text: One of the first DREADDs was based on the human M muscarinic receptor (hM). Only two point mutations of hM were required to achieve a mutant receptor with nanomolar potency for CNO, insensitivity to acetylcholine and low constitutive activity and this DREADD receptor was named hM3Dq. M and M muscarinic receptors have been mutated to create DREADDs hM1Dq and hM5Dq respectively. 
  The most commonly used inhibitory DREADD is hM4Di, derived from the M muscarinic receptor that couples with the G protein. Another G coupled human muscarinic receptor, M, was also mutated to obtain the DREADD receptor hM2D. Another inhibitory G-DREADD is the kappa-opioid-receptor (KOR) DREADD (KORD) which is selectively activated by salvinorin B (SalB).
  G-coupled DREADDs have also been developed. These receptors are also known as GD and are chimeric receptors containing intracellular regions of the turkey erythrocyte β-adrenergic receptor substituted into the rat M DREADD.