A visual circuit uses complementary mechanisms to support transient and sustained pupil constriction

William Thomas Keenan, Alan C. Rupp, Rachel A. Ross, Preethi Somasundaram, Suja Hiriyanna, Zhijian Wu, Tudor C. Badea, Phyllis R. Robinson, Bradford B. Lowell, Samer S. Hattar

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Rapid and stable control of pupil size in response to light is critical for vision, but the neural coding mechanisms remain unclear. Here, we investigated the neural basis of pupil control by monitoring pupil size across time while manipulating each photoreceptor input or neurotransmitter output of intrinsically photosensitive retinal ganglion cells (ipRGCs), a critical relay in the control of pupil size. We show that transient and sustained pupil responses are mediated by distinct photoreceptors and neurotransmitters. Transient responses utilize input from rod photoreceptors and output by the classical neurotransmitter glutamate, but adapt within minutes. In contrast, sustained responses are dominated by non-conventional signaling mechanisms: melanopsin phototransduction in ipRGCs and output by the neuropeptide PACAP, which provide stable pupil maintenance across the day. These results highlight a temporal switch in the coding mechanisms of a neural circuit to support proper behavioral dynamics.

Original languageEnglish (US)
Article numbere15392
Issue numberSeptember2016
StatePublished - Sep 26 2016
Externally publishedYes

ASJC Scopus subject areas

  • General Neuroscience
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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