Somatostatin receptors in the human cerebellum during development

The ontogeny of somatostatin receptors (SRIF-R) was studied in the human cerebellum from mid-gestation to the 15th month postnatal. The brains were collected 3-26 h after death, from 18 fetuses and infants, and from 4 adults aged from 48 to 82. SRIF-R were characterized by membrane-binding assay and their localization was determined by in vitro autoradiography. Both techniques were conducted with two radio-ligands: [125I-Tyr0, DTrp8]S14 and D-Phe-Cys-125I-Tyr-DTrp-Lys-Thr- ol (125I-SMS 204-090). Membrane-binding studies carried out with each radioligand showed the presence of a single population of saturable, high affinity binding sites. Neither were the Kd values for either ligand (assessed by Scatchard analysis) changed appreciably during development, mean Kd values being 0.36 +/- 0.04 nM and 0.56 +/- 0.11 nM for [125I-Tyr0,DTrp8]S14 and 125I-SMS 204-090, respectively. Although inter-individual fluctuations of the Bmax were observed, the concentration of SRIF-R in the cerebellum of fetuses and infants up to 8 months appeared to be at least 2- to 10-fold higher than in the adult cerebellum. No appreciable differences in the Bmax values were found using either radioligand. The highest density of SRIF-R was observed in the cerebellar cortex of fetuses, in particular in the external granule cell layer (EGC), where stem cells of the granule cells are generated and enter the differentiation process. A high density of SRIF-R also occurred in the internal granule cell layer.(ABSTRACT TRUNCATED AT 250 WORDS)