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Background
Fluoxetine (Flx), a selective serotonin reuptake inhibitor, promotes neurogenesis and synaptogenesis in the adult hippocampus.So it is inferred that Flx plays a role in promoting visual plasticity of visual cortex.However, the associations of oral administration of Flx with remodeling of visual plasticity and its difference from binocular form deprivation (BFD) are unelucidated.
Objective
This study was to investigate the influence of Flx application time to visual plasticity and contrast the mechanism between Flx and BFD in the remodeling of visual cortex plasticity in adult rats by pattern visual evoked potential (PVEP).
Methods
Fifty-six 70-day-old clean Wistar rats were randomized into control group, Flx2 group, Flx4 group, Flx6 group, Flx8 group, BFD group and Flx+ BFD group.Flx was orally used at the dosage of 0.2 mg/ml once per day until 2, 4, 6 and 8 weeks before record of PVEP in the Flx2 group, Flx4 group, Flx6 group, Flx8 group respectively.The eyelids were binocularly sutured for 2 weeks and opened the right eyes 1 week before the record of PVEP to form the BFD and took the normal water in the rats of the BFD group, and the combination of Flx administration and BFD was performed in the Flx+ BFD group.All the left eyes of the rats were sutured for 1 week to form the monocular form deprivation (MFD). No any intervene was conducted in the control group.PVEP was binocularly recorded in the rats to measure the amplitude from N75 wave to P100 wave, and amplitude ratio of left eyes and right eyes (C/I) was calculated.The results between before and after FD were compared to assess the shift of ocular dominance.The use and care of the animals followed ARVO Statement.
Results
The C/I of PVEP was significantly decreased 1 week after FD in comparison with before FD in the Flx4 group, Flx6 group, Flx8 group, BFD group and Flx+ BFD group (t=2.733, P<0.05; t=2.981, P<0.05; t=3.619, P<0.01; t=2.681, P<0.05; t=4.550, P<0.01). The amplitudes of PVEP were significantly lower in the left eyes after FD than those before FD in the Flx4 group ([17.71±2.24]μV vs.[ 31.09±4.13]μV), the Flx6 group ([18.93±2.85]μV vs. [29.59±4.07]μV) and the Flx8 group ([17.94±1.92]μV vs. [28.48±3.09]μV) (t=3.348, 3.278, 4.447, all at P<0.01), while there were significant differences in the amplitudes of PVEP in the right eyes between before and after FD (all at P>0.05). The amplitudes of PVEP were reduced in the left eyes after FD in comparison with before FD in the BFD group and Flx4+ BFD group (t=2.497, P<0.05; t=3.051, P<0.01), however, they were raised in the right eyes in both BFD group and Flx+ BFD group (t=-4.009, P<0.01; t=-4.352, P<0.01).
Conclusions
Both 0.2 mg/ml Flx drinking for over 4 weeks and BFD for 2 weeks can restore visual cortex plasticity in the adult rats.Increasing the dosage time of Flx appears to be incapable to increase the remodeling degree of visual plasticity.Flx and BFD promote visual plasticity primarily by inhibiting the response of FD eyes and BFD can promote the response of non-FD eyes.Flx feeding and BFD play synergy effects in remodeling the visual cortex plasticity in adult rats.