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C Nucci, S Piccirilli, R Nisticò, L Cerulli, G Bagetta; Neuroprotective Effects of Intravitreal Tetanus Neurotoxin (TeNT) Injection in the Lateral Geniculate Nucleus (LGN) of Monocularly Deprived (MD) New-Born Rats . Invest. Ophthalmol. Vis. Sci. 2002;43(13):750.
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Purpose:In new-born rats, MD increases nitric oxide synthesis and causes apoptosis in the controlateral LGN. These events are prevented by antagonists of glutamate receptors (Nucci et al. 2000). Here, we report that intravitreal injection of TeNT, a neurotoxin which blocks neurotransmitter release (Schiavo et al. 2000), prevents MD-induced apoptosis in the LGN. Thus suggesting that MD activates retinal terminals to release excess glutamate in the LGN where it causes apoptosis Methods:We used Long evans new-born rats. At post-natal day 14, the right eyelids were closed for 48h, non deprived rats were used as control (n=6 per group). TeNT (0.1 mg/ml) was injected into the vitreus of the right eye of rats at post-natal day 12, using a Hamilton syringe (2 micronl volume) (n=12). After 48h, that is an approximate time for the toxin to reach the LGN via the optic nerve, the right eyelids of 6 animals were sutured for 48 h. Brain sections were processed for in situ detection of DNA fragmentation (Tunel technique). Morphological characteristics of adjacent sections were assested using Heamatoxylin and eosin(HE)staining. Results:Tunel positive cells were detected in the LGN connected with the deprived eye (3.8+/-0.1 vs 0.44+/-0.2 counted in control). Chromatin marginalization and condensation, typical features of apoptosis, were obsereved in adjacent HE stained sections. Intravitral injection of TeNT, 48h before MD, significantly reduced the number of Tunel positive cell (0.6+/-0.1). Injection of TeNT alone did not induced apoptosis in the LGN (0.44+/-0.1). Conclusion:Our present and previous data support the hypothesis that during early post-natal life, MD induces optic nerve terminals to release excessive glutamate in the LGN and this elevates nitric oxide and evokes apoptosis.
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