How does the circadian clock send timing information to the brain?

Semin Cell Dev Biol. 2001 Aug;12(4):329-41. doi: 10.1006/scdb.2001.0260.


This paper discusses circadian output in terms of the signaling mechanisms used by circadian pacemaker neurons. In mammals, the suprachiasmatic nucleus houses a clock controlling several rhythmic events. This nucleus contains one or more pacemaker circuits, and exhibits diversity in transmitter content and in axonal projections. In Drosophila, a comparable circadian clock is located among period -expressing neurons, a sub-set of which (called LN-vs) express the neuropeptide PDF. Genetic experiments indicate LN-vs are the primary pacemakers neurons controlling daily locomotion and that PDF is the principal circadian transmitter. Further definition of pacemaker properties in several model systems will provide a useful basis with which to describe circadian output mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Biological Clocks / genetics
  • Biological Clocks / physiology
  • Brain / physiology*
  • Circadian Rhythm*
  • Drosophila / genetics
  • Drosophila / physiology
  • Drosophila Proteins*
  • Gene Expression
  • Insect Proteins / genetics
  • Insect Proteins / metabolism
  • Mammals
  • Neurons / physiology
  • Neuropeptides / genetics
  • Neuropeptides / metabolism
  • Signal Transduction*
  • Suprachiasmatic Nucleus / physiology*
  • Vasopressins / genetics
  • Vasopressins / physiology


  • Drosophila Proteins
  • Insect Proteins
  • Neuropeptides
  • pdf protein, Drosophila
  • Vasopressins