Serres F, Li Q, Garcia F, Raap D K, Battaglia G, Muma N A, Van de Kar L D
Department of Pharmacology, Stritch School of Medicine, Loyola University of Chicago, Maywood, Illinois 60153, USA.
J Neurosci. 2000 May 1;20(9):3095-103. doi: 10.1523/JNEUROSCI.20-09-03095.2000.
Using in situ hybridization and immunoblot analysis, the present studies identified G(z) mRNA and G(z)-protein in the hypothalamic paraventricular nucleus. The role of G(z)-proteins in hypothalamic 5-HT(1A) receptor signaling was examined in vivo. Activation of 5-HT(1A) receptors increases the secretion of oxytocin and ACTH, but not prolactin. Intracerebroventricular infusion (3-4 d) of G(z) antisense oligodeoxynucleotides, with different sequences and different phosphorothioate modification patterns, reduced the levels of G(z)-protein in the hypothalamic paraventricular nucleus, whereas missense oligodeoxynucleotides had no effect. Neither antisense nor missense oligodeoxynucleotide treatment altered basal plasma levels of ACTH, oxytocin, or prolactin, when compared with untreated controls. An antisense-induced decrease in hypothalamic G(z)-protein levels was paralleled by a significant decrease in the oxytocin and ACTH responses to the 5-HT(1A) agonist 8-hydroxy-dipropylamino-tetralin (8-OH-DPAT). In contrast, the prolactin response to 8-OH-DPAT (which cannot be blocked by 5-HT(1A) antagonists) was not inhibited by G(z) antisense oligodeoxynucleotides. G(z)-proteins are the only members of the G(i)/G(o)-protein family that are not inactivated by pertussis toxin. In a control experiment, pertussis toxin treatment (1 microgram/5 microliter, i.c.v.; 48 hr before the 8-OH-DPAT challenge) did not inhibit the ACTH response, potentiated the oxytocin response, and eliminated the prolactin response to 8-OH-DPAT. Thus, pertussis toxin-sensitive G(i)/G(o)-proteins do not mediate the 5-HT(1A) receptor-mediated increase in ACTH and oxytocin secretion. Combined, these studies provide the first in vivo evidence for a key role of G(z)-proteins in coupling hypothalamic 5-HT(1A) receptors to effector mechanisms.
本研究采用原位杂交和免疫印迹分析方法，在下丘脑室旁核中鉴定出G(z)信使核糖核酸和G(z)蛋白。对G(z)蛋白在体内下丘脑5-羟色胺(1A)受体信号传导中的作用进行了研究。5-羟色胺(1A)受体的激活会增加催产素和促肾上腺皮质激素的分泌，但不会增加催乳素的分泌。脑室内注入（3 - 4天）不同序列和不同硫代磷酸酯修饰模式的G(z)反义寡脱氧核苷酸，可降低下丘脑室旁核中G(z)蛋白的水平，而错义寡脱氧核苷酸则无此作用。与未处理的对照组相比，反义寡脱氧核苷酸和错义寡脱氧核苷酸处理均未改变促肾上腺皮质激素、催产素或催乳素的基础血浆水平。下丘脑G(z)蛋白水平因反义寡脱氧核苷酸诱导而降低，同时对5-羟色胺(1A)激动剂8-羟基-二丙基氨基-四氢萘（8-OH-DPAT）的催产素和促肾上腺皮质激素反应也显著降低。相比之下，G(z)反义寡脱氧核苷酸并未抑制对8-OH-DPAT的催乳素反应（该反应不能被5-羟色胺(1A)拮抗剂阻断）。G(z)蛋白是G(i)/G(o)蛋白家族中唯一不受百日咳毒素失活影响的成员。在一项对照实验中，百日咳毒素处理（1微克/5微升，脑室内注射；在8-OH-DPAT激发前48小时）并未抑制促肾上腺皮质激素反应，反而增强了催产素反应，并消除了对8-OH-DPAT的催乳素反应。因此，对百日咳毒素敏感的G(i)/G(o)蛋白并不介导5-羟色胺(1A)受体介导的促肾上腺皮质激素和催产素分泌增加。综合来看，这些研究首次在体内证明了G(z)蛋白在下丘脑5-羟色胺(1A)受体与效应器机制偶联中起关键作用。
