L-type calcium channel antagonist nifedipine reduces neurofilament restitution following traumatic optic nerve injury

Oroxylin A promotes retinal ganglion cell survival in a rat optic nerve crush model

Purpose

To investigate the effect of oroxylin A on the survival of retinal ganglion cells (RGC) and the activation of microglial cells in a rat optic nerve (ON) crush model.

Methods

Oroxylin A (15mg/Kg in 0.2ml phosphate-buffered saline) or phosphate-buffered saline (PBS control) was immediately administered after ON crush once by subcutaneous injection. Rats were euthanized at 2 weeks after the crush injury. The density of RGC was counted by retrograde labeling with FluoroGold and immunostaining of retina flat mounts for Brn3a. Electrophysiological visual function was assessed by flash visual evoked potentials (FVEP). TUNEL assay, immunoblotting analysis of glial fibrillary acidic protein (GFAP), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in the retinas, and immunohistochemistry of GFAP in the retinas and ED1 in the ON were evaluated.

Results

Two weeks after the insult, the oroxylin A-treated group had significantly higher FG labeled cells and Brn3a+ cells suggesting preserved RGC density in the central and mid-peripheral retinas compared with those of the PBS-treated group. FVEP measurements showed a significantly better preserved latency of the P1 wave in the ON-crushed, oroxylin A-treated rats than the ON-crushed, PBS treated rats. TUNEL assays showed fewer TUNEL positive cells in the ON-crushed, oroxylin A-treated rats. The number of ED1 positive cells was reduced at the lesion site of the optic nerve in the ON-crushed, oroxylin A-treated group. Increased GFAP expression in the retina was reduced greatly in ON-crushed, oroxylin A-treated group. Furthermore, administration of oroxylin A significantly attenuated ON crush insult-induced iNOS and COX-2 expression in the retinas.

Conclusions

These results demonstrated that oroxylin A hasss neuroprotective effects on RGC survival with preserved visual function and a decrease in microglial infiltration in the ONs after ON crush injury.

Trans-scleral permeability of Oregon green 488

PURPOSE

The aim of this study was to determine the scleral permeability of a commercially available version of 2',7'-difluorofluorescein (OG) and compare it to that of sodium fluorescein (NaF).

METHODS

Both in vitro and in vivo experiments were performed. For the ex vivo experiment, a Lucite block perfusion chamber with human donor sclera was used. Two hundred microliters (200 microL) of 2.5 mg/ml OG or NaF was placed in the donor chamber. The OG and NaF concentration that diffused across the sclera was measured every 2 h for 24 h by fluorometry, and the fluorescence in the sclera was examined by fluorescent microscopy. In vivo experiments consisted of live rabbits treated with a 0.2-mL subtenon injection of 7.5 mg/ml solution of either OG or NaF in the right eye. Intraocular fluorescence was measured by ocular fluorophotometry.

RESULTS

The scleral permeability coefficient (K(trans)) of OG was 3.93 +/- 1.01 x 10(-7) cm/sec and that of NaF was 4.41 +/- 1.32 x 10(-7) cm/s. Both OG and NaF were visible throughout the sclera after 24 hours. Peak vitreous concentration after subtenon injection in rabbits was 6.48 +/- 2.65 ng/mL of OG at 2 min and 47.15 +/- 13.3 ng/mL of NaF at 10 min.

CONCLUSIONS

OG was able to diffuse across the sclera and thus could be potentially useful as a fluorescent tag for intraocular drug delivery studies. However, its permeability was substantially less than that of NaF.