Gómez-Villafuertes R, Gualix J, Miras-Portugal M T
Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain.
J Neurochem. 2001 Apr;77(1):84-93. doi: 10.1046/j.1471-4159.2001.t01-1-00228.x.
GABAergic terminals from rat midbrain characterized by immunolocalization of glutamic acid decarboxylase and/or the vesicular inhibitory amino acid transporter respond to ATP or P(1),P(5)-di(adenosine-5') pentaphosphate (Ap(5)A) with an increase in the intrasynaptosomal calcium concentration measured by a microfluorimetric technique in single synaptic terminals. The ATP response is mediated through the activation of P2X receptors with an abundant presence of P2X(3) subunits. Ap(5)A, however, exerts its effects by acting through a different receptor termed the dinucleotide receptor. Both receptors, once activated in the presence of extrasynaptosomal calcium, induce a concentration-dependent GABA release from synaptosomal populations with EC(50) values of 16 and 20 microM for ATP and Ap(5)A, respectively. Specific inhibition of GABA release is obtained with pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (80 microM) on the ATP effect and with P(1),P(5)-di(inosine-5') pentaphosphate (100 nM) on the dinucleotide receptor.
通过谷氨酸脱羧酶和/或囊泡抑制性氨基酸转运体的免疫定位表征的来自大鼠中脑的γ-氨基丁酸能终末，对ATP或P(1),P(5)-二(腺苷-5')五磷酸(Ap(5)A)产生反应，通过微荧光技术在单个突触终末中测量的突触小体内钙浓度增加。ATP反应是通过具有丰富P2X(3)亚基的P2X受体的激活介导的。然而，Ap(5)A通过作用于一种称为二核苷酸受体的不同受体发挥其作用。一旦在突触外钙存在的情况下被激活，这两种受体都会诱导突触小体群体中浓度依赖性的γ-氨基丁酸释放，ATP和Ap(5)A的半数有效浓度(EC(50))值分别为16和20微摩尔。用磷酸吡哆醛-6-偶氮苯基-2',4'-二磺酸(80微摩尔)对ATP效应进行特异性抑制，并用P(1),P(5)-二(肌苷-5')五磷酸(100纳摩尔)对二核苷酸受体进行特异性抑制。
