Dupuis D S, Palmier C, Colpaert F C, Pauwels P J
Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres, France.
J Neurochem. 1998 Mar;70(3):1258-68. doi: 10.1046/j.1471-4159.1998.70031258.x.
G protein activation mediated by serotonin 5-HT1A and 5-HT(1B/D) receptors in guinea pig brain was investigated by using quantitative autoradiography of agonist-stimulated [35S]GTPgammaS binding to brain sections. [35S]GTPgammaS binding was stimulated by the mixed 5-HT1A/5-HT(1B/D) agonist L694247 in brain structures enriched in 5-HT1A binding sites, i.e., hippocampus (+140 +/- 14%), dorsal raphe (+70 +/- 8%), lateral septum (+52 +/- 12%), cingulate (+36 +/- 8%), and entorhinal cortex (+34 +/- 5%). L694247 caused little or no stimulation of [35S]GTPgammaS binding in brain regions with high densities of 5-HT(1B/D) binding sites (e.g., substantia nigra, striatum, central gray, and dorsal subiculum). The [35S]GTPgammaS binding response was antagonized by WAY100635 (10 microM) and methiothepin (10 microM). In contrast, the 5-HT1B inverse agonist SB224289 (10 microM) did not affect the L694247-mediated [35S]GTPgammaS binding response, and the mixed 5-HT(1B/D) antagonist GR127935 (10 microM) yielded a partial blockade. The distribution pattern of the [35S]GTPgammaS binding response and the antagonist profile suggest the L694247-mediated response in guinea pig brain to be mediated by 5-HT1A receptors. In addition to L694247, 8-hydroxy-2-(di-n-propylamino)tetralin, and flesinoxan also stimulated [35S]GTPgammaS binding; their maximal responses varied between 46 and 52% compared with L694247, irrespective of the brain structure being considered. Sumatriptan, rizatriptan, and zolmitriptan (10 microM) stimulated [35S]GTPgammaS binding in the hippocampus by 20-50%. Naratriptan, CP122638, and dihydroergotamine stimulated [35S]GTPgammaS binding to a similar level as L694247 in hippocampus, lateral septum, and dorsal raphe. It appears that under the present experimental conditions, G protein activation through 5-HT1A but not 5-HT(1B/D) receptors can be measured in guinea pig brain sections.
通过对激动剂刺激的[35S]GTPγS与脑切片结合进行定量放射自显影，研究了豚鼠脑中5-羟色胺5-HT1A和5-HT(1B/D)受体介导的G蛋白激活。在富含5-HT1A结合位点的脑结构中，即海马体（增加140±14%）、中缝背核（增加70±8%）、外侧隔区（增加52±12%）、扣带回（增加36±8%）和内嗅皮质（增加34±5%），混合5-HT1A/5-HT(1B/D)激动剂L694247刺激了[35S]GTPγS结合。L694247在具有高密度5-HT(1B/D)结合位点的脑区（如黑质、纹状体、中央灰质和背侧下托）对[35S]GTPγS结合几乎没有刺激作用或根本没有刺激作用。[35S]GTPγS结合反应被WAY100635（10微摩尔）和甲硫哒嗪（10微摩尔）拮抗。相反，5-HT1B反向激动剂SB224289（10微摩尔）不影响L694247介导的[35S]GTPγS结合反应，而混合5-HT(1B/D)拮抗剂GR127935（10微摩尔）产生部分阻断作用。[35S]GTPγS结合反应的分布模式和拮抗剂特征表明，豚鼠脑中L694247介导的反应是由5-HT1A受体介导的。除了L694247外，8-羟基-2-（二正丙基氨基）四氢萘和氟司立辛也刺激了[35S]GTPγS结合；与L694247相比，无论考虑何种脑结构，它们的最大反应在46%至52%之间变化。舒马曲坦、利扎曲坦和佐米曲坦（10微摩尔）使海马体中的[35S]GTPγS结合增加20 - 50%。那拉曲坦、CP122638和双氢麦角胺在海马体、外侧隔区和中缝背核中刺激[35S]GTPγS结合的水平与L694247相似。看来在目前的实验条件下，在豚鼠脑切片中可以检测到通过5-HT1A而非5-HT(1B/D)受体激活的G蛋白。
