Melatonin synthesis in chicken retina: effect of kainic acid-induced lesions on the diurnal rhythm and D2-dopamine receptor-mediated regulation of serotonin N-acetyltransferase activity

Neurosci Lett. 1992 Jan 20;135(1):71-4. doi: 10.1016/0304-3940(92)90138-w.


The effect of kainic acid (KA)-induced lesions of retinal neurons on regulation of serotonin N-acetyltransferase (NAT) activity in chicken retina was investigated. Although NAT activity was higher in KA-lesioned retinas than in controls, the pattern of diurnal variation of enzyme activity throughout 36 h of constant darkness was similar for both tissues. Quinpirole, a selective D2-dopamine receptor agonist, inhibited the nocturnal increase of NAT activity in both control and KA-treated retinas. Quinpirole was significantly more potent in KA-treated retinas than in controls; the ED50 value for quinpirole was 3 times lower in KA-treated retinas than in control tissues. KA treatment markedly reduced retinal levels of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC). We conclude that: (1) NAT activity in retina is localized primarily to KA-insensitive cells, presumably photoreceptors; (2) KA-sensitive inner retinal neurons are not essential to the maintenance of the circadian rhythm of NAT activity; and (3) KA-induced lesions of retinal cells result in supersensitivity of D2-dopamine receptors regulating NAT activity in a mechanism that involves adaptive changes following a decline in retinal dopamine neurotransmission.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Arylamine N-Acetyltransferase / metabolism*
  • Chickens
  • Circadian Rhythm / drug effects*
  • Darkness
  • Dopamine Agents / pharmacology
  • Ergolines / pharmacology
  • Homeostasis / drug effects
  • Kainic Acid / pharmacology*
  • Light
  • Male
  • Melatonin / metabolism*
  • Quinpirole
  • Receptors, Dopamine / drug effects
  • Receptors, Dopamine / physiology*
  • Receptors, Dopamine D2
  • Reference Values
  • Retina / drug effects
  • Retina / enzymology*


  • Dopamine Agents
  • Ergolines
  • Receptors, Dopamine
  • Receptors, Dopamine D2
  • Quinpirole
  • Arylamine N-Acetyltransferase
  • Melatonin
  • Kainic Acid