NMDA Receptor-mediated Ca2+ Influx in the Absence of Mg2+ Block Disrupts Rest:activity Rhythms in Drosophila.

NMDA Receptor-mediated Ca2+ Influx in the Absence of Mg2+ Block Disrupts Rest:activity Rhythms in Drosophila.

Sleep. 2017 Oct 03;:

Authors: Song Q, Feng G, Zhang J, Xia X, Ji M, Lv L, Ping Y

Abstract
Introduction: The correlated activation of pre- and postsynaptic neurons is essential for the NMDA receptor-mediated Ca2+ influx by removing Mg2+ from block site and NMDA receptors have been implicated in phase resetting of circadian clocks. So we assessed rest:activity rhythms in Mg2+ block defective animals.
Methods: Using Drosophila locomotor monitoring system, we checked circadian rest:activity rhythms of different mutants under constant darkness (DD) and light:dark (LD) conditions. We recorded NMDA receptor-mediated currents or Ca2+ increase in neurons using patch-clamp and Ca2+ imaging techniques.
Results: We found that Mg2+ block defective mutant flies exhibited completely arrhythmic under DD. To further understand the role of Mg2+ block in daily circadian rest:activity, we observed the mutant files under LD cycles, and we found severely reduced morning anticipation and advanced evening peak compared to control flies. We also used tissue-specific expression of Mg2+ block defective NMDA receptors and demonstrated pigment-dispersing factor receptor (PDFR) expressing circadian neurons were implicated in mediating the circadian rest:activity deficits. Endogenous functional NMDA receptors are expressed in most Drosophila neurons, including in a subgroup of dorsal neurons (DN1s). Subsequently, we determined that the uncorrelated extra Ca2+ influx may act in part through Ca2+/Calmodulin (CaM)-stimulated PDE1c pathway leading to morning behavior phenotypes.
Conclusions: These results demonstrate that Mg2+ block of NMDA receptors at resting potential is essential for the daily circadian rest:activity and we propose that Mg2+ block functions to suppress CaM-stimulated PDE1c activation at resting potential, thus regulating Ca2+ and cAMP oscillations in circadian and sleep circuits.

PMID: 29029290 [PubMed - as supplied by publisher]

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