BACKGROUND AND OBJECTIVE: Changes in the visual experience during  the critical periods of brain development lead to the dysfunction of  the visual cortex.The visual cortex is a major supplier of sensory input in the mammalian hippocampus. This study aimed to investigate the effects of visual deprivation on the synaptic plasticity of CA1 neurons in this area.

METHODS: This experimental study was conducted on 48 male Wistar rats who had been classified into the two main groups of a 12-12 Light Reared (LR) and Dark Reared (DR) since birth.To perform the experiments, the rats were categorized under 3 subgroups of 2, 4 and 6 weeks of age. Excitatory postsynaptic potentials (EPSP) were recorded for 30 minutes from the dendrites of neurons in the CA1 area. Afterwards, long-term potentiation (LTP) was induced through Tetanic stimulation. Finally, the amplitude of the responses were measured before and after the Tetanic stimulation.

FINDINGS: The amplitude of basic responses in the 2WLR and 6WLR group were 1.28± 0.05 Mv and 1.09 ± 0.03 Mv, respectively (p<0.0001) while the range increased from 1.30 ±0.30 Mv in the 2WDR group to 1.50 ± 0.4 Mv in the 6WDR group (p<0.0001). Upon LTP induction, the highest rise in the amplitude response was observed at the age of 2 weeks in the animals. However, the increasing responses in both groups of LR and DR diminished with age (p<0.0001).

CONCLUSION: Visual deprivation during the critical periods of brain development might lead to an increase in the basal synaptic activity of hippocampal CA1 neurons through an age-related process. Although it does not interrupt the induction of LTP in neurons, it might reduce its intensity and stability.