Wiley, Journal of Neuroendocrinology, 12(25), p. 1273-1279
DOI: 10.1111/jne.12104
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Periodic ovulation in rats mice and hamsters is the result of a surge in LH that depends on circadian gating signals emerging from the master circadian clock within the suprachiasmatic nucleus (SCN) and rising ovarian oestrogen levels. These two signals converge into the anteroventral periventricular nucleus (AVPV) and lead to the release of kisspeptin which is responsible for surges of GnRH and in turn of LH release. How the AVPV integrates circadian and reproductive signals remains unclear. Here we show that the female rat AVPV itself shows circadian oscillations in the expression of the clock genes PER1 and BMAL1 which lie at the core circadian clockwork of mammals. In ovariectomized (OVX) females treated with estradiol (E2 ) these oscillations are in synchrony with the AVPV rhythmic expression of the KISS1 gene and the gene that codes for the arginine-vasopressin (AVP) receptor AVPr1a. Whereas clock gene oscillations are independent of oestrogen levels circadian expression of Kiss1 and Avpr1a (also referred to as V1a) mRNA are respectively blunted and absent in ovariectomized animals without E2 replacement. Because AVP is believed to be a critical SCN transmitter to gate the LH surge our data suggest that a there is a circadian oscillator located in the AVPV and that such a putative oscillator could time in an oestrogen dependent manner the sensitivity to circadian signals emerging from the SCN and the release of kisspeptin This article is protected by copyright. All rights reserved.