Regulation of vasoactive intestinal polypeptide release in the suprachiasmatic nucleus circadian clock.
Timing of the mammalian circadian clock of the suprachiasmatic nucleus (SCN) is regulated by photic input from the retina. Retinorecipient units entrain rhythmicity of SCN pacemaker cells in part through their release of vasoactive intestinal polypeptide (VIP). The underlying nature of this process is conjectural, however, as in-vivo SCN VIP release has never been measured. Here, SCN microdialysis was used to investigate mechanisms regulating VIP. Hamsters under light-dark cycle of 14:10 exhibited a daily peak in synaptic VIP release near midday. Under constant darkness, this output was arrhythmic. Light and the glutamatergic agonist, N-methyl-D-aspartate, stimulated VIP release at night, whereas the serotonin (1A,7) agonist, (±)8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide, suppressed release at midday. Hence, SCN VIP activity is stimulated by photic input and inhibited by serotonin.
Francl
Jessica M
JM
Department of Biological Sciences, Kent State University, Kent, Ohio 44242, USA.
Kaur
Gagandeep
G
Glass
John David
JD
D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D006224:Cricetinae; D008297:Male; D008647:Mesocricetus; D017551:Microdialysis / Q000379:methods; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010775:Photic Stimulation / Q000379:methods; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
D014660:Vasoactive Intestinal Peptide