4-Aminopyridine is a non‑selective K⁺ channel blocker. 4-Aminopyridine blocks voltage‑gated potassium currents in axons, thereby prolonging action potential duration and facilitating neurotransmitter release. 4-Aminopyridine also possesses broad‑spectrum anti‑inflammatory and neuroprotective activities in vitro and in vivo. 4-Aminopyridine is a potential drug for Alzheimer's disease (AD), and 4‑aminopyridine has demonstrated therapeutic benefits in Lambert‑Eaton syndrome and myasthenia gravis as well[1][2][3].
In vitro, 4-Aminopyridine (130μM) induces a transient elevation in miniature end‑plate potential (mEPP) frequency in frog skeletal muscle fibers, persisting for about 1 hour, while exerting no effect on either the amplitude or frequency of mEPPs in rat muscle fibers[2]. 4-Aminopyridine (0–128μM) dose-dependently increases the amplitude of endplate potentials (EPPs) in rat muscle[2]. In D-Tubocurarine‑blocked rat muscles, 4‑AP (130μM) enhanced endplate potential (EPP) amplitude during repetitive stimulation at 1 and 10Hz, whereas this potentiation was diminished at higher stimulation frequencies (50 and 100Hz)[2]. 4-Aminopyridine (2mM; 48h) significantly decreases Aβ1–42‑induced neurotoxicity in microglial cells, with a reduction of 54%[1]. 4-Aminopyridine (100μM; 10min) increased neuronal activity in 90-day-old cerebral spheroids[6].
In vivo, 4-Aminopyridine (1mg/kg/d; i.p.; 7 days) attenuates the neurotoxic effects of Aβ1–42 and effectively protects neurons from Aβ1–42‑induced damage in Sprague‑Dawley rats[1]. Intraperitoneal administration of 4-Aminopyridine (13mg/kg) in mice caused seizures, with a mean latency to seizure onset of 11.4min and a mortality rate of 100%[4]. Single-dose 4-Aminopyridine (5mg/kg; i.p.) induced acute generalized brain hypometabolism in rats, sparing the cerebellum, at 5-10min post‑injection[5].
References:
[1] Franciosi S, Ryu JK, Choi HB, Radov L, Kim SU, McLarnon JG. Broad-spectrum effects of 4-aminopyridine to modulate amyloid beta1-42-induced cell signaling and functional responses in human microglia. J Neurosci. 2006;26(45):11652-11664.
[2] Lundh H. Effects of 4-aminopyridine on neuromuscular transmission. Brain Res. 1978;153(2):307-318.
[3] Sherratt RM, Bostock H, Sears TA. Effects of 4-aminopyridine on normal and demyelinated mammalian nerve fibres. Nature.
[4] Li M, Kang R, Shi J, Liu G, Zhang J. Anticonvulsant activity of B2, an adenosine analog, on chemical convulsant-induced seizures. PLoS One. 2013;8(6):e67060.
[5] Gómez-Oliver F, Fernández de la Rosa R, Brackhan M, Bascuñana P, Pozo MÁ, García-García L. Seizures Triggered by Systemic Administration of 4-Aminopyridine in Rats Lead to Acute Brain Glucose Hypometabolism, as Assessed by [18F]FDG PET Neuroimaging. Int J Mol Sci. 2024;25(23):12774.
[6] Parmentier T, James FMK, Hewitson E, et al. Human cerebral spheroids undergo 4-aminopyridine-induced, activity associated changes in cellular composition and microrna expression. Sci Rep. 2022;12(1):9143.