中枢5－HT_（1A）受体在大鼠脑中的不同亲和力状态

Different affinity states of the 5-HT_(1A) receptor in rat brain

用特异性配体［~３Ｈ］８－ＯＨ－ＤＰＡＴ与大鼠脑中不同部位脑组织膜制剂的５－ＨＴ_（１Ａ）受体结合，显示出在海马、延髓、下丘脑的最大结合容量和亲和力有明显不同。各种孵育缓冲液使鼠脑海马、延髓膜制剂与［~３Ｈ］８－ＯＨ－ＤＰＡＴ的结合呈现不同的亲和力状态。孵育缓冲液中加入Ｍｎ^（２＋）和Ｇｐｐ（ＮＨ）_ｐ或均不加时，结合呈高、低两种亲和力状态；而仅加入Ｍｎ^（２＋）或同时加入ＥＤＴＡ和Ｇｐｐ（ＮＨ）_ｐ时，结合分别呈单一的高、低两种亲和力状态。５－ＨＴ_（１Ａ）受体激动剂和拮抗剂的竞争实验结果也表明：５－ＨＴ_（１Ａ）受体至少存在两种不同亲和力的状态。

Further evidence for differential affinity states of the serotonin receptor in rat brain is provided. The specific binding of [~3H]8-OH-DPAT to 5-HT_(1A) receptor related site was investigated in the preparation of several brain regions. Significant differences in the B_(max) and K_d were observed in the characteristic of binding to membranes from hippocampus, medulla oblongata and hypothalamus. With the different buffer solution, the specific binding displayed various affinity states in various membrane preparations. Two affinity states were shown in the presence or absence of both Mn￣(2+) and Gpp(NH)p in the incubation buffer. In contrast to the two affinity states,a single high affinity state was observed in the presence of Mn￣(2+) in the buffer, while a single low affinity state was observed with the elimination of Mn￣(2+) from the buffer and adding of both the 100 μmol/L Gpp(NH)p and 1.0 mmol/L EDTA to the incubation buffer. Competitiors of the [￣3H]8-OH-DPAT binding site, such as serotonin and unlabelled 8-OH-DPAT also showed two affinity states while other like spiperone showed single low affinity state. These results suggest that the 5-HT_(1A) binding site may exhibit at least two different affinity states.