CHRNB3 (Cholinergic Receptor Nicotinic Beta 3 Subunit) is a protein that constitutes part of the nicotinic acetylcholine receptor, which is crucial in cholinergic neurotransmission. Variations in the CHRNB3 gene have been associated with nicotine addiction and related behavioural traits, indicating its role in the brain’s addiction pathways and regulation of neural circuits.