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

• Published in: Sleep (New York, N.Y.) N.Y.), 2017-12, Vol.40 (12)
• Main Authors: Song, Qian, Feng, Ge, Zhang, Jiaxing, Xia, Xuechun, Ji, Min, Lv, Lei, Ping, Yong
• Format: Article
• Language: English
• Subjects: Animals; Animals, Genetically Modified; Calcium Signaling - drug effects; Calcium Signaling - physiology; Cells, Cultured; Circadian Clocks - physiology; Circadian rhythm; Circadian Rhythm - drug effects; Circadian Rhythm - physiology; Darkness; Drosophila; Drosophila Proteins - physiology; Insects; Magnesium - pharmacology; Magnesium - physiology; Motor Activity - drug effects; Motor Activity - physiology; Mutation - physiology; Neurons - drug effects; Neurons - physiology; Photoperiod; Receptors, N-Methyl-D-Aspartate - physiology; Rest - physiology
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsx166

Abstract Study Objectives 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 were 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 rhythms and we propose that Mg2+ block functions to suppress CaM-stimulated PDE1c activation at resting potential, thus regulating Ca2+ and cyclic AMP oscillations in circadian and sleep circuits.