HTR6在癢覺搔抓行為中所扮演之角色

Abstract

在先前的研究中指出，透過血清素濃度的調節，能夠影響與傷害性感覺相關的行為及生理功能，然而血清素是如何調控癢覺訊號的傳遞至今仍尚未清楚。血清素的受體可分為許多種亞型，其中血清素受體亞型6型(HTR6)表現在背根神經節與脊椎背角，而此處與癢覺訊息傳遞有很大的關聯性。因此，在本研究之中，便是想探討HTR6是否參與了癢覺傳遞調控。為了理解HTR6是否參與了組織胺引發的癢覺訊號傳遞路徑，我們使用了搔抓行為實驗來檢測其癢覺程度在剔除HTR6 基因小鼠是否有所差異。結果表明，剃除HTR6基因的小鼠比起正常的小鼠，在皮下注射組織胺後有較為明顯的搔抓行為。這代表HTR6信號可能參與了抑制了組織胺引發的癢覺訊號傳導。除此之外，我們也檢測了HTR6是否也參與非組織胺引發的癢覺傳導路徑，在此實驗中，我們使用了氯奎寧做為非組織胺性的致癢源。然而結果顯示，HTR6可能僅作用於組織胺引發的癢覺傳遞路徑，因為剃除HTR6基因小鼠與正常小鼠，在皮下注射氯奎寧後搔抓行為實驗中並沒有顯著差異。

It has been shown in previous studies that serotonin could modulate behavioral and physiological functions of nociception by ascending or descending pathway, but how it regulates itch signal transduction is still unclear. There are several subfamilies of serotonin receptors and serotonin 6 receptor (HTR6) is expressed in dorsal root ganglion and dorsal spinal cord, which may involve in itch responses. Here I will investigate whether HTR6 is involved in the regulation of itch responses. To quantify my findings, I will evaluate the level of itch response in HTR knock-out by scratching behavior test. In this study, I found that the number of scratching bouts of HTR6 knock-out mice was significantly higher than wild-type mice after an intradermal injection of histamine. The results suggested that HTR6 signaling may play a role in inhibition of itch signal transduction. Moreover, HTR6-mediated itch response was likely to be a histamine-dependent effect since intradermal injection of chloroquine did not elicit alternation of scratching behavior between two genotypes.