., experimental trauma) at all.