Photic regulation of c-fos gene expression in the suprachiasmatic nucleus and the circadian rhythm of photosensitivity in the mink.
The relationship between the photic stimulation of the c-fos gene product in cells of the suprachiasmatic nuclei and the photoperiodic control of testicular activity were examined in mink. Mink were kept in a short photoperiod (control, LD4:20), or in 'asymmetric skeleton photoperiods' (groups A and B). The light period for groups A and B was divided into two fractions (3 h 30 min and 30 min); the shorter fraction occurred in the night, 4 h (group A) or 8 h (group B) after the end of the main light period. There was no photic activation of the proto-oncogene c-fos on the control or group A, and 4 weeks on this photoperiodic treatment produced marked testicular development. In contrast, in group B, c-fos mRNA was induced 30 min after the end of the secondary photofraction, was maximal 30 min later and then decreased. Fos-like immunoreactivity was detected 2 h after the end of the secondary photofraction, with activity peaking 1 h later. The animals of this group remained sexually quiescent. These results suggest that photo-induction of the proto-oncogene c-fos is implicated in the gonadal inhibition induced in this species when the light period, extends into the photosensitive phase of the circadian rhythm of photosensitivity.
Boissin-Agasse
L
L
Laboratoire de Neurobiologie endocrinologique, URA 1197 au CNRS, Université Montpellier II, France.
Blanchard
J M
JM
Escot
C
C
Fuminier
F
F
Roch
G
G
Boissin
J
J
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D015870:Gene Expression / Q000235:genetics*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008907:Mink; D010775:Photic Stimulation; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger