Neurotransmitters in the brain of most relevance to addiction

Many different neurotransmitters exist within the central nervous system (CNS), each binding to specific receptor types, which have distinct distributions and roles.^[1,3,4] The variety of neurotransmitters within the CNS contributes to the functional complexity of the brain.^[1] Different neurotransmitters can produce different responses on the same neuron; e.g., a neuron might be excited by the binding of serotonin, but inhibited by the binding of GABA.^[1]

References:
[1] Purves D, Augustine GJ, Fitzpatrick D, et al. (eds). Neuroscience. 6th edition. Sunderland, MA: Sinauer Associates, Inc. 2018.

[2] Brunton LL, Lazo JS, Parker KL (eds). Goodman & Gilman’s The Pharmacological Basis of Therapeutics. 11th edition. McGraw-Hill, 2006.

[3] Stahl SM. Stahl’s Essential Psychopharmacology. Neuroscientific Basis and Practical Applications. 4th edition. © Cambridge University Press, 2013.

[4] Kandel ER, Schwartz JH, Jessell TM (eds). Principles of Neural Science. 4th edition. McGraw-Hill, 2000.