Barnes J M, Barnes N M, Costall B, Deakin J F, Ironside J W, Kilpatrick G J, Naylor R J, Rudd J A, Simpson M D, Slater P
Postgraduate Studies in Pharmacology, School of Pharmacy, University of Bradford, U.K.
Neurosci Lett. 1990 Mar 26;111(1-2):80-6. doi: 10.1016/0304-3940(90)90348-d.
The present studies demonstrate the presence of specific [3H]GR65630 binding sites within the human brainstem using the techniques of in vitro receptor autoradiography and ligand binding to homogenates. Autoradiography revealed the greatest accumulation of specific binding in the area postrema and subpostrema (AP/ASP). A lower level of specific binding was identified in the nucleus tractus solitarius (excluding area subpostrema). No specific binding was evident in the remainder of the hindbrain at this level. Discrete dissection followed by ligand binding to homogenates revealed that the specific binding of [3H]GR65630 (defined by the presence of 30 microM metoclopramide) was differentially distributed with highest levels in the AP/ASP (112.1 fmol/mg protein) and lower levels in the dorsal vagal complex (nucleus tractus solitarius--excluding the area subpostrema--dorsal motor nucleus of the vagus and hypoglossal nucleus) (DVC) and olivary nucleus (ON) (22.9 and 3.9 fmol/mg, respectively). No specific binding was detectable in the reticular formation (RF) located ventral to the dorsal vagal complex. The specific [3H]GR65630 binding site was pharmacologically similar to the 5-HT3 receptor since the potent and selective 5-HT3 receptor antagonists ICS 205-930 and zacopride (100 nM) and the agonist 5-HT (10 microM) inhibited binding to the same extent as metoclopramide in each of the individual areas (90, 60 and 20% in the AP/ASP, DVC and ON, respectively). The 5-HT1-like and 5-HT2 receptor antagonist methysergide (10 microM) failed to compete for the binding site. 5-HT3 receptor recognition sites within the AP/ASP and the DVC may be functionally involved in the ability of 5-HT3 receptor antagonists to control emesis.
目前的研究利用体外受体放射自显影技术和配体与匀浆结合的方法，证实在人脑干中存在特异性的[3H]GR65630结合位点。放射自显影显示，在最后区和次最后区（AP/ASP）特异性结合的积累最为显著。在孤束核（不包括次最后区）中发现特异性结合水平较低。在此层面，后脑的其余部分未发现明显的特异性结合。通过离散解剖并结合配体与匀浆的实验表明，[3H]GR65630的特异性结合（由30微摩尔甲氧氯普胺的存在定义）分布存在差异，在AP/ASP中水平最高（112.1飞摩尔/毫克蛋白），在迷走神经背侧复合体（孤束核——不包括次最后区——迷走神经背运动核和舌下神经核）（DVC）和橄榄核（ON）中水平较低（分别为22.9和3.9飞摩尔/毫克）。在位于迷走神经背侧复合体腹侧的网状结构（RF）中未检测到特异性结合。特异性的[3H]GR65630结合位点在药理学上与5-HT3受体相似，因为强效且选择性的5-HT3受体拮抗剂ICS 205-930和扎考必利（100纳摩尔）以及激动剂5-HT（10微摩尔）在各个区域与甲氧氯普胺抑制结合的程度相同（在AP/ASP、DVC和ON中分别为90%、60%和20%）。5-HT1样和5-HT2受体拮抗剂麦角新碱（10微摩尔）未能竞争该结合位点。AP/ASP和DVC中的5-HT3受体识别位点可能在功能上参与了5-HT3受体拮抗剂控制呕吐的能力。
