Why do animals search for food at specific times of a day? In a study published in Current Biology, a research group led by Prof. LI Yan from the Institute of Biophysics, Chinese Academy of Sciences, has uncovered the neural circuit that links the internal central clock to rhythmic foraging, offering original insights into how circadian timing shapes daily behavior.

Many behaviors of animals exhibit circadian rhythmicity, in particular, foraging shows strong rhythmic patterns. Remarkably, even animals reared under stable temperature and light conditions in the laboratory maintain such rhythmic foraging behavior. However, the neural mechanisms underlying these circadian patterns of behavior await to be elucidated.

The researchers revealed a group of inhibitory projection neurons in the olfactory system, called mlPN3. Behavioral experiments showed that mlPN3 neurons suppress foraging behavior at midday, while this suppression is lifted in the early morning. Functional imaging study revealed that the spontaneous neural activity of mlPN3 neurons exhibits circadian rhythms-lower in the early morning and higher at midday. This fluctuation is driven by a group of circadian neurons, morning cells, which activate dopaminergic neurons PAM-β'2 via pigment-dispersing factor (PDF) neuropeptide in the early morning, thereby inhibiting mlPN3 neurons.

Using the olfactory system as an entry point, this study identified a novel function of inhibitory projection neurons that mediate circadian regulation of foraging behavior -"eating at the right time". The circuit mechanism of disinhibition may underly the circadian regulation of various animal behaviors.

Figure: The neural circuit composed of circadian neurons-dopaminergic neurons-olfactory neurons regulates the rhythmicity of foraging behavior. Right: At midday, high activity of mlPN3 suppresses foraging. Left: In the early morning, these neurons are inhibited, leading to increased foraging activity.

(Image by LI Yan's group)

Article link: https://www.cell.com/current-biology/abstract/S0960-9822(25)01181-9

Contact: LI Yan

Institute of Biophysics, Chinese Academy of Sciences

Beijing 100101, China

E-mail: liyan@ibp.ac.cn

(Reported by Prof. LI Yan's group)