Melatonin, The Pineal Gland and Circadian Rhythms
Abstract
Amniote circadian organization derives from the interaction circadian oscillator and photoreceptors located in the hypothalamic suprachiasmatic nuclei (SCN), the pineal gland and the eyes. In mammals, circadian organization is dominated by the SCN which serve as 'master pacemakers' in the control of a wide array of behavioral and physiological rhythms including locomotion, sleep/wake, thermoregulation, cardiovascular function and many endocrine processes. Among the rhythms under SCN control in mammals is the circadian synthesis and secretion of the pineal hormone melatonin which relies on a multi-synaptic pathway via the sympathetic nervous system to maintain and entrain rhythmicity in this hormone. Several studies have indicated that pineal melatonin feeds back on SCN rhythmicity to modulate circadian patterns of activity and other processes. However, the nature and system-level significance of this feed-back is unknown. Recently published work indicates that while pinealectomy does not affect rat circadian rhythms in LD or DD, wheel-running activity rhythms are severely disrupted in LL. These data suggest that either (1) pineal feed back regulates the light sensitivity of the SCN and/or (2) it affects coupling among circadian oscillators within the SCN or between the SCN and its output. Research in our laboratory is currently addressing each of these hypotheses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 30, 1992
- Accession Number
- ADA264099
Entities
People
- Vincent M. Cassone
Organizations
- Texas A&M University