Journal Article

Opioid-receptor antagonism increases pain and decreases pleasure in obese and non-obese individuals

Price, Rebecca C., Schweinhardt, Petra, Backman, Steven B., Christou, Nicolas V., Stone, Laura

2016

Overview

Rationale Endogenous opioids inhibit nociceptive processing and promote the experience of pleasure. It has been proposed that pain and pleasure lie at opposite ends of an affective spectrum, but the relationship between pain and pleasure and the role of opioids in mediating this relationship has not been tested. Objectives Here, we used obese individuals as a model of a dysfunctional opioid system to assess the role of the endogenous opioid peptide, beta-endorphin, on pain and pleasure sensitivity. Methods Obese (10M/10F) and age- and gender-matched non-obese (10M/10F) controls were included in the study. Pain sensitivity using threshold, tolerance, and subjective rating assessments and perceived sweet pleasantness using sucrose solutions were assessed in two testing sessions with placebo or the opioid antagonist, naltrexone (0.7 mg/kg body weight). Beta-endorphin levels were assessed in both sessions. Results and conclusions Despite having higher levels of baseline beta-endorphin and altered beta-endorphin-reactivity to naltrexone, obese individuals reported a similar increase in pain and decrease in pleasantness following naltrexone compared to non-obese individuals. Beta-endorphin levels did not correlate with pain or pleasantness in either group, but naltrexone-induced changes in pain and pleasantness were mildly correlated. Moreover, naltrexone-induced changes in pain were related to depression scores, while naltrexone-induced changes in sweet pleasantness were related to anxiety scores, indicating that pain and pleasantness are related, but influenced by different processes.

• Publisher: Springer Berlin Heidelberg,Springer,Springer Nature B.V
• Subject: Adult / Antagonists (Biochemistry) / Anxiety / beta-Endorphin - metabolism / Biomedical and Life Sciences / Biomedicine / Case-Control Studies / Diagnosis / Female / Health aspects / Humans / Male / Mental depression / Naltrexone - pharmacology / Narcotic Antagonists - pharmacology / Neurosciences / Obesity / Obesity - physiopathology / Opioid Peptides - pharmacology / Original Investigation / Pain / Pain Threshold - drug effects / Pharmacology/Toxicology / Pleasure / Pleasure - drug effects / Psychiatry / Psychological aspects / Psychopharmacology / Sensory Thresholds - drug effects