Ventral ve Dorsal Kök Aksonları Üzerine 4-Aminopiridinin Farklı Etkileri

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