title: Quantitative radioautographic study of somatostatin receptors heterogeneity in the rat extrahypothalamic brain.
abstract: The possible heterogeneity of extrahypothalamic somatostatin receptors was studied in rat brain by quantitative radioautography. The respective distribution and relative proportion of two somatostatin receptor sub-types (SS1 and SS2) were assessed by using two radioligands, the non-selective probe [125I]Tyr3-D-Trp8-somatostatin14 and the SS1 selective analogue [125I]Tyr3-SMS 201-995. For both ligands, adjacent brain sections were processed in the presence of micromolar concentrations of either a non-discriminative competitor (somatostatin14) or SS1-selective analogue (SMS 201-995). The comparative analysis of the specific binding remaining in the presence of each non-radioactive competitor permitted a semi-quantitative analysis of the proportion of SS1 and SS2 receptor sub-types in each brain region examined. Data obtained correlate well with homogenate binding results reported previously [Reubi J. C. (1984) Neurosci. Lett. 49, 259-263]. Although the distribution patterns obtained with both radioligands were similar, [125I]Tyr3-SMS 201-995 labelled only a fraction of [125I]Tyr0-D-Trp8-somatostatin14-labelled sites in certain brain regions. For example, both superficial and deep cortical laminae, as well as the basolateral amygdaloid nucleus and CA1 hippocampal area exhibited different binding densities with [125I]Tyr0-D-Trp8-somatostatin14 depending on the competitor used in the assay (somatostatin14 or SMS 201-995). On the other hand, [125I]Tyr3-SMS 201-995 binding was eliminated in an identical fashion by either competitor in these very same brain areas. This suggests the existence of SS1 and SS2 somatostatin receptor sub-types in these regions. In all other brain areas examined, somatostatin receptor sites are apparently of the SS1 sub-type. The heterogeneity of somatostatin receptors observed in certain regions may have relevance for the various biological effects induced by somatostatin in the central nervous system.
authors.affiliation: Institut for Biological Research, Dr. S. Stankovic, Beograd, Yugoslavia.
authors.forename: S
authors.initials: S
authors.lastname: Krantic
authors.forename: J C
authors.initials: JC
authors.lastname: Martel
authors.forename: D
authors.initials: D
authors.lastname: Weissmann
authors.forename: J F
authors.initials: JF
authors.lastname: Pujol
authors.forename: R
authors.initials: R
authors.lastname: Quirion
mesh_terms: D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D015282:Octreotide / Q000031:analogs & derivatives / Q000378:metabolism; D009928:Organ Specificity; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000032:analysis / Q000378:metabolism*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000031:analogs & derivatives / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; C045210:3-Tyr-octreotide; D013004:Somatostatin; C012088:somatostatin, N-Tyr(1)-; D015282:Octreotide