How does brabantio react to the news, and why does he react in this manner? Is it understandable? Why is barabantio susceptible to iago's accusations?

Brabantio does not know what to think. He has been woken up in the middle of the night and told that "an old black ram. Is tupping your white ewe." Although Othello is a valuable commodity to Greece, Brabantio draws the line at the moor dating his daughter. Brabantio seeks out the Duke to complain. He has come to complain that Othello has bewitched his daughter Desdemona, he has seduced her into a relationship with him.

Brabantio: "Ay, to me.

She is abused, stol'n from me, and corrupted

By spells and medicines bought of mountebanks."

(Act 1 sc 3)