[Effect of scopolamine on the contents of beta-endorphin and oxytocin in hypothalamus, pituitary and plasma in morphine dependent rats].

Male Sprague-Dawley rats weighing 180-220 g were rendered dependent on morphine by repeated injections of morphine in increasing doses for 14 days. 0.3 mg/kg of scopolamine was injected intraperitoneally bid for 3 and 4 days. Control rats were similarly injected with saline. The contents of beta-endorphin (beta-EP) and oxytocin (OT) in hypothalamus, pituitary and plasma were measured by radioimmunoassay. The results showed that both beta-EP and OT in hypothalamus and plasma increased but both were decreased in pituitary in morphine dependent rats (P < 0.01). After scopolamine treatment, the contents of beta-EP increased but OT decreased in hypothalamus (P < 0.01), and both elevated significantly in pituitary (P < 0.01). The results suggested that scopolamine might modulate hypothalamus-pituitary system to affect the release or synthesis of beta-EP and OT in the brain.