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J Neuroendocrinol. 2010 Sep;22(9):1032-9. doi: 10.1111/j.1365-2826.2010.02045.x. Epub 2010 Jun 24.

Evidence for suprachiasmatic vasopressin neurones innervating kisspeptin neurones in the rostral periventricular area of the mouse brain: regulation by oestrogen.

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  • 1Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.

Abstract

In rodents, a circadian signal from the suprachiasmatic nucleus (SCN) is essential for the pro-oestrous surge of gonadotrophin-releasing hormone (GnRH), which, in turn, induces luteinising hormone (LH) surge and ovulation. We hypothesised that kisspeptin (KP) neurones in the anteroventral periventricular and periventricular preoptic nuclei (AVPV/PeN) form part of the communication pathway between the SCN and GnRH neurones. In anterograde track tracing studies, we first identified vasopressin (VP)-containing axons of SCN origin in apposition to KP-immunoreactive (IR) neurones. Studies to quantify this input relied on the observation that VP-synthesising neurones in the SCN differ from other VP systems in their lack of galanin expression. In ovariectomised mice, 30.79 +/- 1.63% of KP-IR perikarya and proximal dendrites within the AVPV/PeN received galanin-negative VP-IR varicosities. Oestrogen-treatment significantly increased the number of KP-IR neurones, with their percentage apposed by galanin-negative VP-IR varicosities (46.95 +/- 1.88%) and the number of VP-IR appositions on individual KP-IR neurones. At the ultrastructural level, the VP-IR terminals formed symmetric synapses with KP-IR neurones, which was in accordance with the morphology of inhibitory synapses established by SCN neurones. By contrast to VP, vasoactive intestinal polypeptide (VIP), which is synthesised by a distinct subset of SCN neurones, occurred only rarely in axons apposed to KP-IR neurones. Altogether, our results are consistent with the hypothesis that KP neurones located in the mouse AVPV/PeN receive circadian information from the SCN via a vasopressinergic monosynaptic pathway, which is enhanced by oestrogen.

PMID:
20584108
[PubMed - indexed for MEDLINE]
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