Effects of iontophoretic administration of acetylcholine to rabbit motor cortex neurons on the functioning of intracortical connections.

Experiments were performed on eight rabbits to study the effects of acetylcholine on interneuronal intracortical interactions. Multineuronal activity was recorded in the motor cortex during local iontophoretic administration of acetylcholine and physiological saline. Interneuronal connections were identified by cross-correlation analysis. A role for acetylcholine in intracortical connection reorganization processes is proposed. These studies demonstrated that acetylcholine has an activating effect on intracortical connections; application of acetylcholine leads to increases in the intensity of short-latency, constantly functioning (stable) connections. Acetylcholine application also resulted in the formation of unstable, long-latency connections. Additionally, the data suggest that iontophoretic application of acetylcholine does not lead to the formation of new short-latency interneuronal connections. The modulatory effects of acetylcholine on the network activity of cortical neurons are discussed.