Kawaguchi Aya, Sato Masaki, Kimura Maki, Yamazaki Takaki, Yamamoto Hitoshi, Tazaki Masakazu, Ichinohe Tatsuya, Shibukawa Yoshiyuki
Department of Dental Anesthesiology, Tokyo Dental College Tokyo, Japan.
Department of Physiology, Tokyo Dental College Tokyo, Japan.
Front Cell Neurosci. 2015 Jun 15;9:229. doi: 10.3389/fncel.2015.00229. eCollection 2015.
Bradykinin (BK) and its receptors (B1 and B2 receptors) play important roles in inflammatory nociception. However, the patterns of expression and physiological/pathological functions of B1 and B2 receptors in trigeminal ganglion (TG) neurons remain to be fully elucidated. We investigated the functional expression of BK receptors in rat TG neurons. We observed intense immunoreactivity of B2 receptors in TG neurons, while B1 receptors showed weak immunoreactivity. Expression of the B2 receptor colocalized with immunoreactivities against the pan-neuronal marker, neurofilament H, substance P, isolectin B4, and tropomyosin receptor kinase A antibodies. Both in the presence and absence of extracellular Ca(2+) ([Ca(2+)]o), BK application increased the concentration of intracellular free Ca(2+) ([Ca(2+)]i). The amplitudes of BK-induced [Ca(2+)]i increase in the absence of [Ca(2+)]o were significantly smaller than those in the presence of Ca(2+). In the absence of [Ca(2+)]o, BK-induced [Ca(2+)]i increases were sensitive to B2 receptor antagonists, but not to a B1 receptor antagonist. However, B1 receptor agonist, Lys-[Des-Arg(9)]BK, transiently increased [Ca(2+)]i in primary cultured TG neurons, and these increases were sensitive to a B1 receptor antagonist in the presence of [Ca(2+)]o. These results indicated that B2 receptors were constitutively expressed and their activation induced the mobilization of [Ca(2+)]i from intracellular stores with partial Ca(2+) influx by BK. Although constitutive B1 receptor expression could not be clearly observed immunohistochemically in the TG cryosection, cultured TG neurons functionally expressed B1 receptors, suggesting that both B1 and B2 receptors involve pathological and physiological nociceptive functions.
缓激肽（BK）及其受体（B1和B2受体）在炎性痛觉中发挥重要作用。然而，三叉神经节（TG）神经元中B1和B2受体的表达模式以及生理/病理功能仍有待充分阐明。我们研究了BK受体在大鼠TG神经元中的功能性表达。我们观察到TG神经元中B2受体有强烈的免疫反应性，而B1受体显示出较弱的免疫反应性。B2受体的表达与针对泛神经元标志物神经丝H、P物质、异凝集素B4和原肌球蛋白受体激酶A抗体的免疫反应性共定位。无论细胞外Ca(2+)（[Ca(2+)]o）存在与否，BK的应用都会增加细胞内游离Ca(2+)（[Ca(2+)]i）的浓度。在没有[Ca(2+)]o的情况下，BK诱导的[Ca(2+)]i增加幅度明显小于有Ca(2+)存在时的值。在没有[Ca(2+)]o的情况下，BK诱导的[Ca(2+)]i增加对B2受体拮抗剂敏感，但对B1受体拮抗剂不敏感。然而，B1受体激动剂Lys-[去-Arg(9)]BK可使原代培养的TG神经元中的[Ca(2+)]i短暂增加，并且在有[Ca(2+)]o存在时，这些增加对B1受体拮抗剂敏感。这些结果表明，B2受体组成性表达，其激活通过BK诱导细胞内储存的[Ca(2+)]i动员并伴有部分Ca(2+)内流。虽然在TG冰冻切片中通过免疫组织化学未能清楚观察到B1受体的组成性表达，但培养的TG神经元功能性表达B1受体，这表明B1和B2受体均参与病理和生理痛觉功能。
