Rabbit P300-like potential depends on cortical muscarinic receptor activation

Novel stimuli trigger a positive brain potential P300 or P3a in mammalian animals, which is considered to represent an orienting response. Drugs systemically administered showed that acetylcholine is involved in the generation of P3. However, it is not known in which structure acetylcholine interacts with other neuronal substances for P3 generation. In this study, we injected scopolamine, an acetylcholine antagonist, into the parietal cortex. After the injection the amplitude of P3 from the parietal electrode decreased, while P3 recorded from neighbouring cortex was preserved. The peak latency of it did not show any significant change after the injection. P3 did not show any significant change after injecting normal saline into the same area. The parietal cortex is an essential structure for local P3 generation Different cerebral cortical regions respond to novel stimuli in parallel, and muscarinic receptor activation is necessary for processing the information of novelty detection.