Cholinergic Transmission in the Circadian Pacemaker of Drosophila

MILDINER, S; CERIANI MF; FRENKEL, L

Mar del Plata, 27 Septiembre al 1 Octubre 2015.

Congreso; XXX Congreso anual de la SAN; 2015

Sociedad Argentina de Investigaciones en Neurociencias

The central circadian oscillator of Drosophila melanogaster is composed of about 150 neurons organized in clusters defined by their anatomical location. Among them, the lateral ventral neurons (LNvs) are central in the temporal organization of the fly´s daily locomotor activity. The LNv cluster includes two groups of neurons, the large and small LNvs. These neurons release a neuropeptide called Pigment Dispersing Factor. While the relevance of PDF released by the sLNvs in the synchronization of the circadian network is well established, the role of fast neurotransmission is still under debate. LNvs release glycine. This inhibitory signal organizes the coherence of the firing of specific circadian clusters. Notwithstanding, excitatory cholinergic transmission also seems to be implicated. To uncover the role of acetylcholine in the LNvs, we downregulated the expression of the vesicular acetylcholine transporter. We found that the temporal organization of locomotor activity is changed under these conditions. Flies display less consolidated diurnal and increased nocturnal activity. A reduction in the levels of acetylcholine vesicular transporter produces a loss of about 40% in the rhythmicity of the population. We are in the process of defining which group of LNvs is responsible for the behavioral phenotype and also whether reducing acetylcholine availability affects additional sLNv outputs. We postulate that LNvs make use of both excitatory and inhibitory signals in favor of organizing an harmonious firing pattern in the circadian circuit.