Dopamine regulates melanopsin mRNA expression in intrinsically photosensitive retinal ganglion cells

Eur J Neurosci. 2005 Dec;22(12):3129-36. doi: 10.1111/j.1460-9568.2005.04512.x.


In mammals a subpopulation of retinal ganglion cells are intrinsically photosensitive (ipRGCs), express the photopigment melanopsin, and play an important role in the regulation of the nonimage-forming visual system. We have recently reported that melanopsin mRNA and protein levels in the rat retina are under photic and circadian control. The aim of the present work was to investigate the mechanisms that control melanopsin expression in the rat retina. We discovered that dopamine (DA) is involved in the regulation of melanopsin mRNA, possibly via dopamine D2 receptors that are located on these ipRGCs. Interestingly, we also discovered that pituitary adenylate cyclase-activating peptide (PACAP) mRNA levels are affected by DA. Dopamine synthesis and release in the retina are regulated by the rod and the cone photoreceptors via retinal circuitry; our new data indicate that DA controls melanopsin expression, indicating that classical photoreceptors may modulate the transcription of this new photopigment. Our study also suggests that DA may have an important role in mediating the light signals that are used for circadian entrainment and for other responses that are mediated by the nonimage-forming visual system.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / pharmacology
  • 3,4-Dihydroxyphenylacetic Acid / metabolism
  • Animals
  • Blotting, Western / methods
  • Circadian Rhythm / drug effects
  • Circadian Rhythm / physiology
  • Dopamine / metabolism
  • Dopamine / pharmacology*
  • Dopamine Agonists / pharmacology
  • Dose-Response Relationship, Drug
  • Drug Interactions
  • Excitatory Amino Acid Agonists / pharmacology
  • Gene Expression Regulation / drug effects*
  • Gene Expression Regulation / physiology
  • Immunohistochemistry / methods
  • In Situ Hybridization / methods
  • Kainic Acid / pharmacology
  • Male
  • Quinpirole / pharmacology
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Inbred F344
  • Receptors, Dopamine D2 / genetics
  • Receptors, Dopamine D2 / metabolism
  • Retina / cytology*
  • Retinal Ganglion Cells / drug effects*
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Rod Opsins / genetics
  • Rod Opsins / metabolism*
  • Time Factors


  • Dopamine Agonists
  • Excitatory Amino Acid Agonists
  • RNA, Messenger
  • Receptors, Dopamine D2
  • Rod Opsins
  • melanopsin
  • 3,4-Dihydroxyphenylacetic Acid
  • Quinpirole
  • 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine
  • Kainic Acid
  • Dopamine