Omeljaniuk R J
Department of Biology, Lakehead University, Thunder Bay, ON, Canada.
Can J Physiol Pharmacol. 1995 May;73(5):585-93. doi: 10.1139/y95-074.
Dopamine, a catecholamine neurohormone, modulates pituitary hormone release in teleost fishes and other vertebrates. The existence and binding parameters of a pituitary dopamine-neuroleptic receptor from trout were examined and compared with those from goldfish. Pituitary homogenate was incubated with [3H]spiperone (D2 antagonist) under several experimental paradigms; incubations were terminated by filtration and bound 3H radioactivity was assessed by liquid scintillation spectroscopy. Specific binding of [3H]spiperone was tissue dependent. Equilibrium displacement analyses using domperidone (D2 antagonist) indicated a single class of binding site (LIGAND) with Kd = 2.49 +/- 0.89 microM and a capacity of 3.10 +/- 0.45 nmol/mg protein; the goldfish Kd and capacity were both significantly (p < 0.05) larger: Kd = 4.63 +/- 0.30 microM and capacity = 20.66 +/- 2.03 nmol/mg protein. The Kd and capacity for the trout pars distalis (2.45 +/- 0.33 microM and 3.27 +/- 0.24 nmol/mg protein, respectively) did not differ significantly (p < 0.05) from that of the neurointermediate lobe (2.50 +/- 0.08 microM and 3.58 +/- 0.56 nmol/mg protein, respectively). Dopamine D2 receptor ligands differentially displaced [3H]spiperone from the trout pituitary, while D1 ligands, a D4 ligand, and a 5-hydroxytryptamine (5HT2) receptor antagonist had only small nonspecific effects. Comparison of the trout and goldfish pituitary dopamine-neuroleptic receptor indicates conservation of receptor affinity (Kd); however, differences in receptor numbers and in the distribution of receptors between the pars distalis and neurointermediate lobe in the two species may be due in part to species or developmental differences, and may reflect differences in the role(s) and degrees of influence of dopamine in these fishes.
多巴胺作为一种儿茶酚胺神经激素，可调节硬骨鱼类及其他脊椎动物垂体激素的释放。对虹鳟垂体多巴胺 - 抗精神病药物受体的存在情况及结合参数进行了检测，并与金鱼的相应参数进行了比较。垂体匀浆在多种实验范式下与[³H]螺哌隆（D₂拮抗剂）共同孵育；孵育结束后通过过滤终止反应，结合的³H放射性通过液体闪烁光谱法进行评估。[³H]螺哌隆的特异性结合具有组织依赖性。使用多潘立酮（D₂拮抗剂）进行的平衡置换分析表明存在一类单一的结合位点（配体），解离常数（Kd）为2.49±0.89微摩尔，结合容量为3.10±0.45纳摩尔/毫克蛋白质；金鱼的Kd和结合容量均显著更大（p < 0.05）：Kd = 4.63±0.30微摩尔，结合容量 = 20.66±2.03纳摩尔/毫克蛋白质。虹鳟远侧部的Kd和结合容量（分别为2.45±0.33微摩尔和3.27±0.24纳摩尔/毫克蛋白质）与神经中间叶的Kd和结合容量（分别为2.50±0.08微摩尔和3.58±0.56纳摩尔/毫克蛋白质）相比，差异不显著（p < 0.05）。多巴胺D₂受体配体对虹鳟垂体中的[³H]螺哌隆有不同程度的置换作用，而D₁配体、一种D₄配体和一种5 - 羟色胺（5HT₂）受体拮抗剂仅有较小的非特异性作用。虹鳟和金鱼垂体多巴胺 - 抗精神病药物受体的比较表明受体亲和力（Kd）具有保守性；然而，这两个物种远侧部和神经中间叶之间受体数量及受体分布的差异可能部分归因于物种或发育差异，并且可能反映了多巴胺在这些鱼类中的作用及影响程度的差异。
