CONICET | Buscador de Institutos y Recursos Humanos

Circadian rhythms have been extensively studied in the fruit fly where many clock genes that interlock through negative feedback loops and generate daily oscillations have been described. Clock genes are highly expressed in approximately 150 clock neurons in the brain, of which a particular subset, the pigment dispersing factor-expressing lateral neurons (LNvs) have been found to play a central role. Behavioral, genetic and molecular approaches have been very successful to unravel circadian biology in Drosophila, however, electrophysiological approaches have lagged way behind. This gap started to fill in the late 2000s when an ex-vivo brain preparation accessible to electrophysiological recordings was developed (Park and Griffith, 2006; Sheeba et al. 2008; Cao and Nitabach, 2008). This preparation permits recording in whole cell patch clamp configuration particularly from the larger type of LNvs (lLNvs). The circadianly more hierarchical small LNvs (sLNvs) have persisted in poor accessibility to electrophysiological analysis. Since then, this preparation has been rather scarcely used, however, several properties of lLNvs have been revealed. An interesting one is the report regarding the firing mode of these neurons following a circadian pattern, with a high activity bursting mode preponderant during the day and a lower activity tonic mode or no spontaneous firing normally found at nighttime. This change in neuronal firing could be crucial to confer time of day information to other neurons by altering the release of neurotransmitters or neuropeptides; however, the molecular mechanisms that allow this change in firing mode are not known. In a quest to find the answer to this, we stumble upon the fact that the firing mode of the lLNvs reflects not only the variation of gene expression controlled by the clock as we hypothesized but depends a great deal on an input from the network.