Venlafaxine and oxycodone have different effects on spinal and supraspinal activity in man: a somatosensory evoked potential study.
Opioids and antidepressants that inhibit serotonin and norepinephrine reuptake (SNRI) are recognized as analgesics to treat severe and moderate pain, but their mechanisms of action in humans remain unclear. The present study aimed to explore how oxycodone (an opioid) and venlafaxine (an SNRI) modulate spinal and supraspinal sensory processing.



Twenty volunteers were included in a randomized, double-blinded, three-way (placebo, oxycodone, venlafaxine), crossover study. Spinal and full scalp cortical evoked potentials (EPs) to median nerve stimulation were recorded before and after 5 days of treatment. Assessment of the central effects of the three treatments involved: (i) amplitudes and latencies of spinal EPs (spinal level); (ii) amplitudes and latencies of the P14 potential (subcortical level); (iii) amplitudes and latencies of early and late cortical EPs (cortical level); (iv) brain sources underlying early cortical Eps; and (v) brain networks underlying the late cortical EPs.



In the venlafaxine arm, the spinal P11 and the late cortical N60-80 latencies were reduced by 1.8% [95% confidence interval (CI) 1.7%, 1.9%) and 5.7% (95% CI 5.3%, 6.1%), whereas the early cortical P25 amplitude was decreased by 7.1% (95%CI 6.1%, 8.7%). Oxycodone increased the subcortical P14 [+25% (95% CI 22.2%, 28.6%)], early cortical N30 [+12.9% (95% CI 12.5%, 13.2%)] amplitudes and the late cortical N60-80 latency [+2.9% (95% CI 1.9%, 4.0%)]. The brainstem and primary somatosensory cortex source strengths were increased by 66.7% (95% CI 62.5%, 75.0%) and 28.8% (95% CI 27.5%, 29.6%) in the oxycodone arm, whereas the primary somatosensory cortex strength was decreased in the venlafaxine arm by 18.3% (95% CI 12.0%, 28.1%).



Opioids and SNRI drugs exert different central effects. The present study contributed to the much-needed human models of the mechanisms of action of drugs with effects on the central nervous system.
Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark.
Dina
D
Lelic
Division of Neurology, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy.|Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
Massimiliano
M
Valeriani
Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark.|Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Iben W D
IW
Fischer
Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands.
Albert
A
Dahan
Mech-Sense, Department of Gastroenterology and Hepatology, Aalborg University Hospital, Aalborg, Denmark.|Department of Clinical Medicine, Aalborg University, Aalborg, Denmark.
Asbjørn M
AM
Drewes
D000328:Adult; D000701:Analgesics, Opioid / Q000494:pharmacology*; D018687:Antidepressive Agents, Second-Generation / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects; D006801:Humans; D008297:Male; D008475:Median Nerve; D010098:Oxycodone / Q000494:pharmacology*; D000069470:Venlafaxine Hydrochloride / Q000494:pharmacology*; D055815:Young Adult
D000701:Analgesics, Opioid; D018687:Antidepressive Agents, Second-Generation; D000069470:Venlafaxine Hydrochloride; D010098:Oxycodone
SNRI; evoked potential; opioid; source localization