Effects of levodopa on nerve growth factor in visual cortex of kitten / 眼科研究

ABSTRACT

Objective Nerve growth factor (NGF) is thought to be one of regulating factors of cellular function during the visual plasticity period. Levodopa is a neurotransmitter in central nerve system. Its mechanism of improving the visual function in amblyopia is unclear. Present study was to observe the role of levodopa in treating monocular deprived amblyopia and explore the effects of levodopa on the expression of NGF in visual cortex. Methods The animal models of monocular form deprived amblyopia were established in the right eyes of 12 4-week-old domestic cats by suturing the eyelid for 2 weeks and then the left eyes were reverse sutured. The 6 cats from models received 20 mg/kg of levodopa by oral administration. Other 6 normal cats were as normal controls. Pattern VEP (P-VEP) was recorded to check the visual acuity of the cats. The cell number density of NGF expression in visual cortex area 17 was detected and calculated by immunochemistry and expressed as positive number/field. Results The amplitude of P_(100) of P-VEP was significantly declined in monocular deprived eyes compared with fellow eyes and normal eyes in 2 weeks after monocular deprivation (P ＜0. 01) . However, after administration of levodopa, the amplitude of P_(100) recovered to normal 2 weeks later, presenting a insignificant difference between levodopa treating group and normal group (P＞ 0. 05). The latency of P_(100) was followed the same pattern between two groups. The NGF positive cells were decreased in monocular deprived group compared with normal group and levodopa group (80. 23 ± 9. 54 vs 111. 83 ± 7. 49, 80. 23 ± 9. 54 vs 118. 06 ± 12. 37, P ＜ 0. 01), but no significant difference in NGF positive cells was found between normal group and levodopa group (111.83 ±7. 49 vs 118. 06 ± 12. 37, P = 0. 94). Conclusion Levodopa is supposed to accelerate the recovery of visual function in amblyopic cat by enhancing the NGF expression in visual cortex area 17 during the critical period of visual development.