Psilocybin Administration With 5-HT1a Blockade

Inclusion criteria: * 21 - 60 years old * Must give written or electronic informed consent * Must have at least a high-school level of education or equivalent (e.g. GED) and are fluent in English * Must be healthy and psychologically stable as determined by screening for medical and psychiatric problems via a personal interview, a medical questionnaire, a physical examination, an electrocardiogram (ECG), and routine medical blood and urinalysis laboratory tests * Must agree not to take any as needed (PRN) medications on the mornings of drug sessions * Must agree not to take sildenafil (Viagra®), tadalafil, or similar medications within 72 hours of each drug administration. * Must agree to refrain from using all psychoactive substances within 24 hours or 5 elimination half-lives (whichever is greater) before psilocybin administration. Caffeine is the exception. * Must have a negative urine toxicology report on the same day as drug dosing. * Who are female and of child-bearing potential and are sexually active, must agree to use highly effective means of birth control (i.e. implants, injectables, combined oral contraceptives, progestin-containing intrauterine device (IUD) or vasectomized partner) for the duration of this study. * Who are male and sexually active, must agree to use contraception and refrain from sperm donation within 90 days of completing dosing sessions. Effective methods of contraception are barrier, hormonal, and sterilization methods. Exclusion Criteria: …