title: Photic entrainment of circadian rhythms in rodents.
abstract: Photic entrainment of circadian rhythms occurs as a consequence of daily, light-induced adjustments in the phase and period of the suprachiasmatic nuclei (SCN) circadian clock. Photic information is acquired by a unique population of retinal photoreceptors, processed by a distinct subset of retinal ganglion cells, and conveyed to the SCN through the retinohypothalamic tract (RHT). RHT neurotransmission is mediated by the release of the excitatory amino acid glutamate and appears to require the activation of both NMDA- and non-NMDA-type glutamate receptors, the expression of immediate early genes (IEGs), and the synthesis and release of nitric oxide. In addition, serotonin appears to regulate the response of the SCN circadian clock to light through postsynaptic 5-HT1A or 5-ht7 receptors, as well as presynaptic 5-HT1B heteroreceptors on RHT terminals.
authors.affiliation: Biological Rhythms and Integrative Neuroscience Institute, Air Force Research Laboratory, Brooks AFB, Texas, USA. rmea@alcft.brooks.af.mil
authors.forename: M A
authors.initials: MA
authors.lastname: Rea
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D018698:Glutamic Acid / Q000502:physiology; D007031:Hypothalamus / Q000502:physiology; D008027:Light; D010786:Photoreceptor Cells / Q000502:physiology; D017470:Receptors, Glutamate / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D011985:Receptors, Serotonin / Q000502:physiology; D012160:Retina / Q000502:physiology; D012377:Rodentia / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000502:physiology* / Q000528:radiation effects; D009435:Synaptic Transmission
chemical_list: D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D011985:Receptors, Serotonin; D018698:Glutamic Acid