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Abstract #3584 Published in IGR 4-2
Effects of pinealectomy and melatonin on the retrograde degeneration of retinal ganglion cells in a novel model of intraorbital optic nerve transection in mice
Kilic E; Hermann DM; Isenmann S; Bahr MJournal of Pineal Research 2002; 32: 106-111
The effects of pinealectomy and of intraperitoneally administered melatonin on the retrograde degeneration of retinal ganglion cells (RGCs) were examined in a novel model of optic nerve (ON) transection in C57BL/6J mice. RGCs were prelabelled with the fluorescent tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (Di-I), and the ON was cut inside the orbital cavity seven days later. The degree of RGC injury was assessed by counting viable Di-I labelled RGCs in various locations of the retina. In unlesioned control eyes, a mean ganglion cell density of 1891 ± 30/mm2 (mean ± SEM) was determined. The cell density markedly declined at 14 days after axotomy (295 ± 9 cells/mm2; 15.6% of contralateral). Sham-pinealectomy did not influence the density of RGCs at 14 days after ON transection (382 ± 37 cells/mm2). In pinealectomized animals, on the other hand, the RGC number was significantly reduced compared with untreated and sham-pinealectomized animals (91 ± 33 RGCs/mm2). The effect of pinealectomy was reversed after i.p. administration of melatonin (4 mg/kg b.w. bolus followed by continuous infusion of 8 mg/kg b.w./day) (286 ± 27 cells/mm2). On the other hand, in nonpinealectomized animals, i.p. melatonin did not influence the RGC density (344 ± 20 cells/mm2). The present results suggest that endogenous melatonin prevents the delayed degeneration of adult central nervous system (CNS) neurons in vivo, and that exogenous substitution of melatonin may be useful to protect injured neurons against cell death under conditions of melatonin deficiency, e.g., in the aged brain, when melatonin synthesis and secretion have decreased.
Dr. E. Kilic, Department of Neurology, Georg August University, Robert-Koch-Strasse 40, D-37075 Gottingen, Germany. ertugrul.kilic@med.uni-goettingen.de
Classification:
11.8 Neuroprotection (Part of: 11 Medical treatment)
