Transient expression of somatostatin sst2 receptors in rat cerebellar nuclei during development

Adult rat cerebellar nuclei contain a single population of [I-125][Leu(8),D -Trp(22),Tyr(25)]somatostatin-28 binding sites characterized as sst1 recept ors. In the present study, we have investigated the evolution of somatostat in receptors in rat cerebellar nuclei during development by means of quanti tative autoradiography on tissue sections. The binding of [I-125][Leu(8),D- Trp(22);Tyr(25)]somatostatin-28, observed in the primordium of the medial c erebellar nuclei at embryonic day 17, reached a maximum at postnatal day 7 or 10 in the different nuclei. Thereafter, the density of binding sites gra dually decreased to the adult level. Competition studies were performed usi ng the somatostatin analogues CH-288 and MK-678 as specific sst1 and sst2 l igands, respectively. Partial inhibition of the radioligand binding by CH-2 88 and MK-678 revealed the presence of a predominant population of sst1 fro m embryonic day 19-28 day postnatal and a minor population of sst2 receptor s. The use of [I-125]MK-678 as a radioligand confirmed the presence of a tr ansient population of sst2 receptors, suggesting that somatostatin could ac t on rat cerebellar nuclei via sst1 and/or sst2 receptors during developmen t. (C) 1999 Elsevier Science B.V. All rights reserved.