Specific Aim 1 will be to provide a preliminary demonstration that acute administration of the first-in-class, FDA-approved insomnia agent, suvorexant, a mixed ORX1/2 receptor antagonist, will block 35% CO2-induced panic symptoms in PD patients, via amelioration of central ORX neuronal hyperactivity (as reflected in blunted plasma ORX responses to CO2 challenge).