[11C]yohimbine + clonidine

[11C]yohimbine + clonidine is a research-grade combination used in positron emission tomography (PET) imaging studies, specifically those conducted by Hospices Civils de Lyon. The combination consists of [11C]yohimbine, a radiolabeled small molecule that acts as an antagonist for alpha-2 adrenergic receptors, and clonidine, a well-characterized alpha-2 adrenergic receptor agonist. In this experimental setup, [11C]yohimbine serves as the imaging tracer to visualize receptor distribution in the brain, while clonidine is administered to displace the tracer from the receptors. This pharmacological challenge allows researchers to quantify receptor occupancy and validate the kinetic modeling of the tracer, facilitating the study of the alpha-2 adrenergic system in humans.