Dopamine neurons and synapse. Representation of the connection between two dopamine neurons at the synapse to pass the message (nerve impulse from one neuron to another) and zoom on the synapse. Here they are dopamine neurons (reward system of the brain). Excitatory neurotransmitters (acetylcholine) that can bind to multiple types of receptors located at different locations on neurons are reported to increase the electrical activity of dopamine neurons in the reward system. Since nicotine receptors are subclasses of acetylcholine receptors, they also increase the electrical activity of dopamine neurons in the reward system. (Pleasure felt when smoking a cigarette).