Circadian activity of the GABAergic system in the golden hamster retina

• Published in: Brain research 2001-09, Vol.912 (2), p.195-202
• Main Authors: Jaliffa, Carolina O, Saenz, Daniel, Resnik, Ernesto, Keller Sarmiento, Marı́a I, Rosenstein, Ruth E
• Format: Article
• Language: English
• Subjects: Animals; Binding Sites - drug effects; Binding Sites - physiology; Biological and medical sciences; Carbon Radioisotopes - pharmacokinetics; Circadian rhythm; Circadian Rhythm - physiology; Cricetinae; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; GABA; gamma-Aminobutyric Acid - metabolism; gamma-Aminobutyric Acid - pharmacokinetics; Glutamate Decarboxylase - metabolism; Glutamic Acid - metabolism; Glutamic Acid - pharmacokinetics; Hamster retina; Male; Mesocricetus - anatomy & histology; Mesocricetus - metabolism; Mesocricetus auratus; Neural Inhibition - physiology; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Photic Stimulation; Radioligand Assay; Retina - cytology; Retina - drug effects; Retina - metabolism; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(01)02736-6

Daily changes in γ-aminobutyric acid (GABA) turnover rate were studied in the golden hamster retina. This parameter showed significant variations throughout the light–dark cycle, with minimal values during the day. Retinal glutamic acid decarboxylase (GAD) activity was higher at midnight than at noon. Moreover, [ 3H]GABA binding significantly varied throughout the 24-h cycle, with maximal values during the day. Saturation studies performed at 12:00 and 24:00 h indicated that the maximal concentration of [ 3H]GABA binding sites ( B max) was significantly higher at noon, whereas the dissociation constant ( K d) remained unchanged. High K +-induced GABA release was significantly higher at midnight than at midday. Daily variations in retinal GABA turnover rate, GABA release, and in its specific binding persisted in golden hamsters exposed to constant darkness. In summary, these results support the idea of a circadian clock-controlled GABAergic activity in the hamster retina.