Preprotachykinin-A mRNA expression in the human and monkey brain: An in situ hybridization study

The mRNA expression for preprotachykinin-A (PPT-A) was studied throughout the human and cynomolgus monkey brain to assess the neuroanatomical expression pattern of the PPT-A gene in primates. In situ hybridization showed that the PPT-A mRNA is expressed highly in specific regions of the postmortem human brain, including the striatum, islands of Calleja, hypothalamus (posterior, premammillary, medial mammillary, and ventromedial nuclei), superior and inferior colliculi, periaqueductal gray, and oculomotor nuclear complex. PPT-A mRNA-expressing neurons also were present in the paranigralis (ventral tegmental area) and were scattered in the bed nucleus stria terminalis throughout the sublenticular substantia innominata region, including the diagonal band of Broca and the nucleus basalis of Meynert. In the hippocampus, high PPT-A mRNA expression was localized predominantly to the polymorphic layer of the dentate gyrus; no labeled cells were present in the granular layer. Positively labeled cells also were found scattered in the CA regions as well as in the amygdaloid complex. Neocortical expression of PPT-A mRNA was localized mainly to the deep laminae (layers V/VI), except for the striate cortex (labeling was seen also in superficial layers). The subiculum, thalamus, globus pallidus, ventral pallidum, substantia nigra pars compacta, red nucleus, pontine nuclei, and cerebellum were characterized by very weak to undetectable expression of PPT-A mRNA. An expression pattern was evident in the monkey forebrain similar to that observed in the human, except for the absence of PPT mRNA-expressing cells in the medial mammillary nucleus despite intense expression in supramammillary, lateral mammillary, and premammillary nuclei. Overall, more similarities than differences are apparent between primate species in the expression pattern of the PPT-A gene. J. Comp. Neurol. 411;56-72, 1999.