Korean J Ophthalmol.  2005 Sep;19(3):219-226. 10.3341/kjo.2005.19.3.219.

Neuroprotective Effect of Citicoline on Retinal Cell Damage Induced by Kainic Acid in Rats

• Han YS
• Chung IY
• Park JM
• Yu JM

• KMID: 754428
• DOI: http://doi.org/10.3341/kjo.2005.19.3.219

Abstract

PURPOSE
To examine whether citicoline has a neuroprotective effect on kainic acid (KA) -induced retinal damage. METHODS: KA (6 nmol) was injected into the vitreous of rat eyes. Citicoline (500mg/kg, i.p.) was administered to the rats once before and twice a day after KA-injection for 3- and 7-day intervals. The neuroprotective effects of citicoline were estimated by measuring the thickness of the various retinal layers using hematoxylin-eosin (H and E) staining. In addition, immunohistochemistry was conducted to elucidate the expression of endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS). RESULTS: Morphometric analysis of retinal damage in KA-injected eyes showed significant cell loss in the inner nuclear layer (INL) and inner plexiform layer (IPL) of the retinas at 3 and 7 days after KA injection, but not in the outer nuclear layer (ONL). At 3 days after citicoline treatment, no significant changes were detected in the retinal thickness and immunoreactivities of eNOS and nNOS. The immunoreactivities of eNOS and nNOS increased in the retina at 7 days after the KA injection. However, prolonged treatment for 7 days significantly attenuated the immunoreactivities and the reduction of thickness. CONCLUSIONS: The results indicate that citicoline has a neuroprotective effect on KA-induced neurotoxicity in the retina.

Keyword

Citicoline; Kainic acid; Neuroprotective effect; NOS

MeSH Terms

Retina/*drug effects/*pathology
Rats, Sprague-Dawley
Rats
Neurotoxins/*pharmacology
Neuroprotective Agents/*pharmacology
Male
Kainic Acid/*pharmacology
Cytidine Diphosphate Choline/*pharmacology
Animals

Figure

• 

  Fig. 1 Representative photomicrographs of transverse sections in rat retina at 3 days after KA injection using H-E staining. In control retina, five, well organized retinal layers are seen (A). The thickness of the retina is markedly reduced due to loss of IPL and INL in the KA-injected group (B) but is more conserved in the citicoline treated KA-injected group than in the KA-injected group (C). ONL: outer nuclear layer; OPL: outer plexiform layer; INL: inner nuclear layer; IPL: inner plexiform layer; GCL: ganglion cell layer; CTL: control rats; KA: kainic acid-injected group; Citicoline: citicoline treated group with KA injection.

• 

  Fig. 2 Representative photomicrographs of transverse sections in rat retina at 7 days after KA injection using H-E staining. In control retina, five, well organized retinal layers are seen (A). The thickness of the retina is markedly reduced due to loss of IPL and INL in the KA-injected group (B) but is well conserved in the citicoline treated KA-injected group (C).

• 

  Fig. 3 (A) Qualification of changes in the thickness of the inner nuclear layer (INL) in each group at 3 and 7 days after KA injection. The difference shows statistical significance between the citicoline treated and only KA-injected groups at 7 days. (B) Qualification of changes in the thickness of the inner plexiform layer (IPL) in each group at 3 and 7 days after KA injection. The difference also shows statistical significance between the citicoline treated and only KA-injected groups at 7 days (*P<0.05). KA: kainic acid-injected group; Citicoline: citicoline-treated group with KA injection.

• 

  Fig. 4 Photomicrographs of rat retina of the 3 groups using eNOS immunohistochemistry at 3 days after KA injection. In the citicolinetreated rats (C), immunoreactivity was a little weakened than in the kainic acid-injected group (B). Control group was (A).

• 

  Fig. 5 Photomicrographs of rat retina of the 3 groups using eNOS immunohistochemistry at 7 days after KA injection. In the citicolinetreated rats (C), immunoreactivity was more weakened than in the kainic acid-injected group (B). Control group was (A).

• 

  Fig. 6 Graphs showing the mean percentage value of the intensity of the eNOS (endothelial nitric oxide synthase) immunoreactivity (mean%±SD) in the retinas of the 3 groups. KA-induced retinal damage increased eNOS immunoreactivity in the retina. In the citicoline-treated retina, eNOS immunoreactivity were significantly decreased at 7 days (*P<0.05).

• 

  Fig. 7 Photomicrographs of rat retina of the 3 groups using nNOS immunohistochemistry at 3 days after KA injection. In the citicoline-treated rats (C), immunoreactive cells were a little decreased than in the kainic acid-injected group (B). Control group was (A).

• 

  Fig. 8 Photomicrographs of rat retina of the 3 groups using nNOS immunohistochemistry at 7 days after KA injection. In the citicolinetreated rats (C), immunoreactive cells were more decreased than in the kainic acid-injected group (B). Control group was (A).

• 

  Fig. 9 Graphs showing the mean percentage value of the number of nNOS immunoreactive cells (mean%±SD) in the retinas of the 3 groups. KA-induced retinal damage increased nNOS immunoreactive cells in the retina. In the citicoline-treated retina, nNOS immunoreactive cells significantly decreased at 7 days (*P<0.05).

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