NEUROPROTECTIVE EFFECTS OF INTRAMUSCULAR KETAMINE IN RABBIT RETINAS AFTER PARS PLANA VITRECTOMY AND SILICONE OIL INJECTION

Abstract

To investigate potential retinal neuroprotective effects of intramuscular ketamine in rabbits after pars plana vitrectomy (PPV) and intravitreal silicone oil injection (SOI). Twelve New Zealand rabbits (weight, 2.0-2.5 kg) underwent PPV with SOI in the right eye. Postoperatively, six rabbits received a daily intramuscular injection of ketamine for 4 weeks (ketamine-operated eyes), and six rabbits received a daily intramuscular injection of saline (saline-operated eyes). The retina from the left eye of each rabbit served as a control (ketamine-control and saline-control eyes). The animals were euthanized at 4 weeks after surgery. Qualitative and quantitative analyses were performed using the Zeiss Axiophot microscope and KS 400 software. Qualitative analysis using light microscopy demonstrated more extensive edema and cell disorganization in saline-operated retinas than in ketamine-operated, ketamine-control, and saline-control retinas. Quantitatively, the cell densities (cell/mm) in the outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer (GCL) in saline-operated retinas were significantly (P < 0.05) lower than those in these layers in ketamine-operated, ketamine-control, and saline-control retinas. The cell density in the ONL in saline-operated retinas was 52% lower than that in ketamine-operated retinas, 55% lower than that in ketamine-control retinas, and 56% lower than that in saline-control retinas. The cell density in the INL in saline-operated retinas was 44% lower than that in ketamine-operated retinas, 48% lower than that in ketamine-control retinas, and 49% lower than that in saline-control retinas. The cell density in the GCL in saline-operated retinas was 60% lower than that in ketamine-operated retinas, 64% lower than that in ketamine-control retinas, and 64% lower than that in saline-control retinas. PPV with SOI was associated with retinal cell death and disorganization in rabbit eyes. Intramuscular ketamine administration provided protection against these effects.