Effects of bright light and melatonin on sleep propensity, temperature, and cardiac activity at night

Helen J. Burgess, Tracey Sletten, Natasha Savic, Saul S. Gilbert, Drew Dawson

Research output: Contribution to journalArticleResearchpeer-review

59 Citations (Scopus)

Abstract

Melatonin increases sleepiness, decreases core temperature, and increases peripheral temperature in humans. Melatonin may produce these effects by activating peripheral receptors or altering autonomic activity. The latter hypothesis was investigated in 16 supine subjects. Three conditions were created by using bright light and exogenous melatonin: normal endogenous, suppressed, and pharmacological melatonin levels. Data during wakefulness from 1.5 h before to 2.5 h after each subject's estimated melatonin onset (wake time + 14 h) were analyzed. Respiratory sinus arrhythmia (cardiac parasympathetic activity) and preejection period (cardiac sympathetic activity) did not vary among conditions. Pharmacological melatonin levels significantly decreased systolic blood pressure [5.75 ± 1.65 (SE) mmHg] but did not significantly change heart rate. Suppressed melatonin significantly increased rectal temperature (0.27 ± 0.06°C), decreased foot temperature (1.98 ± 0.70°C), and increased sleep onset latency (5.53 ± 1.87 min). Thus melatonin does not significantly alter cardiac autonomic activity and instead may bind to peripheral receptors in the vasculature and heart. Furthermore, increases in cardiac parasympathetic activity before normal nighttime sleep cannot be attributed to the concomitant increase in endogenous melatonin.

Original languageEnglish
Pages (from-to)1214-1222
Number of pages9
JournalJournal of Applied Physiology
Volume91
Issue number3
Publication statusPublished - 12 Sep 2001
Externally publishedYes

Keywords

  • Heart rate variability
  • Respiratory
  • Sympathetic

Cite this