Changes Of Nitric Oxide Synthase Positive Neurons In The Visual Central System Of Deprived Amblyopia Cats

PrefaceAmblyopia is one of the common eye diseases in children that seriously affects the visual development and results in lifetime decrease of visual acuity if it isnt treated timely and properly. It has been confirmed that visual development holdback due to abnormal visual stimulation is the radical reason of amblyopia. In recent years, studies showed that abnormal visual stimulation could decrease the excitability of neurons in optic pathway in critical period and brought about functional or anatomical neuronic hypogenesis and reconstruction of the connection between nerve cells.Nitric oxide (NO) is an aeriform messenger and generally thought to act as a neurotransmitter in central - and peripheral nervous system. Recently, it has been shown that NO is involved in many celluar process such as visual development , formation, integration and transmission. NO participates in the pre - synaptic and post - synaptic communication and synaptic remodelling as a antidromic messenger. Therefore, NO is responsible for the synaptic plasticity of the visual central system and amblyopia. Nitric oxide synthase ( NOS) is the key enzyme synthesizing NO. It has been showed that the constitutive isoform ( cNOS) in neuron is nicotinamid adenine dinucleotide phosphate - diaphorase ( NADPH -d). So, NADPH - d containing neurons indicate the presence of NOS positive cells.In this experiment, deprived amblyopia model was obtained in young cats by suturing the eye lids of one eye which resulted in abnormal visual experience in critical period. Our study observed the change of nitric oxide synthase (NOS) in the visual central system of normal and monocular deprived kittens and discussed the role of nitric oxide in the etiopathology of amblyopia and provided theexperimental foundation to prevent or treat amblyopia .MethodsTweleve kittens of 3 - 4 weeks old are divided into 2 groups randomly: monocular lid - sutured group and control group. The experimental group with eyelids sutured in one eye is feeded for 12 weeks with the control group in the same condition. Deprived amblyopia model was obtained and certified by P - VEP examination. According to Snider's" A stereotaxic atlas of the cat brain" the lateral geniculate nucleus (LGN) and the area 17 of visual cortex are cut on a freezing microtome into sections after perfusion,fixation and removing brain. Observe the change of NOS in the visual central system of normal and monocular deprived kittens by using nicotinamid adenine dinucleotide phosphate - diaphorase histo-chemical method.Result1. The amplitude of the N1 - P1 was attenuated and latency of the P1 was delayed in deprived eye compared with normal eye or nondeprived eye. The amplitude of the N1 - P1 and latency of the P1 in nondeprived eye werent significantly different with normal eye.2. In normal kittens,NOS positive cells were not seen in any lamina of lateral geniculate nucleus, but NOS positive fibers were discovered. In the nondeprived laminae of LGN of monocular deprived kittens there were strip - shaped distribution, of NOS positive cells, and in the deprived laminae the NOS positive cells were occasionally seen.3. In area 17, NOS positive cells localized predominantly in lays II - IE and lays V - VI. Monocular lid suture had no effect on the distribution pattern and density of NOS positive cells in the visual cortex.