Somatostatin binding sites in the white matter of the developing human brainstem: inverse relationship with the myelination process.

The ontogeny of somatostatin binding sites was studied in eight fiber tracts of the human lower brainstem in 18 fetuses and infants aged from 21 weeks postconceptional to 6 months postnatal, and in two adults. The study was performed by means of quantitative autoradiography using [125I-Tyr0,DTrp8]somatostatin-14 as a radioligand. For all structures examined, the highest densities of binding sites were detected in the younger stages and the density of sites decreased during development. These results reveal the existence of a close inverse relationship between the density of somatostatin receptors and the myelination process in the fiber tracts of the human brainstem.