Review Question - QID 214319

A 25-year-old woman presents to the emergency department after she was found somnolent in her room by her roommate. The patient had just come home from a rave and has a history of alcoholism and IV drug abuse. She has attempted suicide multiple times in the past via overdose and wrist cutting. Her temperature is 96.0°F (35.6°C), blood pressure is 90/51 mmHg, pulse is 55/min, respirations are 8/min, and oxygen saturation is 93% on room air. Physical exam is notable for a somnolent patient who arouses to sternal rub. She has bilateral 1 mm pupils that constrict minimally to light. The patient has cold extremities and smells of urine. Which of the following is the mechanism of the most likely etiology of this patient's symptoms?