A Causal Role for Voltage-gated Cav1.2 Calcium Channels in Mediating 5G FR1 Effects on Sleep-associated Brain Health in Humans

Inclusion Criteria: For the first part of the study (genotyping and questionnaires): * Age: 20-40 years old. * German and/or English language skills (reading and writing) * Informed Consent as documented by signature For the second and third party of the study: * Completion of the first part of the present study or of the precursor study (BASEC-ID: 2016-02049) * CACNA1C rs7304986 T/C allele-carrier * Male gender * Female gender if using hormonal contraception for the duration of the study (e.g., pill as combination/single preparation, three-month injection, hormonal IUD, hormonal implant, hormonal patch) * Right-handedness * Body Mass Index (BMI): BMI comprised between 17.0 kg/m2 and 26.0 kg/m2 * Moderate alcohol consumption (less than 5 reported alcoholic drinks per week) * Moderate caffeine consumption (less than 3 reported caffeinated beverage or food products per day such as cola, coffee, energy drinks, green and black tea, chocolate) * Informed Consent as documented by signature. Exclusion Criteria: For the second and third party of the study: * Travel with a time difference of more than 2 time zones in the last 30 days before study entry or during the study period * Shift work at night * Extreme chronotype or duration of sleep (5 hours \< reported habitual sleep duration per night \> 10 hours) * Known sleep disorders or diseases * 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 * Use of medications (regularly or during the study period) that, in the opinion of the investigator, may affect study measurements. * Use of illegal drugs * Smoking (or other tobacco use) * Known or suspected non-compliance with the investigators' indications * Inability to follow the procedures of the study, e.g., due to language problems, psychological disorders, dementia, etc. * Severe skin allergies or hypersensitivities * Participation in another clinical trial in the last 30 days prior to inclusion or during the present study * Contraindications to nimodipine, e.g., known hypersensitivity or allergy to nimodipine or any of the excipients * Other cases in which the use of nimodipine is discouraged according to the summary of product characteristics (SPC) * Women who are pregnant or breast feeding * Intention to become pregnant during the course of the study * Lack of safe contraception, defined as: female participants of childbearing potential, not using and not willing to continue using a medically reliable method of contraception for the entire study duration, such as oral, injectable, or implantable contraceptives, or intrauterine contraceptive devices, or who are not using any other method considered sufficiently reliable by the investigator in individual cases (Note: Female participants who are surgically sterilized / hysterectomized or post-menopausal for longer than 2 years are not considered as being of child bearing potential) * Sleep apnea and nocturnal myoclonus index of ≥ 5 per hour of sleep (as assessed during the screening night) * Sleep efficiency \< 80% (as assessed during the screening night) * Other relevant findings in the screening/adaptation night (e.g., indications of sleep disorders), which in the opinion of the investigator may pose a risk for participation or influence the study measurements.