Effects of intracellularly applied aminopyridine on firing activities and synaptic responses of electrophysiologically identified cell types in the motor cortex of cats.

Effects of 3-aminopyridine (3-Ap) applied intracellularly into electrophysiologically identified cortical neurons in the cat motor cortex were studied. Actions on the membrane and firing activity properties, excitatory and inhibitory postsynaptic responses were investigated. Intracellular microelectrode techniques and single electrode voltage clamp methods were used in experiments on anesthetized and chronic nonanesthetized cats. In addition to changes in neuronal excitability and firing activity properties the evoked postsynaptic responses were significantly altered. Augmentation of EPSPs was accompanied by increases of the total duration and amplitude of the second slow component of IPSPs without influencing the early fast IPSP component. It is concluded that most actions of 3-Ap reported here are derived from direct effects of 3-Ap on the postsynaptic membrane.