Brain beta-endorphin-like immunoreactivity in adult rats given beta-endorphin neonatally.
beta-endorphin-like immunoreactivity was measured by radioimmunoassay in the brains of adult rats treated neonatally with beta-endorphin, naloxone, or vehicle. After treatment with beta-endorphin, the decreases observed in beta-endorphin-like immunoreactivity in the hypothalamus, pineal, midbrain, pons-medulla, hippocampus, striatum, frontal cortex, occipital cortex, and posterior cortex were highly significant but the 23% decrease in the thalamus was not significantly different from that of control rats. Neonatal administration of naloxone only resulted in a significant decrease in beta-endorphin-like immunoreactivity in the hypothalamus. In contrast, no differences were discernible in content of either beta-endorphin-like immunoreactivity or ACTH-like immunoreactivity in the pituitary of rats treated with beta-endorphin, naloxone, or vehicle in the neonatal period. These same rats had shown an increased threshold to painful thermal stimulation by the tail-flick test after administration of either beta-endorphin or naloxone at birth. The results suggest that neonatally injected beta-endorphin may alter the levels of beta-endorphin-like immunoreactivity in rat brain as well as the response to pain.
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects*; D004723:Endorphins / Q000032:analysis / Q000494:pharmacology*; D005260:Female; D009270:Naloxone / Q000494:pharmacology; D010902:Pituitary Gland / Q000032:analysis; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011863:Radioimmunoassay; D051381:Rats; D001615:beta-Endorphin
D004723:Endorphins; D009270:Naloxone; D001615:beta-Endorphin