Fleminger S
Department of Neurology, Institute of Psychiatry, London, U.K.
Biochem Pharmacol. 1991 Jul 5;42(2):229-37. doi: 10.1016/0006-2952(91)90708-d.
The relationship between occupation of the D-1 dopamine receptor by [3H]piflutixol and inhibition of dopamine-sensitive adenylate cyclase has been studied. Experiments were performed in parallel; after the initial incubation to enable binding of [3H]piflutixol, half the tubes were assayed for [3H]piflutixol binding and the other half assayed for adenylate cyclase activity. The assay conditions for the two halves of the experiments were identical. (+/-)Sulpiride (3 x 10(-5)M) was present in all tubes to mask drug binding to the D-2 receptor. The inhibition of dopamine- (10(-3) and 10(-5)M) sensitive adenylate cyclase with increasing concentrations of [3H]piflutixol in the incubation mixture was compared to the saturation of specific [3H]piflutixol binding with those same concentrations of [3H]piflutixol. There was a linear relationship between receptor occupation by [3H]piflutixol and inhibition of dopamine sensitive adenylate cyclase. In a second experiment dopamine was present during the initial incubation with [3H]piflutixol. This resulted in a displacement of specific [3H]piflutixol binding and, as a consequence, a reduction of [3H]piflutixol's inhibition of dopamine-sensitive adenylate cyclase. In the absence of GTP in the initial incubation dopamine produced a greater reduction of [3H]piflutixol's inhibition of dopamine adenylate cyclase than displacement of specific [3H]piflutixol binding. In the presence of GTP in the initial incubation both displacement curves were shifted to the right, i.e. dopamine was less potent. However, under these conditions dopamine produced less inhibition of [3H]piflutixol's inhibition of dopamine adenylate cyclase than displacement of specific [3H]piflutixol binding. These results are interpreted as resulting from changes in D-1high and D-1low ratios as a result of incubation in the presence or absence of GTP.
研究了[3H]匹氟噻吨对D-1多巴胺受体的占据与多巴胺敏感腺苷酸环化酶抑制之间的关系。实验并行进行；在进行初始孵育以使[3H]匹氟噻吨结合后，一半试管用于检测[3H]匹氟噻吨结合情况，另一半用于检测腺苷酸环化酶活性。实验的这两部分的检测条件相同。所有试管中均加入（±）舒必利（3×10^(-5)M）以掩盖药物与D-2受体的结合。将孵育混合物中[3H]匹氟噻吨浓度增加时多巴胺（10^(-3)和10^(-5)M）敏感腺苷酸环化酶的抑制情况与相同浓度[3H]匹氟噻吨的特异性[3H]匹氟噻吨结合饱和度进行比较。[3H]匹氟噻吨对受体的占据与多巴胺敏感腺苷酸环化酶的抑制之间存在线性关系。在第二个实验中，在与[3H]匹氟噻吨进行初始孵育时加入多巴胺。这导致特异性[3H]匹氟噻吨结合被取代，结果是[3H]匹氟噻吨对多巴胺敏感腺苷酸环化酶的抑制作用降低。在初始孵育中不存在GTP时，多巴胺对[3H]匹氟噻吨对多巴胺腺苷酸环化酶抑制作用的降低幅度大于对特异性[3H]匹氟噻吨结合的取代。在初始孵育中存在GTP时，两条取代曲线均向右移动，即多巴胺的效力降低。然而，在这些条件下，多巴胺对[3H]匹氟噻吨对多巴胺腺苷酸环化酶抑制作用的抑制幅度小于对特异性[3H]匹氟噻吨结合的取代。这些结果被解释为是由于在存在或不存在GTP的情况下孵育导致D-1高和D-1低比例发生变化所致。
