When molecule A and molecule B are added to the cells, Inositol Triphosphate level decrease. What is molecule b?

Question

context: when molecule A is added to the cells, increased levels of the 2nd messenger (inositol triphosphate (IP3) are detected. The receptor molecule A is binding to is Alpha 1 receptor and the first messenger is Epinephrine(adrenergic ligand). (I’m stumped what molecule b could be I’m thinking norepinephrine, but i do not know if when epi and NE are added to a cell IP3 decreases.)

‘also do you think the receptor site has a greater affinity for molecule A or B.

Answer 1

From how this question is worded (and the context provided), I think that molecule B could be a drug that blocks the receptor (an antagonist). Such drugs are called "alpha blockers," and there are many examples. Molecule A activates the receptor, which results in an increase in IP3. If molecule B is a drug that blocks the receptor, then the receptor will not be activated, and therefore IP3 will decrease. The receptor likely has a higher affinity for molecule B, because if it didn't, the receptor would remain active when both molecules were present (molecule A would be able to "overpower" molecule B, and the receptor would stay active.)