Developmental Effects of Melatonin on Synaptic Plasticity of Hippocampal CA۱ Neurons in Visual Deprived Rats

Background & Aims: Change in visual experience impairs circadian rhythms. In this study, The effects of visual deprivation during critical period of brain development and melatonin intake on synaptic plasticity of hippocampal CA۱ neurons were evaluated. Methods: This experimental study was done on male rats kept in standard ۱۲ hour light/dark condition (Light Reared-LR) or in complete darkness (Dark Reared-DR). Each group, was divided into ۳ sub groups of ۲, ۴ and ۶ week old rats (n=۱۶). Excitatory post synaptic field potentials were recorded from dendrite of CA۱ area neurons. Then, half of animals in each group received melatonin via ICV and field potentials recording was repeated. Finally, using tetanic stimulation, Long-term potentiation (LTP) was induced. Results: The amplitude of basic responses of the LR animals decreased with age incaease (P<۰.۰۱). Visual deprivation and also melatonin increased the amplitude of basic responses of the DR group (P<۰.۰۱), and inhibited LTP induction in CA۱ circuits. In comparison to the LR group, melatonin injection had less destructive effect on the LTP induction in the DR group (P<۰.۰۰۱). Conclusion: Visual deprivation during critical period of brain development increases basic responses of rat’s CA۱ neurons and inhibits LTP induction in these neurons, time dependently. Also, the visual deprivation opposes the destructive effects of melatonin on LTP induction in CA۱ neurons in a time-dependent manner.

کلیدواژه ها:

Neuronal Plasticity ، Hippocampus ، Critical Period ، visual perception ، Melatonin ، Rat