PHOTOPERIODIC EXPOSURE AND TIME OF DAY MODULATE THE EXPRESSION OF ARGININE-VASOPRESSIN MESSENGER-RNA AND VASOACTIVE-INTESTINAL-PEPTIDE MESSENGER-RNA IN THE SUPRACHIASMATIC NUCLEI OF SIBERIAN HAMSTERS
Mj. Duncan et al., PHOTOPERIODIC EXPOSURE AND TIME OF DAY MODULATE THE EXPRESSION OF ARGININE-VASOPRESSIN MESSENGER-RNA AND VASOACTIVE-INTESTINAL-PEPTIDE MESSENGER-RNA IN THE SUPRACHIASMATIC NUCLEI OF SIBERIAN HAMSTERS, Molecular brain research, 32(2), 1995, pp. 181-186
In hamsters, changes in ambient photoperiod lead to alterations in the
circadian rhythm of pineal melatonin secretion and subsequent changes
in reproductive function. The present study examined whether photoper
iod also alters 24-h rhythms in neuropeptide mRNA levels in the SCN of
Siberian hamsters. In situ hybridization and quantitative autoradiogr
aphy were used to assess messenger RNA levels for vasopressin (AVP) an
d vasoactive intestinal peptide (VIP) in the SCN of hamsters sacrifice
d at six times of day following exposure to long (16 h light/day) or s
hort (10 h light/day) photoperiod for 2 weeks. Both AVP mRNA and VIP m
RNA in the SCN were significantly affected by time of day and photoper
iodic exposure. The 24-h profiles of AVP mRNA and VIP mRNA showed diff
erent relationships to the light:dark cycle, suggesting that these pro
files are differentially regulated. In general, short photoperiod tend
ed to suppress AVP mRNA and VIP mRNA in the SCN; this effect on AVP mR
NA was significant at two times of day. These results complement and e
xtend previous findings of 24-h h profiles in neuropeptide mRNA expres
sion in the rat SCN by showing that these 24-h profiles are also chara
cteristic of the Siberian hamster SCN and that they can be modulated b
y photoperiod.