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Regulation of tryptophan hydroxylase expression by a retinal circadian oscillator in vitro

, : Regulation of tryptophan hydroxylase expression by a retinal circadian oscillator in vitro. Brain Research 677(2): 283-290

Many aspects of retinal physiology are controlled by a circadian clock including at least two steps in the melatonin synthetic pathway: the activity of the enzyme, N-acetyltransferase (NAT), and mRNA levels of the rate-limiting enzyme tryptophan hydroxylase (TPH). Light and dopamine (through D2-like dopamine receptors) can phase shift the clock, and can also acutely inhibit NAT activity, resulting in suppressed melatonin synthesis. In this paper, we show that eyecups cultured in constant darkness maintain a clock-controlled rhythm in TPH mRNA, with low levels in early day, rising to a peak in early night. Both eyecups and isolated retinas, cultured in light during the day, also exhibit a similar increase in TPH mRNA levels. indicating that this expression is not acutely inhibited by light. Treatment with light or quinpirole (D2 dopamine receptor agonist) in early night, at a time and dose that acutely inhibits NAT activity, does not change levels of TPH mRNA. Addition of eticlopride (D2 dopamine receptor antagonist) during the day, also has no effect on the normal daytime increase in TPH message levels. Therefore, TPH mRNA level is controlled by a circadian clock located within the eye, but acute effects of light or dopamine are not detected.


PMID: 7552254

DOI: 10.1016/0006-8993(95)00166-n

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D.P.epe, V.; Boschet, A.F.ancois; Nixon, S.C.arles, 2002: Comparability of assessments of nutrient emissions to inland waters undertaken within eight European Union Member States. The study aimed to compare ten assessment procedures for nutrient emissions to inland waters arising from diffuse agricultural sources. Eight European Union Member States have independently developed these procedures. They essentially relate emiss...

Bewers J.M.; Miller G.R.J.; Kester D.R.; Warner T.B., 1973: Rapid Changes in the Fluoride to Chlorinity Ratio south of Greenland. Nature(Physical Science (London) 242(122): 142-143

Ross H.M., 1971: Supernatural beliefs and demographic realities in northern malaita solomon islands. Pacific Science Congress Proceedings 1: 257

Seelemann, M.; Pfeffer, A., 1940: Influence of Foot and Mouth Disease on the Course of Bovine Brucellosis. In view of the impressions of certain veterinarians that an outbreak of F. & M. disease tends to be followed by an increased number of cases of abortion, retained placenta, sterility, and mastitis, the authors studied carefully the effects of F. &...

D.L.ise, M.; Harker, M., 1989: Skeletal muscle metabolism: effect of age, obesity, thyroid and nutritional status. Rate of oxygen consumption was estimated in soleus muscle isolated from male and female Balb/c, CBA and NZO mice 5 to 35 weeks old to study the potential role of skeletal muscle metabolism in the estimation of whole body energy balance. Hyperthyro...

Shoeb, S.M.; Basmy, K.; Habib, M.A.; Aidaros, S.M., 1966: Studies of liver biopsies by the transparency and the histopathological techniques for the diagnosis of the bilharzial nature of 96 cases of endemic hepatosplenomegaly. Journal of the Egyptian Medical Association 49(5): 347-355

Schumacher A., 1970: On a fern rich heap of dead rock in southern westphalia olpe area germany. Decheniana 123(1-2)

Malloy, T.B.J.; Romagni, J.; Vincent, L.; Wuenschel, D.D.; Nguyen, D.T.; Bueso, E.; Early, E.A.n; Blanco, R., 2003: Mass spectrometry as a screen for identifying bioactive species in lichen extracts. Abstracts of Papers American Chemical Society 225(1-2): CHED 91

Hurt, R., 2004: Tuberculosis sanatorium regimen in the 1940s: a patient's personal diary. Journal of the Royal Society of Medicine 97(7): 350-353

Ritter E.A., 1905: The gold mining district of Cripple Creek, Colorado. Annales des Mines 10(7): 465-487