Signal Transduction by Dopamine D1 Receptors

In vertebrates the D1 family of dopamine receptors comprises at least three members, coded by different genes: D1a (or D1), D1b (or D5), and D1c/d (Vernier et al. 1995). However, only D1 and D5 have been identified in mammals. These receptors are characterized by their high degree of sequence identity and their common ability to interact with Gs-like proteins and to stimulate adenylyl cyclase. Most of our knowledge of the signaling by these receptors has been gained by studying the D1a isoform, by far the most abundant in brain, especially in striatonigral medium-size spiny neurons.