Chunk #21 — Identifying Specific Genes Related to AOD Dependence — Genes Encoding Proteins Involved in Neurotransmission — Genes Involved in the Cholinergic System
The cholinergic system includes neurons that either release the neurotransmitter acetylcholine or respond to it. Acetylcholine generally has excitatory effects in the human central nervous system—that is, it affects neurons in a way that enhances their activity. It is thought to be involved in such processes as arousal, reward, learning, and short-term memory. One of the receptors through which acetylcholine acts is encoded by a gene called CHRM2. In the COGA sample, linkage was observed between a region on chromosome 7 that contains the CHRM2 gene and alcohol dependence, and subsequent experiments confirmed that an association existed between alcohol dependence and the CHRM2 gene (Wang et al. 2004). This association has been replicated in a large independent study (Luo et al. 2005) that also found evidence that the gene was associated with drug dependence.
