title: Mice deficient of glutamatergic signaling from intrinsically photosensitive retinal ganglion cells exhibit abnormal circadian photoentrainment.
abstract: Several aspects of behavior and physiology, such as sleep and wakefulness, blood pressure, body temperature, and hormone secretion exhibit daily oscillations known as circadian rhythms. These circadian rhythms are orchestrated by an intrinsic biological clock in the suprachiasmatic nuclei (SCN) of the hypothalamus which is adjusted to the daily environmental cycles of day and night by the process of photoentrainment. In mammals, the neuronal signal for photoentrainment arises from a small subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) that send a direct projection to the SCN. ipRGCs also mediate other non-image-forming (NIF) visual responses such as negative masking of locomotor activity by light, and the pupillary light reflex (PLR) via co-release of neurotransmitters glutamate and pituitary adenylate cyclase-activating peptide (PACAP) from their synaptic terminals. The relative contribution of each neurotransmitter system for the circadian photoentrainment and other NIF visual responses is still unresolved. We investigated the role of glutamatergic neurotransmission for circadian photoentrainment and NIF behaviors by selective ablation of ipRGC glutamatergic synaptic transmission in mice. Mutant mice displayed delayed re-entrainment to a 6 h phase shift (advance or delay) in the light cycle and incomplete photoentrainment in a symmetrical skeleton photoperiod regimen (1 h light pulses between 11 h dark periods). Circadian rhythmicity in constant darkness also was reduced in some mutant mice. Other NIF responses such as the PLR and negative masking responses to light were also partially attenuated. Overall, these results suggest that glutamate from ipRGCs drives circadian photoentrainment and negative masking responses to light.
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: Nicole
authors.initials: N
authors.lastname: Purrier
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: William C
authors.initials: WC
authors.lastname: Engeland
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: Paulo
authors.initials: P
authors.lastname: Kofuji
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000528:radiation effects*; D055786:Gene Knockout Techniques; D018698:Glutamic Acid / Q000378:metabolism*; D008027:Light; D055537:Light Signal Transduction / Q000528:radiation effects*; D018345:Mice, Knockout; D010470:Perceptual Masking / Q000502:physiology; D017440:Photoperiod; D012025:Reflex, Pupillary / Q000528:radiation effects; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000528:radiation effects*; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism
chemical_list: D050599:Vesicular Glutamate Transport Protein 2; D018698:Glutamic Acid