AII amacrine neurons of the rat retina show diurnal and circadian rhythms of parvalbumin immunoreactivity.
We investigated parvalbumin immunoreactivity (PA-IR) in the retinas of rats maintained on a 12:12 h light:dark cycle, or after being placed in constant darkness for 24-72 h. Retinas were harvested at zeitgeber and circadian times 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 h. PA-IR was found primarily in retinal amacrine cells of the AII subtype. In a light/dark cycle, PA-IR showed a clear rhythm, with a low near zeitgeber time (ZT) 10:00 h and a peak near ZT 18:00 h. The ratio of immunofluorescence intensities at these timepoints was >15-fold. When animals were kept in complete darkness for 1-3 days, the rhythm of PA-IR was still preserved, but was progressively reduced in amplitude. The rhythm of PA-IR inferred from immunohistochemical data was confirmed by Western blots. We conclude that PA-IR in the rat retina shows an underlying circadian rhythm that is enhanced by cyclic light. The regulation may involve translocation of the protein between cell compartments and/or new protein synthesis.
Gábriel
Robert
R
Department of General Zoology and Neurobiology, University of Pécs, 7601 Pécs, u 6, Ifjúság, Hungary. gabriel@ttk.pte.hu
Lesauter
Joseph
J
Bánvölgyi
Tamás
T
Petrovics
György
G
Silver
Rae
R
Witkovsky
Paul
P
D025042:Amacrine Cells / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D008027:Light; D008297:Male; D010320:Parvalbumins / Q000378:metabolism*; D051381:Rats; D012160:Retina / Q000166:cytology / Q000378:metabolism*
D010320:Parvalbumins