Leroux P, Gonzalez B J, Laquerrière A, Bodenant C, Vaudry H
Groupe de Recherche en Endocrinologie Moléculaire, Unité Alliée à I'INSERM, Faculté des Sciences, Université de Rouen, Mont-Saint-Aignan, France.
Neuroendocrinology. 1988 Jun;47(6):533-44. doi: 10.1159/000124966.
The radiolabelled somatostatin analogs [125I-Tyr0,DTrp8]S14 and [Leu8,DTrp22,125I-Tyr25]S28 were used as radioligands to study the distribution of somatostatin receptors in the rat hypothalamus. Previous studies have detected very few somatostatin-binding sites in the hypothalamus using in vitro autoradiography. Since the lack of autoradiographic labelling has been ascribed to the occupancy of the receptors by endogenous ligands, we have developed a method using guanosine triphosphate (GTP) pretreatment to unmask somatostatin receptors. Preincubation of brain slices with 10(-6) M GTP, by desaturating the occupied receptors, made it possible to reveal the wide distribution of somatostatin-binding sites in the rat hypothalamus. Somatostatin-14 binding site populations were observed in numerous hypothalamic areas including the preoptic area where the receptors likely account for self-inhibition of somatostatin release, the supraoptic nucleus, the bed nucleus of the stria terminalis, the anterior hypothalamic nucleus, the perifornical area, the zona incerta and a mediolateral area located laterally to the ventromedian and dorsomedian nuclei and limited laterally by the mammillo-thalamic tract, the fornix and the optic tract. All structures showing S14-binding sites were labelled by the S28 radioligand. In addition, the paraventricular parvocellular nucleus contained exclusively S28-binding sites, which could be involved in the inhibitory effect of S28 on CRF-mediated endocrine and sympathetic responses. A moderate density of S28-preferring sites was also detected in the periventricular nucleus. In summary, GTP preincubation of brain slices appeared to be a useful technique to reveal multiple somatostatin receptors populations in the brain. The widespread distribution of somatostatin receptors in the hypothalamus is in total agreement with the variety of physiological effects of the somatostatin peptide family.
放射性标记的生长抑素类似物[125I-Tyr0,DTrp8]S14和[Leu8,DTrp22,125I-Tyr25]S28被用作放射性配体，以研究生长抑素受体在大鼠下丘脑的分布。以往的研究使用体外放射自显影术在下丘脑中检测到的生长抑素结合位点非常少。由于放射自显影标记的缺乏被归因于内源性配体对受体的占据，我们开发了一种使用三磷酸鸟苷（GTP）预处理来揭示生长抑素受体的方法。用脑切片与10(-6) M GTP预孵育，通过使被占据的受体去饱和，有可能揭示生长抑素结合位点在大鼠下丘脑中的广泛分布。在许多下丘脑区域观察到生长抑素-14结合位点群体，包括视前区，其中的受体可能参与生长抑素释放的自我抑制、视上核、终纹床核、下丘脑前核、穹窿周区、未定带以及位于腹内侧核和背内侧核外侧且外侧受乳头体-丘脑束、穹窿和视束限制的中外侧区。所有显示S14结合位点的结构都被S28放射性配体标记。此外，室旁小细胞核仅含有S28结合位点，这可能与S28对促肾上腺皮质激素释放因子介导的内分泌和交感反应的抑制作用有关。在室周核中也检测到中等密度的偏好S28的位点。总之，脑切片的GTP预孵育似乎是一种揭示脑中多种生长抑素受体群体的有用技术。生长抑素受体在下丘脑中的广泛分布与生长抑素肽家族的多种生理效应完全一致。
