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Titolo:
Diurnal rhythms of tryptophan hydroxylase activity in Xenopus laevis retina: opposing phases in photoreceptors and inner retinal neurons
Autore:
Valenciano, AI; Alonso-Gomez, AL; Iuvone, PM;
Indirizzi:
Emory Univ, Dept Pharmacol, Atlanta, GA 30322 USA Emory Univ Atlanta GA USA 30322 iv, Dept Pharmacol, Atlanta, GA 30322 USA
Titolo Testata:
NEUROREPORT
fascicolo: 10, volume: 10, anno: 1999,
pagine: 2131 - 2135
SICI:
0959-4965(19990713)10:10<2131:DROTHA>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
SEROTONIN N-ACETYLTRANSFERASE; CHICKEN RETINA; MELATONIN SYNTHESIS; KAINIC ACID; CIRCADIAN CLOCK; PINEAL-GLAND; EXPRESSION; DESTRUCTION; CELLS;
Keywords:
amacrine cells; diurnal rhythm; melatonin; retina; photoreceptor cells; serotonin; tryptophan hydroxylase;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
25
Recensione:
Indirizzi per estratti:
Indirizzo: Iuvone, PM Emory Univ, Dept Pharmacol, 1510 Clifton Rd, Atlanta, GA 30322 USA Emory Univ 1510 Clifton Rd Atlanta GA USA 30322 a, GA 30322 USA
Citazione:
A.I. Valenciano et al., "Diurnal rhythms of tryptophan hydroxylase activity in Xenopus laevis retina: opposing phases in photoreceptors and inner retinal neurons", NEUROREPORT, 10(10), 1999, pp. 2131-2135

Abstract

TRYPTOPHAN hydroxylase (TPH) is the first enzyme in the biosynthetic pathways of melatonin in photoreceptor cells and of serotonin in amacrine cells. To assess the regulation of TPH activity in photoreceptor cells, we pretreated retinas with kainic acid. The neurotoxin selectively killed inner retinal neurons while sparing photoreceptors. TPH activity in both control and kainate-treated retinas undergoes a day-night rhythm. The rhythms in both preparations fit sinusoidal functions. However, the rhythm in intact retinaspeaks at midday while that in kainate-lesioned retinas does so at midnight. The daily rhythm of tryptophan hydroxylase activity in photoreceptors parallels that of melatonin release. Comparing the mean level of activity in rhythms of intact and lesioned retinas, we calculate that the TPH activity in photoreceptors represents 24% of the total activity. Therefore, the TPH activity measured in intact retinas reflects mainly the enzymatic activity in serotonergic neurons, masking that from photoreceptors. In contrast, the levels and diurnal variation of TPH mRNA did not differ in intact and kainate-lesioned retinas indicating that measurements of TPH mRNA content reflect primarily that in photoreceptor cells. Thus, TPH mRNA levels and enzyme activity are differentially regulated in amacrine neurons and photoreceptor cells. This differential regulation markedly impacts the patterns of daily rhythms observed in the intact retina. NeuroReport 10:2131-2135. (C) 1999 Lippincott Williams & Wilkins.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/09/20 alle ore 07:36:37