Increased opioid release in specific brain areas in animals exposed to prenatal morphine and emotional stress later in life

Prenatal morphine treatment and emotional stress both have been shown to increase sensitivity to reward-related behaviors. It has been postulated that this increased sensitivity to rewarding stimuli may be the result of an enhanced release of endogenous opioids. In the present study, in vivo autoradiography was employed to investigate the endogenous opioid release in specific brain areas in rats. Pregnant animals were exposed to morphine or saline from day 8 of gestation till birth. Development of pups was monitored and play behavior was tested on postnatal day 21. Adult rats were exposed to repeated emotional stress or control treatment for five consecutive days and tested in a small open field 5 days later. [³H]-Diprenorphine was injected following this test to investigate endogenous opioid release.