Body size and brain volumetry in the rat following prolonged morphine administration in infancy and adulthood.

Background: Prolonged morphine treatment in infancy is associated with a high incidence of opioid tolerance and dependence, but our knowledge of the long-term consequences of this treatment is sparse. Using a rodent model, we examined the (1) short- and (2) long-term effects of prolonged morphine administration in infancy on body weight and brain volume, and (3) we evaluated if subsequent dosing in adulthood poses an increased brain vulnerability.

Methods: Newborn rats received subcutaneous injections of either morphine or equal volume of saline twice daily for the first two weeks of life.