Synthalin hydrochloride is a K+ channel blocker with neuronal excitability modulating activity. Synthalin hydrochloride has an effect on NMDA-mediated depolarization, possibly through receptor-mediated modulation of L-glutamate and serotonin (5-HT). The use of Synthalin hydrochloride can enhance the understanding of changes in membrane potential of different neurons and help study the role of polyamines in neuronal excitability.