title: The Dorsal Raphe Nucleus Receives Afferents From Alpha-Like Retinal Ganglion Cells and Intrinsically Photosensitive Retinal Ganglion Cells in the Rat.
abstract: OBJECTIVE
  A retinal projection into the dorsal raphe nucleus (DRN), namely, the retino-raphe projection, exists in many species. The rat is one of several species in which a retino-raphe projection has been described; however, the retinal ganglion cell (RGC) types that contribute to this pathway are unknown.
  
  
  METHODS
  Retrograde tracing via cholera toxin subunit B (CTB) was used to reveal DRN-projecting RGCs in rats, combined with intracellular injection in vitro, melanopsin immunostaining in whole-mounted retinas, and serotonin immunostaining to define the DRN. We modified methods of CTB injection into DRN used previously in order to avoid possible contamination with other retinorecipient regions, particularly the superior colliculus (SC).
  
  
  RESULTS
  The majority of DRN-projecting RGCs showed alpha-like morphology, and some CTB-positive RGCs were colabeled with melanopsin. Approximately 80% of the total population of CTB-labeled DRN-projecting RGCs was alpha-like cells including ON alpha cells and OFF alpha cells; these alpha-like cells were melanopsin immunonegative. Approximately 10% of the remaining DRN-projecting RGCs were melanopsin immunopositive, in which the M1 subtype of intrinsically photosensitive retinal ganglion cell (ipRGC) provided the dominant projection of ipRGCs into DRN, with only few non-M1 ipRGCs involved. The DRN-projecting ipRGCs could be retrogradely labeled following tracer injection into all rostrocaudal aspects of the DRN.
  
  
  CONCLUSIONS
  Both conventional RGCs with alpha-like morphology and melanopsin-expressing ipRGCs project into the rat DRN. Approximately 10% of DRN-projecting RGCs were colabeled with melanopsin, and the majority of these were the M1 subtype of ipRGCs. An ipRGC component of the retino-raphe projection may contribute to a sustained light-mediated modulation of DRN serotonin release.
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of China 2Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of.
authors.forename: Xiaotao
authors.initials: X
authors.lastname: Li
authors.affiliation: GHM Institute of CNS Regeneration, Jinan University, Guangzhou, People's Republic of China.
authors.forename: Chaoran
authors.initials: C
authors.lastname: Ren
authors.affiliation: GHM Institute of CNS Regeneration, Jinan University, Guangzhou, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Huang
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of China 2Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of.
authors.forename: Bin
authors.initials: B
authors.lastname: Lin
authors.affiliation: Department of Anatomy, School of Basic Medical Sciences, Peking University, Beijing, People's Republic of China 8Key Laboratory on Machine Perception (Ministry of Education), Peking University, Beijing, People's Republic of China 9Key Laboratory for Visua.
authors.forename: Mingliang
authors.initials: M
authors.lastname: Pu
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of China 6GHM Institute of CNS Regeneration, Jinan University, Guangzhou, People's Republic of China 10School of Veterinary Medicine.
authors.forename: Gary E
authors.initials: GE
authors.lastname: Pickard
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of China 2Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of.
authors.forename: Kwok-Fai
authors.initials: KF
authors.lastname: So
mesh_terms: D000818:Animals; D065847:Dorsal Raphe Nucleus / Q000166:cytology / Q000378:metabolism*; D008027:Light; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism*; D017299:Rod Opsins / Q000378:metabolism; D013477:Superior Colliculi / Q000166:cytology / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin