In Vivo Voltametri ile Nörotransmitter Ölçümleri
Özet
Merkezi Sinir Sistemi'ndeki nörotransmitterlerin dinamiklerini yaşayan canlıda yüksek özgünlük ve seçicilikle saniye temelinde ölçebilen "in vivo voltametri" tekniği, beyin hastalıklarının araştırılmasında kritik bir öneme sahiptir. Geleneksel mikrodiyaliz yöntemi dakika bazında ölçüm yapabilirken ve dokuda hasar bırakabilirken; in vivo voltametri, milisaniyeler düzeyinde hızlı kayıt alabilmekte ve dokuya zarar vermemektedir. Sistem, bilgisayar kontrollü mikroelektrotlar aracılığıyla elektroaktif moleküllerin oksitlenmesi veya indirgenmesi sonucu oluşan Faradaik akımları ölçer. Ölçümü istenmeyen askorbik asit gibi girişim yapan maddeleri engellemek için elektrotlar Nafiyon veya 1,3 fenilendiamin gibi seçici bariyerlerle kaplanır; elektroaktif olmayan glutamat gibi maddelerin tespiti için ise özel oksidaz enzimleri kullanılır. Deney öncesinde 37°C'de in vitro kalibrasyon yapılarak elektrotların hassasiyeti ve seçiciliği test edilir. Lokal ilaç uygulamaları için entegre edilen cam mikropipetler ve kimyasal gürültüyü dışlayan "öz-referans" sistemi sayesinde net ölçümler elde edilir. Anestezi altındaki hayvanlarda başarıyla uygulanan ve kronik implantasyonda belirgin bir histopatolojik hasara yol açmadığı kanıtlanan bu teknoloji, Parkinson, epilepsi ve şizofreni gibi birçok beyin hastalığının mekanizmasını anlamada ve nörotransmitter kinetiklerini takip etmede güçlü bir yöntem sunmaktadır.
The "in vivo voltammetry" technique, which can measure the dynamics of neurotransmitters in the Central Nervous System in living organisms on a second basis with high specificity and selectivity, is of critical importance in the research of brain diseases. While the traditional microdialysis method can perform measurements on a minute basis and may leave damage in the tissue, in vivo voltammetry can record rapidly at millisecond levels and does not harm the tissue. The system measures Faradaic currents resulting from the oxidation or reduction of electroactive molecules through computer-controlled microelectrodes. To prevent interfering substances whose measurement is not desired, such as ascorbic acid, electrodes are coated with selective barriers like Nafion or 1,3-phenylenediamine; meanwhile, specific oxidase enzymes are used for the detection of non-electroactive substances such as glutamate. Prior to the experiment, in vitro calibration is performed at 37°C to test the sensitivity and selectivity of the electrodes. Clear measurements are obtained thanks to glass micropipettes integrated for local drug applications and the "self-referencing" system that excludes chemical noise. Successfully applied in anesthetized animals and proven not to cause significant histopathological damage in chronic implantation, this technology offers a powerful method in understanding the mechanism of many brain diseases such as Parkinson's, epilepsy, and schizophrenia, and in monitoring neurotransmitter kinetics.
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