Neuroprotective Effect Of Etomidate On Axotomized Retinal Ganglion Cells In Adult Rats

Retinal ganglion cells (RGCs) are the output neurons in the retina, extending their axons through the optic nerve (ON) to their targets in the brain. RGC cell bodies are located in the innermost cellular layer of the retina, the ganglion cell layer. The RGCs are central neurons. Diseases of RGCs are common because the ON is involved in a wide variety of pathological states. Preservation of RGCs viability is a major role in clinical practice.Etomidate (ET), a rapidly acting intravenous nonbarbiturate anesthetic, is a frequent agent of choice for induction of rapid sequence intubation in emergency departments. ET has been shown to protect neuronal damage after incomplete ischemia in rats. It has also been shown that ET has neuroprotective effect on the neuronal tissue against the diabetic oxidative damage. The purpose of the present study was to investigate the neuroprotective effect of different dosages of ET on axotomized RGCs in adult rats.The left ONs of adult SD rats were transected at 1mm from the optic disc and the ocular stumps of the transected ON were labeled with FluoroGold. Diferent dosages of ET were injected intraperitoneally together with its solvent propylene glycol (PG) as carrier. Animals were sacrificed at 7 or 14 day time point. Retrogradely labeled surviving RGCs were counted in the flat-mounted retinas and the mean densities of RGC were estimated. ET promoted the RGC densities in a dose-dependent manner at 7 days post-axotomy, when compared with non-treated or PG-treated control animals. Moreover, mean RGC densities in PG-control animals were also higher than those in non-treated control animals when given at a high dosage. However, neither ET nor PG had neuroprotective effect on RGCs survival at 14 days post-axotomy since the mean densities in ET-treated or PG-treated naimals were similar to those in the non-treated animals.In conclusion, ET has a marked neuroprotective effect on the axotomized RGCs at a certain period after ON transection. And high dosage of PG also has a certain surportive effect on ET.