CONICET | Buscador de Institutos y Recursos Humanos

The rotation of our planet generates cyclic environmental conditions to which organisms have adapted by developing an endogenous clock. This allows them to anticipate the daily changes in light and temperature to adjust their physiology and behaviors accordingly. These 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 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. The firing mode of the large-LNvs (lLNvs) follows a circadian pattern, with a high activity bursting mode preponderant during the day and a lower activity tonic mode 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 mechanisms that allow this change in firing mode are not known. Ih (hyperpolarisation-activated cation current) provides a depolarizing current which contributes to resting membrane potential and opposes deviations away from the prevailing membrane potential. In the past, this current has been shown to participate in complex neuronal behaviors such as bursting. Using genetics and pharmacology coupled to whole-cell patch clamp electrophysiology in ex-vivo Drosophila brains, we show here that Ih is indeed involved in the bursting behavior of the lLNvs. We will also show that not only intrinsic, but also synaptic factors, such as Acetylcholine and GABA are contributing to the establishment of the lLNvs firing mode.