| The cholinergic projection from nucleus basalis to neocortex is implicated in behaviors such as arousal, attention, learning, memory, sensory perception and motor control. Dysfunction or elimination of this input results in deficits in these behaviors and has been tied to pathophysiological conditions such as Alzheimer's disease. I studied the cellular effects of acetylcholine release in cortical pyramidal neurons. I show that cortical pyramidal neurons respond to release of acetylcholine via both muscarinic and nicotinic receptors. Activation of nicotinic receptors increased pyramidal neuron excitability either transiently or persistently depending upon the resting membrane potential of the neuron, suggesting that the time course of nicotinic receptor-mediated modulation might be dictated by the behavioral state of the animal. Nicotinic receptor-mediated depolarizations were present in all cortical layers and in many cortical regions, however there were local variations in both the probability and amplitude of nicotinic receptor-mediated depolarizations in different layers of different cortical regions. The laminar pattern of nicotinic receptor modulation was unique to each cortical region studied, suggesting that nicotinic receptors function to alter the balance of cortical subcircuits and that the manner of network modulation is specific to different cortical regions. |
