| It is possible to breastfeed an adopted baby. Lactation is controlled by prolactin (which makes the milk) and oxytocin (which releases it), which are pituitary and not ovarian hormones: even a woman who has had a hysterectomy may lactate, though the form of estrogen typically given after such a procedure - the same form found in birth control pills - is a lactation suppressant.
MizerieRose's sucking method works because prolactin and oxytocin are produced in response to nipple stimulation; a baby or a breast pump will work equally well in this. It will typically take one to four weeks for human or mechanical stimulation to induce lactation.
Hormonal therapy can also be used, including estrogen administered in a way to trick the body into thinking it is pregnant. Estrogen is then withdrawn, mimicking the rapid hormonal changes following delivery. A drug such as metaclopromide is then given to enhance prolactin production, and sucking stimulation is also used at this point. This method usually begins to produce milk after five to thirteen days.
There are also natural methods that can be used to help induce lactation. Fenugreek and blessed thistle can sometimes be found in health food stores or other locations with a good selection of herbal supplements. Domperidone, a drug given for gastric problems, has a side effect of increasing lactation.
Sources:
http://www.surrogacy.com/medres/article/lac.html
http://www.submission.net/lactation.html
http://www.adoptivebreastfeeding.com/ | 
