D2 (DRD2). There is a short version of D2 (D2Sh) and a long version of D2 (D2Lh): The D2Sh are pre-synaptic situated, having modulatory functions (called autoreceptor, they regulate the neurotransmission by feed-back mechanisms, i.e., synthesis, storage and release of dopamine into the synaptic cleft).

The D2Lh may have the classic function of a post-synaptic receptor, i.e., keep going on the neurotransmission (excitatory or inhibitory) once blocked by a receptor antagonist or stimulated by the endogenous neurotransmitter itself or a synthetic full or partial agonist.D2-like activation is coupled to the G protein Gαi, which subsequently increases phosphodiesterase activity. Phosphodiesterases break down cAMP, producing an inhibitory effect in neurons.