以微型化多孔道玻璃電極探討愷他命對於大鼠視丘觸覺神經元之影響

Abstract

過去二十年以來，我們實驗室致力於研究大鼠觸覺與痛覺神經訊號的傳遞，而這些基礎研究讓我們萌發探討藥物如愷他命對於這兩條神經路徑傳導有何影響的想法。為了達到這個目的，我們必須同時紀錄大鼠皮質與視丘之神經訊號，並在此兩腦區給予定量藥物注射。然而，當今的壓力注射藥物系統大多十分龐大，加上大鼠大腦空間有限，因此儀器的架設限制住此實驗的可行性。 為了解決這個挑戰，在這篇論文中提供一簡單的方法製造出一微電極不但能紀錄神經訊號，還能注射定量藥物於紀錄腦區中。由於此微電極所佔實驗空間很小，故能解決上述之問題。此外，我們利用此電極探討愷他命對於大鼠視丘觸覺神經元的影響，期盼不只能驗證此微電極能否應用至動物實驗中，也能一窺愷他命對於視丘觸覺神經元的直接影響。 由實驗結果，我們觀察到在注射兩次定量的愷他命後，神經活性等比例的抑制，證明了此電極的可行性。而在神經恢復期間，神經活性呈現不規則的活性變化，並且，愷他命對於觸覺神經元的抑制效果也不盡相同。因此，我們認為這些現象或許能夠解釋為什麼愷他命吸食者會產生幻覺以及與現實脫離的感覺。

In our lab, we have dedicated to investigate signal transmissions of the touch and nociception for more than two decades. Now, the agent effects on these two signal pathways are needed to be explored. However, since pressure-injection systems commercially available are bulky and expensive, it is hardly possible to construct recording-injection microelectrode with multiple channels at multisite to both record neuronal responses and to deliver agents in the brain of a small animal, such as the rat. To overcome this challenge, an innovative miniaturized recording-injection microelectrode was constructed in this thesis. The injection system was built by sealing a tapped polyethylene tube, connected with a Hamilton syringe, into one barrel of the microelectrode with super glue, so the proposed electrode can save much operational space in animal experiences. Our results also support that it is reliable to inject quantitative drugs. First, the r-squared of the calibration line between the output volume of the syringe and the really ejected volume reached 0.99. Secondly, the numbers of the evoked action potentials of rat thalamic tactile neurons were decreased proportionally after the injection of two times same amount of ketamine. Besides that, we observed the differential inhibitory effect of ketamine on these neurons and the fluctuations of neuronal activities during the recovery. These phenomena might partially explain the dissociative effect of ketamine and the ketamine-induced hallucination but the further researches are still required to uncovering the underlying mechanism of these interesting situations. In conclusion, the miniature recording-injection microelectrode was proved to be a reliable tool to conduct more delicate neuropharmacological studies in small animals. After all, the proportional inhibitory local effect of ketamine on rat thalamic tactile neurons was directly demonstrated.