Spontaneous and light-evoked expression of JunB-like protein in the hamster suprachiasmatic nucleus near subjective dawn.
Some cells in the hamster suprachiasmatic nucleus (SCN) show a circadian rhythm of expression of junB mRNA in constant darkness, while others show junB mRNA only in response to light at night. We found that both the light-induced and spontaneous expressions of junB mRNA are translated into protein in SCN cells. In constant darkness, JunB-like immunoreactivity (lir) appears spontaneously in cells in the dorsal SCN around subjective dawn and persists for at least 4 h into the subjective day. During the subjective night, there is no spontaneous expression, but a light pulse can induce JunB-lir in cells throughout the SCN, and especially in the ventrolateral portion. As a component of AP-1 proteins, JunB may play a role both in mediating circadian responses to photic stimuli and in spontaneous oscillation of elements of the SCN circadian pacemaker.
Guido
M E
ME
Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada.
Goguen
D
D
Robertson
H A
HA
Rusak
B
B
D000704:Analysis of Variance; D000818:Animals; D002940:Circadian Rhythm / Q000528:radiation effects*; D006224:Cricetinae; D003624:Darkness; D007150:Immunohistochemistry; D008027:Light; D008297:Male; D008647:Mesocricetus; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis* / Q000528:radiation effects; D013493:Suprachiasmatic Nucleus / Q000378:metabolism* / Q000528:radiation effects
D016755:Proto-Oncogene Proteins c-jun