NK-1 receptor immunoreactivity in distinct morphological types of lamina I neurons of the primate spinal cord Yu, Xiao Zhang, En Craig, Arthur Shigemoto, Ryuichi ; https://orcid.org/0000-0001-8761-9444 Ribeiro Da Silva, Alfredo De Koninck, Yves In cat and monkey, lamina I cells can be classified into three basic morphological types (fusiform, pyramidal, and multipolar), and recent intracellular labeling evidence in the cat indicates that fusiform and multipolar lamina I cells are two different types of nociceptive cells, whereas pyramidal cells are innocuous thermoreceptive-specific. Because earlier observations indicated that only nociceptive dorsal horn neurons respond to substance P (SP), we examined which morphological types of lamina I neurons express receptors for SP (NK-1r). We categorized NK-1r- immunoreactive (IR) lamina I neurons in serial horizontal sections from the cervical and lumbar enlargements of four monkeys. Consistent results were obtained by two independent teams of observers. Nearly all NK-1r-IR cells were fusiform (42%) or multipolar (43%), but only 6% were pyramidal (with 9% unclassified). We obtained similar findings in three monkeys in which we used double-labeling immunocytochemistry to identify NK-1r-IR and spinothalamic lamina I neurons retrogradely labeled with cholera toxin subunit b from the thalamus; most NK-1r-IR lamina I spinothalamic neurons were fusiform (48%) or multipolar (33%), and only 10% were pyramidal. In contrast, most (~75%) pyramidal and some (~25%) fusiform and multipolar lamina I spinothalamic neurons did not display NK-1r immunoreactivity. These data indicate that most fusiform and multipolar lamina I neurons in the monkey can express NK-1r, consistent with the idea that both types are nociceptive, whereas only a small proportion of lamina I pyramidal cells express this receptor, consistent with the previous finding that they are nonnociceptive. However, these findings also indicate that not all nociceptive lamina I neurons express receptors for SP. Society for Neuroscience 1999 info:eu-repo/semantics/article doc-type:Article Article http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/2593 Yu X, Zhang E, Craig A, Shigemoto R, Ribeiro Da Silva A, De Koninck Y. NK-1 receptor immunoreactivity in distinct morphological types of lamina I neurons of the primate spinal cord. <i>Journal of Neuroscience</i>. 1999;19(9):3545-3555. doi:<a href="https://doi.org/10.1523/JNEUROSCI.19-09-03545.1999">10.1523/JNEUROSCI.19-09-03545.1999</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1523/JNEUROSCI.19-09-03545.1999 info:eu-repo/semantics/altIdentifier/issn/0270-6474 info:eu-repo/semantics/altIdentifier/pmid/10212314 info:eu-repo/semantics/openAccess