In this review, we will provide further support for the idea that cholinergic neurotransmission in the brain is primarily neuromodulatory and is categorically distinct from the actions of ACh at the neuromuscular junction. We propose that the role of ACh as a neuromodulator in the brain is to increase neurotransmitter release in response to other inputs, to promote burst firing and/or suppress tonic firing, depending upon the system and the neuronal subtypes stimulated. Further, ACh contributes to synaptic plasticity in many brain areas.
