High levels of acetylcholine in the brains of mice can cause depression-like symptoms, states Dr. Marina Picciotto in Yale Scientific Magazine. In experiments with mice, researchers found that mice were less depressed in the presence of an acetylcholine blocker.
Most popular antidepressant medications block a neurotransmitter called serotonin, but 40 percent of individuals with depression do not react to these. As noted by Dr. Picciotto, acetylcholine levels can potentially be a determining factor for the occurrence of depression. In a study of individuals with depression, researchers discovered that people with chronic depression showed evidence of having higher concentrations of acetylcholine. Additionally, there is also a known connection between smoking and depression. The primary sensors for acetylcholine are called nicotinic receptors, which activate during smoking, creating a chemical imbalance.
Acetylcholine was the first neurotransmitter discovered, notes Kendra Cherry for About.com. It acts as a neuromodulator in the central nervous system where it plays a role in attention and arousal. In the peripheral nervous system, it is a major part of the autonomic nervous system, where it works to activate muscles. Neuromodulators act on a variety of neurons in the nervous system rather than working through the direct transmission between specific neurons.