Evidence that kisspeptin neurons in the AVPV form part of a bisynaptic pathway connecting suprachiasmatic vasopressin neurons with preoptic GnRH cells
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1
Institute of Experimental Medicine, Hungary
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2
Pázmány Péter Catholic University, Department of Neuroscience, Faculty of Health,Medicine and Life Sciences, Hungary
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3
King’s College London, United Kingdom
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4
Univ Tours, INRA, France
Gonadotropin releasing hormone (GnRH) secretion is under circadian regulation in rodents, but the mechanisms underlying this are poorly understood. Findings of our previous studies suggest that vasopressin (VP) neurons in the suprachiasmatic nucleus (SCN) convey signals to GnRH neurons via the anteroventral periventricular nucleus (AVPV). The AVPV contains kisspeptin (KP) neurons, which have been implicated in oestrogen’s positive feedback on GnRH release. Our studies have used confocal- and electronmicroscopy to test the hypotheses that direct contacts are made by VP-immunoreactive (IR) processes from the SCN on AVPV KP neurons and by KP-IR processes on GnRH neurons. Unlike the VP neurons in the supraoptic and paraventricular nuclei and in the bed nucleus of the stria terminalis and medial amygdala, those in the SCN are characterised by absence of galanin expression. Triple-label immunohistochemistry for VP, galanin and KP was carried out on hypothalamic sections from ovariectomised mice treated with estradiol benzoate. Confocal microscopy analysis indicated that nearly half of the KP-IR neurons in the AVPV show somatic or dendritic appositions from VP-IR varicosities lacking galanin-immunoreactivity; at the ultra-structural level, type II symmetric synapses were observed. KP-IR terminals were seen on GnRH perikarya and dendrites; these were not labelled for Neurokinin-B, markers of the KP fibers with arcuate nucleus origin. At the ultrastructural level KP-GnRH contacts displayed type I asymmetric synapses. The present results provide confocal and ultra-structural evidence which is consistent with the hypothesis that KP-IR neurons in the AVPV act as intermediaries between VP neurons in the SCN and GnRH neurons.
Conference:
12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009.
Presentation Type:
Poster Presentation
Topic:
Homeostatic regulatory mechanisms
Citation:
Kalló
I,
Vida
B,
Deli
L,
Kalamatianos
T,
Hrabovszky
E,
Caraty
A,
Liposits
Z and
Clive
CW
(2009). Evidence that kisspeptin neurons in the AVPV form part of a bisynaptic pathway connecting suprachiasmatic vasopressin neurons with preoptic GnRH cells.
Front. Syst. Neurosci.
Conference Abstract:
12th Meeting of the Hungarian Neuroscience Society.
doi: 10.3389/conf.neuro.01.2009.04.014
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Received:
25 Feb 2009;
Published Online:
25 Feb 2009.
*
Correspondence:
Imre Kalló, Institute of Experimental Medicine, Budapest, Hungary, kallo@koki.hu