Hyperalgesia Induced by Naloxone Follows Diurnal Rhythm in Responsivity to Painful Stimuli

Abstract

A diurnal rhythm was observed in the responsiveness of mice to nociceptive stimuli and in the hyperalgesic activity of naloxone. These rhythms may follow a diurnal rhythmicity in the activity of endogenous opioid peptides and may partly account for previous controversy over the direct action of naloxone in opiate-naive animals.