Figure 2. Working model of changes in nAChR functions in the brain associated with nicotine addiction.
Chronic exposure to nicotine upregulates the stimulatory α7nAChR without concomittant receptor desensitization, whereas the inhibitory α4β2nAChR undergoes long-term desensitization accompanied by upregulation. The resulting predominance of excitatory neurotransmitters and relative deficiency in inhibitory GABA lead to symptoms associated with nicotine addiction and craving.
GABA-B-R: GABA-B receptor; GPCR: G-protein-coupled receptor; nAChR: Nicotinic acetylcholine receptor.