RESUMEN
Histochemical studies in rat dorsal thalamus demonstrate that 'non-specific' cholinesterase (ChE) enzyme activity is characteristic of neurons of the anterior dorsal (AD) and reuniens (Re) nuclei and in a cell group found as part of the central lateral (CL) and lateral dorsal (LD) nuclei. Extra-somatal ChE staining also is seen in the anterior ventral (AV) nucleus. Parallel histochemical studies in other rodents reveal slight ChE activity in neurons of the mouse AD and LD, but not in other thalamic nuclei. The dorsal thalami of hamsters, gerbils and guinea pigs show no detectable cellular staining of ChE, although low levels of extra-somatal ChE appear in AV and the internal medullary lamina. These data indicate that 'non-specific' cholinesterase activity is not found commonly in neurons of the dorsal thalamus and prominent ChE staining may be unique to the laboratory rat.