Answer:
G protein - coupled receptors(GPCRs)n belong to a large family of signaling proteins that mediate cellular reponses to most hormones ,metabolites,cytokines and neuotransmitters and therefore serve as fritful targets for DRUGS DISCOVERYS.
Explanation: histamine(HRH1),serotonin dopamine,opiod and adrenergic receptors.
I HOPE IT'S HELPS YOU TO UNDERSTAND
