Fast feedback inhibitory transmission among circadian clocks keeps network in tune

LIA FRENKEL; NARA I MURARO; M. FERNANDA CERIANI

Mar del Plata

Congreso; XXX Congreso Anual de la Sociedad Argentina de Investigación en Neurociencias; 2015

Sociedad Argentina de Investigación en Neurociencias

Thecircadian network in the adult Drosophilabrain relies on 150 neurons organized in clusters. One of them, the smalllateral neurons ventral (sLNvs), is a major pacemaker since it defines thetemporal organization of locomotor activity. Nevertheless, all independentyet interconnected oscillators operate coherently to provideflexibility to the network. The small and large LNvs release the PDF neuropeptide.While the relevance of PDF in the synchronization of the circadian network iswell established, the role of fast neurotransmission has only recently beenaddressed. We showed that LNvs release glycine onto other circadian clustersand postulated that it organizes the firing pattern of clock neurons. Reducingglycine availability within LNvs alters PDF release, and remodeling of the sLNvterminals, suggesting that LNvs are also glycinergic targets. RNAi-baseddownregulation of a glycine receptor subunit reduced the consolidation ofdiurnal activity and increased nocturnal activity, decreasing overallrhythmicity. Moreover, glycine application abrogates firing of both s- andl-LNVs, consistent with an inhibition mediated by a ligand-gated Cl- channel. Furthermore,an antibody for human glycine alpha1 receptor (GlyR) stained both s- and l-LNvsneurons, providing further support to the notion that LNvs express GlyR. Wepropose that glycine is a fast feedback inhibitory signal that modulates theoutput of the sLNvs, and thus provides coherence to the circadian network.