Study design.
Randomized, placebo-controlled crossover study design with pharmaco-fMRI on psilocybin effects in a rat model of alcohol relapse. Two-month-old Wistar rats were used for the experiments and divided into two groups (15 ADE rats and 10 age-matched water drinking controls). The first deprivation period was introduced after twelve weeks of continuous alcohol availability. After a deprivation period (between 2–4 weeks), rats were given access to alcohol again and four more deprivation periods were introduced in a random manner. The duration of drinking and deprivation phases was irregular, i.e., approximately 6 ± 2 weeks and 4 ± 2 weeks, respectively, in order to prevent adaptive behavioral mechanisms. The long-term voluntary alcohol drinking procedure including all deprivation phases lasted for a total of 12 months. Then, all rats were assigned to two scanning sessions in a randomized order: One with psilocybin (1 mg/kg bodyweight, red syringe) and one with saline (2 ml/kg bodyweight, blue syringe). During each pharmaco-fMRI session a structural T2 weighted image was acquired followed by 36 min 30 s of functional resting-state echo-planar imaging (EPI) acquisition under an anesthesia with isoflurane and medetomidine. Each fMRI session was split into a baseline acquisition (minute 0 to 8.5), followed by the injection of psilocybin (minute 10) and the post-injection acquisition (minute 28 to minute 36.5). ADE alcohol deprivation effect rats, Con control rats, EPI echo-planar imaging, fMRI functional magnetic resonance imaging, (Created with 