Ventral ve Dorsal Kök Aksonları Üzerine 4-Aminopiridinin Farklı Etkileri

Year 2014, Volume: 5 Issue: 20, 11 - 19, 03.03.2015

İbrahim Kahraman , Mustafa Güven Fatih Sefil Recep Dokuyucu , İsmail Günay

https://doi.org/10.17944/mkutfd.61029

Abstract

Amaç: Motor ve Duysal sinir lifleri bir potasyum kanal blokörü olan 4-Aminopiridine karşı (4-AP) farklı yanıt verebilirler. Bu çalışmadaki amacımız sıçan ventral ve dorsal arka kök aksonlarının elektrofizyolojik özelliklerini 4-AP ve Birleşik Sinir Aksiyon Potansiyelleri (BSAP) aracılığı ile araştırmaktır.
Materyal-Metod: Wistar türü erkek sıçanlar ether anestezisi altında karotoid arter kesisi ile hızlı bir şekilde sakrifiye edildi. Lumbar (L-4) ventral ve dorsal kök aksonları laminektomi yöntemi ile hızlıca çıkarılıp 95% 02+5% CO2 ile gazlandırılan soğuk Krebs içine alındı. 4-AP etkisini değerlendirmek için BSAP kayıtları modifiye sukroz-gap aparatı ile in vitro olarak ölçüldü. Tüm deneyler 20-22 oC yürütüldü.
Bulgular: Ventral köklerden kayıtlanan BSAP toplam süresi 4-AP uygulaması ile uzadı ve dinlenim değerine dönmesi gecikti. Dorsal köklerde ise toplam BSAP süresi ventral köklere göre en az iki kat daha fazla uzadı. Ayrıca dorsal köklerde 4-AP sonrası dinlenim değerine dönerken belirgin bir hump (hörgüç) gözlendi. Bu fenomen ventral köklerde görülmedi. Ventral ve dorsal köklerden kayıtlanan BSAP latansları sırasıyla 256 ± 24 ve 508 ± 69 μs, iletim hızı ise 20,4 ± 2,4 ve 10,8 ± 1,4 m/s olarak ölçüldü.
Sonuç: Bu çalışmada sıçan motor ve duysal aksonları üzerine 4-AP’nin çok farklı etkilere sahip olduğunu gösterdik. Motor ve duysal sinir lifleri üzerine 4-AP’nin farklı etkileri, bu sinirlerde bulunan miyelinli-myelinsiz akson oranlarının ve akson çaplarının farklı olmalarından kaynaklanabilir. İlave olarak ventral ve dorsal kök aksonlarında nod veya paranodda bulunan potasyum-sodyum kanal farklılığından kaynaklanabilir.

Keywords

Ventral-Dorsal Kök, Aksiyon Potansiyeli, 4-Aminopiridin, Sukrozgap

The Different Effects of 4-Aminophyridine on Ventral and Dorsal Root Axons

Abstract

Aim: Rat motor and sensory nerve fibers may responses differently to the potassium channelblocking agent, 4-aminopyridine (4-AP). In this study we examined the electrophysiological properties of rat ventral and dorsal root axons with 4-AP and compound action potentials (CAP’s). Materials-Methods: Male Wistar rats were sacrificed by rapid carotid exsanguinations’ under ether anesthesia. Lumbar (L-4) ventral and dorsal roots were excised with laminectomy and immediately placed in a modified chilly Krebs solution saturated with 95% 02, and 5% CO2. To evaluate effect of 4-AP on the roots, CAP’s were recorded in a modified sucrose gap chamber in vitro. All experiments were performed at 20-22 oC. Results: The total duration of CAP obtained from the ventral root was prolonged by 4-AP and the return to baseline was delayed. The duration of CAP of the dorsal root more broadened than ventral roots at least two fold. The CAP of the dorsal roots developed a distinct hump when return to baseline. This phenomenon was not observed in ventral roots. The latency of ventral and dorsal root were 256 ± 24 and 508 ± 69 µs, conduction velocity 20.4 ± 2.4 and 10.8 ± 1.4 m/s, respectively. Conclusion: In this study we showed that 4-AP has entirely different effects on rat motor and sensory axons. The differential effect of 4-AP on motor and sensory fibers may be due to differences in ratio of myelinated-unmyelinated axons and its diameters. In addition there may be differences node or paranode’s potassiumsodium channels diversity in ventral and dorsal roots

Keywords

Ventral-Dorsal Root, Action Potential, 4-Aminophyridine, Sucrose-gap

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