Raskovsky S, Rivas E, Bernik D, Medina J, Jerusalinsky D
Instituto de Biologia Celular, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Mol Chem Neuropathol. 1990 Aug-Oct;13(1-2):17-32. doi: 10.1007/BF03159905.
The modulation of the binding of muscarinic cholinergic receptor ligands by phosphatidylserine purified from bovine cerebral cortex (BC-PS) was examined in vitro and in vivo. The enrichment of bovine cerebral cortical synaptosomal membranes with BC-PS, using a fusion technique, produced a concentration-dependent decrease in the affinity (increase in Kd) of [3H]quinuclidinyl benzylate (3H-QNB) specific binding to muscarinic acetylcholine receptors (mAChR), without changes in their maximal number (Bmax). Similar results were observed when [3H]oxotremorine (3H-OXO) was used to label a high affinity subpopulation of mAChR. On the other hand, preincubation of BC-PS liposomes with synaptosomal membranes in a nonoptimum fusion condition (at pH 7.4) did not alter the binding properties of both radioligands. Fusion experiments using a pure phosphatidylserine preparation from spinal cord revealed a similar decrement in the affinity of 3H-QNB specific binding. Five day's intraperitoneal (i.p.) administration of 15 mg/kg of BC-PS liposomes in rats increased the maximal number of cerebral cortical binding sites for 3H-OXO. Scatchard analysis revealed no changes in the apparent dissociation constant. This modification is selective in relation to the neural structure studied. Thus, BC-PS treatment did not modify 3H-OXO binding in the hippocampal formation and cerebellum. In contrast, parallel experiments using the muscarinic antagonist 3H-QNB showed no alteration in the binding properties of mAChR. Five day's i.p. administration of 15 mg/kg/d of phosphatidylcholine from bovine cerebral cortex (BC-PC) liposomes produced quite similar results to those obtained with BC-PS. These results indicate that mAChR are under the modulatory action of phosphatidylserine (PS) and phosphatidylcholine (PC), and suggest that this endogenous phospholipids may play a regulatory role on the mAChR. The possible implications of these findings on the effects of PC or PS treatment in neurological disorders involving a decrease in central cholinergic functions are discussed.
在体外和体内研究了从牛脑皮层纯化的磷脂酰丝氨酸（BC - PS）对毒蕈碱胆碱能受体配体结合的调节作用。采用融合技术用BC - PS富集牛脑皮层突触体膜，使[³H]喹核醇基苯甲酸酯（³H - QNB）与毒蕈碱型乙酰胆碱受体（mAChR）特异性结合的亲和力呈浓度依赖性降低（Kd增加），而其最大结合数（Bmax）不变。当用[³H]震颤素（³H - OXO）标记mAChR的高亲和力亚群时，观察到类似结果。另一方面，在非最佳融合条件（pH 7.4）下将BC - PS脂质体与突触体膜预孵育，并未改变两种放射性配体的结合特性。使用脊髓来源的纯磷脂酰丝氨酸制剂进行的融合实验显示³H - QNB特异性结合的亲和力有类似降低。给大鼠腹腔注射（i.p.）15 mg/kg的BC - PS脂质体，连续五天，可增加³H - OXO在大脑皮层结合位点的最大数量。Scatchard分析显示表观解离常数无变化。这种修饰相对于所研究的神经结构具有选择性。因此，BC - PS处理并未改变³H - OXO在海马结构和小脑中的结合。相反，使用毒蕈碱拮抗剂³H - QNB进行的平行实验显示mAChR的结合特性无改变。给大鼠腹腔注射15 mg/kg/d的牛脑皮层磷脂酰胆碱（BC - PC）脂质体，连续五天，产生的结果与BC - PS相当相似。这些结果表明mAChR受磷脂酰丝氨酸（PS）和磷脂酰胆碱（PC）的调节作用，提示这种内源性磷脂可能对mAChR发挥调节作用。讨论了这些发现对PC或PS治疗涉及中枢胆碱能功能降低的神经系统疾病的影响的可能意义。
