title: Effects of opioid blockade on nociceptive flexion reflex thresholds and nociceptive responding in hypertensive and normotensive individuals.
abstract: Hypertension and risk for hypertension have been associated with reduced pain sensitivity. It has been hypothesised that endogenous opioids contribute to this hypertensive hypoalgesia. The nociceptive flexion reflex can be used as a tool to investigate modulation of nociceptive transmission at spinal level. The current study employed a double-blind placebo-controlled design to compare the effects of naltrexone, an opioid antagonist, and placebo on nociceptive flexion reflex thresholds and nociceptive responding in unmedicated patients with essential hypertension and normotensive individuals. Neither nociceptive flexion reflex thresholds nor nociceptive responding differed between hypertensives and normotensives during placebo or naltrexone. These data provide no support for the hypothesis that essential hypertension is characterised by higher levels of endogenous opioids in the central nervous system and reveal no association between blood pressure status and nociceptive flexion reflex responses.
authors.affiliation: International Centre for Health and Exercise Research, University of Birmingham, Birmingham, B15 2TT, UK. l.edwards@bham.ac.uk
authors.forename: Louisa
authors.initials: L
authors.lastname: Edwards
authors.forename: Christopher
authors.initials: C
authors.lastname: Ring
authors.forename: Christopher R
authors.initials: CR
authors.lastname: France
authors.forename: David
authors.initials: D
authors.lastname: McIntyre
authors.forename: Una
authors.initials: U
authors.lastname: Martin
mesh_terms: D000328:Adult; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009271:Naltrexone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D018847:Opioid Peptides / Q000378:metabolism; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects*; D012016:Reference Values; D012018:Reflex / Q000187:drug effects; D020886:Somatosensory Disorders / Q000150:complications* / Q000378:metabolism
chemical_list: D009292:Narcotic Antagonists; D018847:Opioid Peptides; D009271:Naltrexone