Which G protein is linked to alpha2 receptors?

Alpha2 adrenergic receptors are primarily linked to the Gi family of G proteins. When these receptors are activated by catecholamines like norepinephrine, they undergo a conformational change that allows them to interact with the Gi protein. This interaction decreases the production of cyclic AMP (cAMP) within the cell by inhibiting adenylate cyclase.

The reduction of cAMP levels leads to various physiological effects, including decreased neurotransmitter release in the sympathetic nervous system. This is in contrast to alpha1 receptors, which are linked to Gq proteins and promote the activation of phospholipase C, and beta receptors, which are coupled to Gs proteins that increase cAMP levels.

Overall, the association of alpha2 receptors with the Gi protein is crucial for their role in mediating inhibitory signals, which is characteristic of these adrenergic receptors in the context of autonomic regulation.