Platelets as a marker of adrenergic and serotonergic receptors in dogs

本研究在前人研究的基础上，探讨了血小板活性作为犬肾上腺素能、非肾上腺素能和肾上腺素能受体的标志物，即脑内单胺，特别是5-羟色胺参与α_2-肾上腺素能受体介导的呕吐的调节。本研究证实<2A>犬血小板上存在α-肾上腺素受体亚型，这种受体参与介导肾上腺素增强的血小板聚集。犬内毒素休克时α_2-肾上腺素受体结合与α_2-肾上腺素受体介导的心血管效应的研究结果表明，血小板和脑间α_2-肾上腺素受体数量的减少与α_2-肾上腺素受体激动剂心血管效应的减弱呈显著正相关。因此，<2A>犬内毒素休克时，中枢神经系统和外周血管系统的α-肾上腺素能受体活性均受到损害。这些结果表明，血小板可部分反映交感-肾上腺神经活动激活时和激活后中枢神经系统和外周血管系统α_2-肾上腺素能受体的变化。另一方面，本研究证实咪唑（in）e（I）结构对肾上腺素增强的犬血小板聚集有抑制作用，并证实犬血小板上存在两种非肾上腺素能I受体亚型I_1和I_2。此外，本研究还提示I_1亚型与GTP结合蛋白偶联，而I_2亚型与GTP结合蛋白不偶联。犬血小板I_1、I_2受体和5-HT受体的功能尚需进一步研究。

The present study was conducted to investigate the platelet activity as a marker of adrenergic, non-adrenergic, and serotonergic receptors in dogs, based on previous findings that monoamine, and in particular 5-hydroxytryptamine in the brain, are involved in the regulation of α_2-adrenoceptor-mediated emesis. This study demonstrated that the α_<2A>-adrenoceptor subtype exists on canine platelets, and this type of receptors was involved in the mediation of adrenaline-potentiated platelet aggregation. The results of α_2-adrenoceptor binding and the α_2-adrenoceptor-mediated cardiovascular effects during canine endotoxin shock revealed that significant positive correlations were observed for reduced number of α_2-adrenoceptors between platelets and brain, and diminished cardiovascular effects of α_2-adrenoceptor agonists. Therefore, the α_<2A>-adrenoceptor activity was impaired in the central nervous system as well as in the peripheral vascular system during canine endotoxin shock. These results indicated that platelets may in part represent a good model which reflects the α_2-adrenoceptor changes in the central nervous system and peripheral vascular system during and after activation of sympatho-adrenal nerve activity. On the other hand, this study demonstrated that imidazol(in)e (I) structure has a role for inhibition of adrenaline-potentiated platelet aggregation in dogs, and that two subtypes of non-adrenergic I receptors, I_1 and I_2, exist on canine platelets. In addition, this study suggested that I_1 subtype was coupled with GTP-binding proteins, and I_2 was not coupled with those. Further studies may be required to investigate the function of I_1 and I_2 receptors as well as 5-HT receptors in canine platelets.