The diversity of nNOS gene expression in avulsion-injured spinal motoneurons among laboratory rodents.

Rats, mice, and hamsters are commonly used laboratory rodents in the experimental modeling strategies of avulsion-induced motoneuron degenerations. It is necessary to study the species-specific gene expression in spinal cord in response to avulsion. We carried out the brachial roots avulsion in all animals and compared the survival and nNOS gene expression in injured motoneurons and spinal segments among the three species. The results showed that avulsion-induced loss of motoneurons was greatest in mice than that in hamsters or rats. Avulsion induced decrease of nNOS mRNA level in injured spinal segments in all three species, but greater in amplitude in rats and mice than that in hamsters. However, the de novo nNOS protein expression in injured motoneurons was higher in rats than in hamsters, none in mice. This study strongly suggests that the species diversity of nNOS gene must be considered when estimating the role of nNOS in motoneuron degenerations.