Evidence of involvement of neurone‐glia/neurone‐neurone communications via gap junctions in synchronised activity of KND KND y neurones

摘要

Pulsatile secretion of gonadotrophin‐releasing hormone (Gn RH )/luteinising hormone is indispensable for the onset of puberty and reproductive activities at adulthood in mammalian species. A cohort of neurones expressing three neuropeptides, namely kisspeptin, encoded by the Kiss1 gene, neurokinin B ( NKB ) and dynorphin A, localised in the hypothalamic arcuate nucleus ( ARC ), so‐called KND y neurones, comprises a putative intrinsic source of the Gn RH pulse generator. Synchronous activity among KND y neurones is considered to be required for pulsatile Gn RH secretion. It has been reported that gap junctions play a key role in synchronising electrical activity in the central nervous system. Thus, we hypothesised that gap junctions are involved in the synchronised activities of KND y neurones, which is induced by NKB ‐ NK 3R signalling. We determined the role of NKB ‐ NK 3R signalling in Ca 2+ oscillation (an indicator of neuronal activities) of KND y neurones and its synchronisation mechanism among KND y neurones. Senktide, a selective agonist for NK 3R, increased the frequency of Ca 2+ oscillations in cultured Kiss1 ‐ GFP cells collected from the mediobasal hypothalamus of the foetal Kiss1 ‐green fluorescent protein ( GFP ) mice. The senktide‐induced Ca 2+ oscillations were synchronised in the Kiss1 ‐ GFP and neighbouring glial cells. Confocal microscopy analysis of these cells, which have shown synchronised Ca 2+ oscillations, revealed close contacts between Kiss1 ‐ GFP cells, as well as between Kiss1 ‐ GFP cells and glial cells. Dye coupling experiments suggest cell‐to‐cell communication through gap junctions between Kiss1 ‐ GFP cells and neighbouring glial cells. Connexin‐26 and ‐37 mRNA were found in isolated ARC Kiss1 cells taken from adult female Kiss1 ‐ GFP transgenic mice. Furthermore, 18β‐glycyrrhetinic acids and mefloquine, which are gap junction inhibitors, attenuated senktide‐induced Ca 2+ oscillations in Kiss1 ‐ GFP cells. Taken together, these results suggest that NKB ‐ NK 3R signalling enhances synchronised activities among neighbouring KND y neurones, and that both neurone‐neurone and neurone‐glia communications via gap junctions possibly contribute to synchronised activities among KND y neurones.