Daily profiles of arginine vasopressin mRNA in the suprachiasmatic, supraoptic and paraventricular nuclei of the rat hypothalamus under various photoperiods

Daily rhythm of arginine vasopressin (AVP) mRNA levels in the suprachiasmat ic nucleus (SCN) of rats maintained under a short, LD 8:16 photoperiod diff ered from that of rats maintained under a long, LD 16:8 photoperiod: under the short photoperiod the morning AVP rise occurred significantly later tha n under the long one. Daily profiles of AVP mRNA in the supraoptic and para ventricular nuclei were not rhythmic and AVP mRNA levels under LD 8:16 did not differ from those under LD 16:8. The data indicate that photoperiod aff ects selectively the clock driven AVP gene expression in the SCN. (C) 2000 Elsevier Science B.V. All rights reserved.