Light deprivation improves melatonin related suppression of hippocampal plasticity

Talaei, S.A. and Sheibani, V. and Salami, M. (2010) Light deprivation improves melatonin related suppression of hippocampal plasticity. Hippocampus, 20 (3). pp. 447-455.

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In early postnatal life, sensory inputs deeply influence development as well as function of the brain. Plasticity of synaptic transmission including its experimentally induced form, long-term potentiation (LTP), is affected by sensory deprivation in neocortex. This study is devoted to assess if dark rearing and a dark phase synthesized hormone melatonin influence LTP in the hippocampus, an area of brain involved in learning and memory. In vivo experiments were carried out on two groups of 45-days-old male Wistar rats kept in standard 12-h light/dark condition light reared (LR) tested during the light phase or in complete darkness dark reared (DR) since birth to testing. Each group, in turn, was divided to two, vehicle- and melatonin-treated, groups. Stimulating the Schaffer collaterals of CA3 area of hippocampus extracellular postsynaptic potentials (EPSPs) were recorded in the CA1 area. Having the stable baseline responses to the test pulses, the hippocampus was perfused by either vehicle or 2 lg melatonin and EPSPs were recorded for 30 min. Then, for induction of LTP, the tetanus was applied to the Schaffer collaterals and the field potentials were pooled for 120-min post-tetanus. The light deprivation resulted in a significant augmentation in the amplitude of baseline responses. Also, we observed a melatonin-induced increase in amplitude of the baseline recordings in either LR or DR animals. Tetanic stimulation elicited LTP of EPSPs in both LR and DR groups, robustly in the former where it lasted for about 90 min. Generally, melatonin inhibited the production of LTP in the two groups especially in the LR animals leading to a noticeable depression. We concluded that higher level of neuronal activity in the DR rats gives rise to a lower level of LTP. Weaker effect of melatonin on blocking the potentiation of post-tetanus EPSPs in the DR rats may be the result of a desensitization of melatonin receptors due to chronically increased levels of this hormone in the visually deprived rats. © 2009 Wiley-Liss, Inc.

Item Type: Article
Additional Information: cited By 21
Uncontrolled Keywords: melatonin, animal behavior; animal experiment; article; controlled study; darkness; depression; excitatory postsynaptic potential; hippocampus; in vivo study; light; light dark cycle; long term potentiation; male; nerve cell plasticity; nonhuman; priority journal; rat; rearing, Action Potentials; Animals; Axons; CA1 Region, Hippocampal; CA3 Region, Hippocampal; Circadian Rhythm; Darkness; Electric Stimulation; Excitatory Postsynaptic Potentials; Hippocampus; Light; Long-Term Potentiation; Male; Melatonin; Neural Inhibition; Neural Pathways; Neuronal Plasticity; Photic Stimulation; Rats; Rats, Wistar
Subjects: Medicine
Divisions: Faculty of Medicine > Basic Sciences > Department of physiology
Depositing User: editor . 2
Date Deposited: 26 Feb 2017 06:19
Last Modified: 28 Feb 2017 15:28

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