Evidence for the existence of three classes of neurokinin receptors in brain. Differential ontogeny of neurokinin-1, neurokinin-2 and neurokinin-3 binding sites in rat cerebral cortex.

The autoradiographic distribution of the 3 neurokinin (NK) receptor sub-types, NK-1, NK-2 and NK-3, was compared in rat cerebral cortex during post-natal development using [125I]Bolton-Hunter-substance P, (2-[125I]iodohistidyl1)neurokinin A and [125I]Bolton-Hunter-eledoisin as respective radioligands. Throughout brain development, NK-1 receptor sites are present in low densities with some enrichment seen in lamina III while NK-3 binding sites are concentrated in layers IV and V. However, it appears that NK-2 receptors are mostly expressed in lamina VI and only during the first two postnatal weeks. These results demonstrate further the existence and differential ontogeny of 3 classes of NK receptors in rat brain cortex.