Could you tell me what hormones counteract oxytocin and how do they do it?

Why?: Not sure why you are asking this. Oxytocin is the hormone released by the pituitary gland during breast feeding that causes release of milk. It is also used pharmacologically to induce labor as it causes uterine contraction. If your question is more related to stopping breast milk production after pregnancy, bromocriptine had been used previously, but is no longer allowed for this use.