NEURONAL DEGENERATION IN THE GERBIL BRAIN-STEM IS ASSOCIATED WITH SPONGIFORM LESIONS

Spongiform lesions arise in dendrites and glia in the brainstem of dom estic Mongolian gerbils. Most pronounced within the cochlear nucleus ( CN), this disorder is dynamic and progressive; the lesions increase in number, size, and extent with age. It has not been clear whether thes e spongioid lesions either cause or are associated with significant ne ural degeneration. In contrast, feral Mongolian gerbils (wild-trapped in Tuva) and their offspring show few spongiform lesions. The Tuvan ge rbils provide an appropriate within-species control. We compared degen eration in the brainstem of domestic and Tuvan gerbils using the amino -cupric-silver (ACS) stain of de Olmos et al. [(1994) Neurotoxicol. Te ratol., 16:545-561]. Positive histologic controls were provided by cer ebellar stab wounds in domestic gerbils and by unilateral kainic acid injections into the CN of Tuvan gerbils. The ACS stain revealed extens ive degeneration of axons, terminals, dendrites, and neurons in the br ainstem of domestic gerbils. Neurodegeneration was most pronounced in the CN and was coextensive with spongiform lesions. Neurodegeneration was also seen in the trapezoid body, lateral lemniscus, and inferior c olliculus, but was less pronounced than in the CN. The cerebellar stab wounds resulted in silver-stained Purkinje cells restricted to the st ab wound local region. Kainic acid produced extensive neuronal and spo ngiform degeneration of the injected CN that was very similar to that spontaneously occurring in domestic gerbils. In contrast, the non-inje cted CN of Tuvan gerbils showed no neuronal or spongiform degeneration with the ACS stain. We conclude that, in domestic gerbils, the natura lly occurring spongiform lesions of the CN and the accompanying neurod egeneration are both results of a common mechanism, most probably exci totoxic. (C) 1998 Wiley-Liss, Inc.