# Photoperiodic Programming of Serotonin Neurons

> **NIH NIH R01** · VANDERBILT UNIVERSITY · 2021 · $66,800

## Abstract

PROJECT SUMMARY
A fundamental question in neuroscience is how environmental signals may have long-lasting effects on neural
circuits and neural function. The circadian clock and circadian photoperiod are associated with mood disorders,
but the neurobiological mechanisms are unknown. Dysregulation of serotonin neurotransmission is implicated
in neurobehavioral disorders, such as depression and anxiety, and alterations in the serotonergic phenotype of
raphe neurons has dramatic effects on affective behaviors in rodents. The serotonergic dorsal raphe nuclei
receive light input from the circadian visual system, as well as polysynaptic input from the biological clock
nuclei, and dorsal raphe serotonin neurons respond acutely to tonic illumination with increased spike rate and
to changes in the circadian light cycle with gene activation. Our laboratory has demonstrated that seasonal
circadian photoperiods (winter –like “short days” vs. summer-like “long days”) can induce enduring changes in
mouse dorsal raphe serotonin neurons - programming their spontaneous neural activity, and altering
depression and anxiety-like behaviors. Here we seek to elucidate the mechanistic basis photoperiodic
programming of serotonin neurons, focusing on electrophysiology, gene regulation and maternal-fetal vs
neonatal developmental windows. We will examine neural mechanisms of photoperiodic programming of
dorsal raphe serotonin neurons using both multi-electrode array and whole cell electrophysiology; altered
gene regulation in serotonin neurons induced by photoperiodic programming using RT-PCR, RNA-seq
gene expression analysis of FACS sorted serotonin neurons and RNA Scope in situ hybridization to determine
the photoperiod programming transcriptome, and the gene network in serotonergic neurons driven by
photoperiodic programming. We will test the hypothesis that the Pet-1 transcription factor is a critical node for
photoperiodic programing and define critical periods for the enduring effects of photoperiod. Successful
completion of these aims will reveal novel mechanisms by which a pervasive environmental signal – the daily
light cycle – can influence the long-term function of brain serotonergic neurons and the behaviors they
mediate.

## Key facts

- **NIH application ID:** 10399697
- **Project number:** 3R01MH108562-05S1
- **Recipient organization:** VANDERBILT UNIVERSITY
- **Principal Investigator:** DOUGLAS G MCMAHON
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $66,800
- **Award type:** 3
- **Project period:** 2016-07-01 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10399697

## Citation

> US National Institutes of Health, RePORTER application 10399697, Photoperiodic Programming of Serotonin Neurons (3R01MH108562-05S1). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10399697. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*