Raghupathi R K, Artymyshyn R, McGonigle P
Department of Pharmacology, University of Pennsylvania, Philadelphia 19104, USA.
Brain Res Mol Brain Res. 1996 Jul;39(1-2):198-206. doi: 10.1016/0169-328x(96)00024-1.
In this study, the relationship between the expression of 5-HT2A receptors and level of 5-HT2A receptor mRNA in discrete regions of rat brain was examined by inactivating 5-HT2A receptors with the alkylating agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ; 10 mg/kg, i.p.) and measuring the time course of receptor recovery and changes in mRNA levels. In untreated controls, the distribution and levels of 5-HT2A receptors labeled with [3H]ketanserin and receptor mRNA labeled with a 230-base 33P-labeled riboprobe were found to be highly correlated in most sub-regions of the cortex, the caudate-putamen and the claustrum but not in the piriform cortex or the hippocampus. Administration of EEDQ produced 90-99% inactivation of 5-HT2A receptors and the rate of receptor recovery was uniform in most regions studied. 5-HT2A receptors in most regions reached control levels by day 14, the lone exception being the caudate-putamen where receptors reached only 56% of control by day 14. Following inactivation of receptors with EEDQ there was a transient increase in levels of 5-HT2A receptor mRNA in several regions. Although rates of receptor recovery were uniform, four distinct patterns of mRNA response were observed: (1) early elevation followed by late elevation, (2) early elevation only, (3) late elevation only, and (4) no detectable change. The absence of a direct relationship between changes in 5-HT2A receptor mRNA and 5-HT2A receptor recovery in this model system suggests that transcriptional regulation is not the mechanism controlling the recovery of these receptors after irreversible inactivation. This study also lends support to the idea that alternative mechanisms may play a role in 5-HT2A receptor regulation after other pharmacological and physiological manipulations. The regional variability in 5-HT2A mRNA regulation reported here highlights the importance of using techniques with a high level of anatomical resolution to study changes in 5-HT2A receptor mRNA levels.
在本研究中，通过用烷基化剂N - 乙氧羰基 - 2 - 乙氧基 - 1,2 - 二氢喹啉（EEDQ；10 mg/kg，腹腔注射）使5 - HT2A受体失活，并测量受体恢复的时间进程和mRNA水平的变化，研究了大鼠脑离散区域中5 - HT2A受体表达与5 - HT2A受体mRNA水平之间的关系。在未处理的对照组中，发现用[3H]酮色林标记的5 - HT2A受体的分布和水平与用230个碱基的33P标记的核糖探针标记的受体mRNA在皮质、尾状核 - 壳核和屏状核的大多数亚区域中高度相关，但在梨状皮质或海马中则不然。给予EEDQ导致5 - HT2A受体90 - 99%失活，并且在大多数研究区域中受体恢复速率是一致的。大多数区域的5 - HT2A受体在第14天达到对照水平，唯一的例外是尾状核 - 壳核，其中受体在第14天仅达到对照的56%。在用EEDQ使受体失活后，几个区域中5 - HT2A受体mRNA水平出现短暂升高。尽管受体恢复速率是一致的，但观察到四种不同的mRNA反应模式：（1）早期升高后晚期升高，（2）仅早期升高，（3）仅晚期升高，以及（4）无可检测到的变化。在该模型系统中5 - HT2A受体mRNA变化与5 - HT2A受体恢复之间不存在直接关系，这表明转录调节不是控制这些受体在不可逆失活后恢复的机制。本研究还支持这样一种观点，即替代机制可能在其他药理和生理操作后5 - HT2A受体调节中起作用。此处报道的5 - HT2A mRNA调节的区域变异性突出了使用具有高解剖分辨率的技术来研究5 - HT2A受体mRNA水平变化的重要性。
