The same photoreceptor cell separates visual perception and circadian entrainment by using two different neurotransmitters.
A type of light-sensitive cell in the drosophila retina (R8 photoreceptor) transmits two chemical messengers, histamine and acetylcholine, in response to the same light signal. These two molecules act on distinct neurons (L1/TM and AMA) that have different functions: one type creates an image and the other synchronizes biological rhythms with the day–night cycle. Moreover, acetylcholine transmission from R8 photoreceptors requires negative, autocrine — acting on the same receptor — feedback from cotransmitted histamine, which prevents the depletion of acetylcholine by attenuating neurotransmitter release during the light phase.
A single photoreceptor splits perception and entrainment by cotransmission. Na Xiao, Shuang Xu, Ze-Kai Li, Min Tang, Renbo Mao, Tian Yang, Si-Xing Ma, Peng-Hao Wang, Meng-Tong Li, Ajay Sunilkumar, François Rouyer, Li-Hui Cao & Dong-Gen Luo.