Final answer:
M2 and M4 inhibitory receptors are part of the G-protein-coupled receptor family and are coupled to Gi and Go proteins. When activated, these receptors inhibit the activity of adenylate cyclase and decrease cellular activity.
Step-by-step explanation:
M2 and M4 are inhibitory receptors that are part of the G-protein-coupled receptor (GPCR) family. These receptors are coupled to Gi and Go proteins. When these receptors are activated by ligands, such as neurotransmitters, they inhibit the activity of adenylate cyclase, leading to a decrease in the production of cyclic adenosine monophosphate (cAMP) and a subsequent decrease in cellular activity.
For example, when the M2 receptor is activated, it inhibits the activity of adenylate cyclase and reduces the heart rate. On the other hand, when the M4 receptor is activated, it inhibits neurotransmitter release in the brain and can have effects on cognition and behavior.
Overall, M2 and M4 inhibitory receptors, coupled to Gi and Go proteins, play important roles in regulating cellular activity by inhibiting signaling pathways that involve cAMP.