Circadian variations in expression of the trkB receptor in adult rat hippocampus

The expression of brain-derived neurotrophic factor (BDNF) in the central nervous system (CNS) and the expression of its high-affinity trkB receptor on neuron surfaces are known to depend on neuron activity. The expression of BDNF (mRNA and protein) and trkB mRNA shows circadian oscillations in rat...

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Published in:Brain research 2003-12, Vol.994 (1), p.67-72
Main Authors: Dolci, Claudia, Montaruli, Angela, Roveda, Eliana, Barajon, Isabella, Vizzotto, Laura, Grassi Zucconi, Gigliola, Carandente, Franca
Format: Article
Language:English
Subjects:
Animals
Biochemistry and metabolism
Biological and medical sciences
Central nervous system
Circadian Rhythm - physiology
Circadian variations
Fundamental and applied biological sciences. Psychology
Gene Expression Regulation - physiology
Hippocampus
Hippocampus - metabolism
Male
Rat
Rats
Rats, Wistar
Receptor, trkB - analysis
Receptor, trkB - biosynthesis
Receptor, trkB - genetics
RNA, Messenger - biosynthesis
RNA, Messenger - genetics
trkB receptor
Vertebrates: nervous system and sense organs
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Summary:The expression of brain-derived neurotrophic factor (BDNF) in the central nervous system (CNS) and the expression of its high-affinity trkB receptor on neuron surfaces are known to depend on neuron activity. The expression of BDNF (mRNA and protein) and trkB mRNA shows circadian oscillations in rat hippocampal homogenates. We investigated circadian variations in trkB expression in specific areas of the adult rat hippocampal formation by immunohistochemistry. In sets of two experiments performed in the spring, 39 2-month-old male Wistar rats were accustomed to a 12-h light–12-h dark cycle for 2 weeks. Three animals were then sacrificed every 4 h. Forty-micrometer-thick coronal sections of hippocampal formation were obtained and processed for trkB immunohistochemistry. Cell staining intensity was assessed by image analysis of different hippocampal areas on five sections per animal. Circadian rhythmicity was evaluated by the cosinor method. Statistically significant circadian variations in trkB expression were found in dentate gyrus, entorhinal cortex, and the CA3 and hilar regions of the hippocampus, with highest expression during the first half of the dark (activity) period. These findings suggest a relationship between trkB expression and the physiological neuronal activation of wakefulness. TrkB receptor expression in the hippocampal regions studied was continuous and changes were gradual over the 24-h cycle, suggesting that more complex regulatory mechanisms also intervened.
ISSN:0006-8993
1872-6240
DOI:10.1016/j.brainres.2003.09.018