Circadian variations of human flexion reflex

Giorgio Sandrini, Enrico Alfonsi, Giorgio Bono, Fabio Facchinetti, Lorenza Montalbetti, Giuseppe Nappi

Research output: Contribution to journalArticlepeer-review


We investigated 8 healthy male volunteers, evaluating RII and RIII thresholds every 6 h starting from noon, for a 24-h period. Both reflex responses exhibited a circadian rhythmicity: the lowest values were found in the early morning (9.1 ± 3.0 and 13.1 ± 4.4 mA, respectively), while the highest values were observed at midnight (13.1 ± 3.5 and 18.5 ± 5.3 mA). Also mean cosinor analysis indicated the existence of a significant rhythm with acrophase at 20:12 for RII and 22:29 for RIII. In 4 subjects, β-endorphin plasma (β-EP) level was tested during the day. No correlation was observed between circadian changes of β-EP and RIII threshold. Other factors are likely to be involved in the circadian variation of nociceptive flexion reflex in man.

Original languageEnglish
Pages (from-to)403-410
Number of pages8
Issue number3
Publication statusPublished - 1986

ASJC Scopus subject areas

  • Clinical Neurology
  • Psychiatry and Mental health
  • Neuroscience(all)
  • Neurology
  • Pharmacology
  • Clinical Psychology


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