Neuronal Vacuolation

I was amazed to follow the discussion about vacuoles in the dorsal root ganglia neurons (Toxicol Pathol 38, 554–59; 999; 39, 451–453). Vacuolation of neurons represents hydropic degeneration, which in the dorsal root ganglia may result in neuronal death and formation of nodules of Nageotte replacing the lost neurons. Obviously for some neuropathologists the only possible way neurons can die is through “apoptosis.” But this is not true. In our studies with toxicity of extremely high doses of pyridoxine (vitamin B6), we have demonstrated that cytoplasmic vacuoles can easily be produced experimentally and that they are harbingers of neuronal death (Krinke et al. 1981; Krinke et al. 1985; Krinke 1988). Neuronal vacuoles can appear spontaneously, especially in aging animals. They are unspecific, that is, not related to the chemical structure of the toxicant, and they can also be produced by trauma. In the context of “mad cow disease,” or bovine spongiform encephalopathy, the attention of European pathologists was focused on the occurrence of vacuolated neurons in the bovine brain. Examination of 378 bovine brains revealed that in 11.5% of the animals, there were large neuronal vacuoles in the brain stem, especially the red nucleus, that were nonspecific and spontaneous (Guarda and Fatzer 1995). More research into neuronal cytoplasmic vacuolation and its role as an alternative to apoptosis is needed.

Georg J. KrinkeProf., MVDr, Dipl ECVP, Eggstrasse 26, CH-4402, Frenkendorf, Switzerland