Hu Hong-Zhen, Gao Na, Liu Sumei, Ren Jun, Xia Yun, Wood Jackie D
Department of Physiology and Cell Biology, College of Medicine and Public Health, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210-1218, USA.
J Pharmacol Exp Ther. 2004 Apr;309(1):310-9. doi: 10.1124/jpet.103.059204. Epub 2004 Jan 12.
Intracellular recording methods with "sharp" microelectrodes were used to study signal transduction mechanisms underlying the excitatory action of bradykinin (BK) in morphologically identified neurons in the small intestinal submucosal plexus. Exposure to BK evoked slowly activating membrane depolarization and enhanced excitability associated with increased input resistance in AH-type and decreased input resistance in S-type neurons. Preincubation with pertussis toxin did not affect the BK-evoked responses. Pretreatment with the cyclooxygenase inhibitors indomethacin or piroxicam suppressed or abolished the BK-evoked responses. Application of prostaglandin (PG) E(2) or PG analogs evoked BK-like depolarizing responses in the submucosal plexus with a potency order of PGE(2) > PGE(1) > 17-phenyl trinor-PGE(2) > PGI(2) > sulprostone > PGF(2alpha). Depolarizing responses to bradykinin or PGE(2) in S-type neurons were suppressed in the presence of the phospholipase C inhibitor U73122 [(1-6-[([17beta]-3-methoxyestra-1,3,5[10]-tren-17-71)amino]hexyl)-1H-pyrrole-2,5-dione)], but not the inactive analog U73343 [(1-6-[([17beta]-3-methoxyestra-1,3,5[10]trien-17yl)amino]hexyl)-2,5-pyrrolidinedione)]. The inositol-1,4,5-trisphosphate receptor antagonist 2-aminoethoxy-diphenylborane and the calmodulin inhibitor W-7, but not ryanodine, suppressed both bradykinin- and PGE(2)-evoked responses. KN-62, an inhibitor of calmodulin kinases, or GF109203X, a specific protein kinase C inhibitor, suppressed both BK- and PGE(2)-evoked depolarizing responses. Selective protein kinase A inhibitors did not alter BK- or PGE(2)-evoked depolarizing responses in S neurons. The results suggest that BK stimulates synthesis and release of PGE(2), which acts at EP(1) receptors to evoke depolarizing responses in submucosal neurons. The postreceptor transduction cascade includes activation of phospholipase C, inositol-1,4,5-trisphosphate production, intraneuronal Ca2+ mobilization, activation of protein kinase C and/or calmodulin kinases, and phosphorylation of cationic channels.
采用“尖锐”微电极的细胞内记录方法，研究缓激肽（BK）在小肠黏膜下神经丛形态学鉴定神经元中的兴奋作用所涉及的信号转导机制。暴露于BK可诱发缓慢激活的膜去极化，并增强兴奋性，AH型神经元的输入电阻增加，S型神经元的输入电阻降低。用百日咳毒素预孵育不影响BK诱发的反应。用环氧化酶抑制剂吲哚美辛或吡罗昔康预处理可抑制或消除BK诱发的反应。应用前列腺素（PG）E2或PG类似物在黏膜下神经丛中诱发类似BK的去极化反应，其效力顺序为PGE2＞PGE1＞17-苯基三降-PGE2＞PGI2＞舒前列素＞PGF2α。在磷脂酶C抑制剂U73122[（1-6-[（[17β]-3-甲氧基雌甾-1,3,5[10]-三烯-17-71）氨基]己基）-1H-吡咯-2,5-二酮]存在下，S型神经元对缓激肽或PGE2的去极化反应受到抑制，但无活性类似物U73343[（1-6-[（[17β]-3-甲氧基雌甾-1,3,5[10]三烯-17基）氨基]己基）-2,5-吡咯烷二酮]则无此作用。肌醇-1,4,5-三磷酸受体拮抗剂2-氨基乙氧基-二苯硼烷和钙调蛋白抑制剂W-7可抑制缓激肽和PGE2诱发的反应，但ryanodine则无此作用。钙调蛋白激酶抑制剂KN-62或特异性蛋白激酶C抑制剂GF109203X可抑制BK和PGE2诱发的去极化反应。选择性蛋白激酶A抑制剂不改变S神经元中BK或PGE2诱发的去极化反应。结果表明，BK刺激PGE2的合成和释放，PGE2作用于EP1受体在黏膜下神经元中诱发去极化反应。受体后转导级联反应包括磷脂酶C的激活、肌醇-1,4,5-三磷酸的产生、神经元内Ca2+的动员、蛋白激酶C和/或钙调蛋白激酶的激活以及阳离子通道的磷酸化。
