Sensory experience differentially underlies developmental alterations of LTP in CA1 area and dentate gyrus.

Postnatal development of the brain relies on genetic codes and sensory inputs. The hippocampus, a well-known area of the brain involved in learning and memory, receives indirect sensory signals through the entorhinal cortex. Stimulating perforant path (PP) excitatory postsynaptic potentials (EPSPs) were recorded in dentate gyrus (DG) and CA1 area of hippocampus of the light (LR) and dark (DR) reared rats at 2 (2W), 6 (6W) and 10 weeks (10W) of postnatal age. Then, the PP was tetanized to induce LTP in both sites of recording. We found a developmental decrease in the amplitude of baseline EPSPs in either DG or CA1 area in the LR rats; opposite was the case in their DR counterparts. Potentiation level in both the CA1 and DG was lower in the DR compared to LR animals. Also, the magnitude of LTP was site-dependent where the degree of LTP was considerably higher in the CA1 compared to the DG in either LR or DR rats. We concluded that: (a) visual signals are necessary for setting the basic activity of hippocampus to mature status, (b) visual deprivation negatively influences NMDA receptor-dependent hippocampal plasticity, (c) the CA1 and DG similarly respond to the sensory deprivation and (d) generally, LTP is weaker in the DG; irrelevant to degree of visual inputs to brain.