[A novel ligand for chemogenetic receptors, Deschloroclozapine, enables rapid and selective modulation of neuronal activity and behavior in living animals]

A brain function is manifested by harmonizing some brain regions responsible for the function. Since pathological conditions in neuropsychiatric disorders are induced by the failure of this mechanism, it is crucial to identify the affected function by manipulating the specific brain regions. Designer receptors exclusively activated by designer drugs (DREADDs) are one of the chemogenetic tools that offer a means to repeatedly reversible control of the activity of a target neural population expressing a "designer receptor" by systemic injection of "designer drug," which is biologically inert. The most widely used DREADDs are muscarinic-based receptors, such as hM3Dq (excitatory) and hM4Di (inhibitory), which can be activated by clozapine-N-oxide (CNO). However, CNO has some concerns. First, because CNO has a modest brain penetrability, the effect is slow. Second, since CNO is metabolized to clozapine, an antipsychotic drug that acts on numerous endogenous receptors, the systemic administration may produce off-target actions. Therefore, we developed a new compound, deschloroclozapine (DCZ), to solve these issues. DCZ has a higher affinity and greater agonist potency than CNO with reduced off-target actions and can rapidly modulate the neuronal activity and behavior with muscarinic-based DREADDs in living animals. Given the potential weak point of CNO, DCZ affords clear benefits to many users of muscarinic-based DREADD, with increased reliability by removing concerns about possible off-target responses.