Naltrexone effect on physiological and subjective response to a cold pressor task.

Area of Science:

• Pharmacology
• Neuroscience
• Human Physiology

Background:

• Naltrexone is an opioid receptor antagonist.
• Its effects on physiological stress responses are not fully understood.

Purpose of the Study:

• To investigate the physiological and subjective responses to naltrexone during a cold pressor task.
• To compare the effects of naltrexone with placebo on stress markers.

Main Methods:

• Double-blind, cross-over study design.
• 19 healthy subjects participated.
• Assessed physiological (blood pressure, heart rate, catecholamines, cortisol) and subjective (pain, affect, distress) responses.
• Administered 50 mg naltrexone or placebo 1 hour prior to the cold pressor task.

Main Results:

• Significant increases in plasma epinephrine concentrations were observed 1 hour after naltrexone administration.
• Plasma norepinephrine concentrations showed a significant treatment x period effect.
• No significant differences were found in blood pressure, heart rate, plasma cortisol, or subjective measures.

Conclusions:

• Naltrexone alters catecholamine responses to acute stress.
• Further research is needed to identify responsive subpopulations and long-term safety implications.