Effect of drugs on the spike complication of hippocampal field potentials

Drugs were applied to the alvear surface of the dorsal hippocampus with pieces of filter paper soaked in suitable solutions, and their effect on the hippocampal spike complication was examined. The size of the spike complication, for a given stimulus strength, was decreased by procaine and tetrodotoxin, and increased by aconitine. When stimuli below threshold for the spike complication were used, a short number of pulses at a 10 per sec rate caused this potential to appear; this number of pulses was increased by procaine, tetrodotoxin and tetraethylammonium, and decreased by aconitine and veratrine. These results suggest that spike complications are the envelopes of Na⁺ spikes, and that an accumulation of extracellular K⁺ favors their appearance.