Figure 1. Regulatory functions of the α7nAChR and the α4β2nAChR in the brain.
The α7nAChR acts as an ‘accelerator by stimulating the synthesis and release of the excitatory neurotransmitters noradrenaline (from which adrenaline is formed), dopamine, glutamate and serotonin. Most effects of these neurotransmitters are mediated by GPCRs that activate the enzyme anenylyl cyclase. The α4β2nAChR acts as the ‘brake’ by stimulating the synthesis and release of the inhibitory neurotransmitter GABA, which blocks GPCR-mediated activation of adenylyl cyclase by Gi-mediated activity of the GABA-B-R.
GABA-B-R: GABA-B receptor; GPCR: G-protein-coupled receptor; nAChR: Nicotinic acetylcholine receptor.