eLife Assessment
This valuable study uses technically challenging long-term in vivo recordings and computational modeling to investigate whether hawkmoth olfactory receptor neurons show circadian modulation of spontaneous firing. The study provides solid evidence that ORNs have a circadian pattern of spontaneous firing that is Orco-dependent although Orco transcript abundance does not itself show circadian rhythmicity, and that cAMP can modulate Orco-dependent activity. Together with the computational work, the study proposes the provocative hypothesis that an Orco-centered post-translational feedback loop generates the circadian rhythm of spontaneous firing. Nevertheless, this mechanistic interpretation will require direct testing in future work.