title: Development of cerebral methionine-enkephalinergic neurons in rats: some difference in Wistar-Kyoto rats and spontaneously hypertensive rats.
abstract: Development of methionine-enkephalin (ME) and ME receptor binding in the embryonic and neonatal rat cerebral nuclei was defined quantitatively by immunocytofluorescent and microautoradiographic methods. On embryonic days 14 and 18, ME was localized in 10 of 83 nuclei particularly in the n. amygdaloideus centralis, n. periventricularis, n. supraopticus, n. interpeduncularis, n. suprachiasmaticus, n. arcuatus and n. ambiguus. ME receptor binding was distributed in the former 4 nuclei on embryonic day 14 and additional 5 nuclei on embryonic day 18. At the day of birth both levels markedly increased in these nuclei (2-3 times) and abruptly emerged in 65 out of 73 nuclei in which ME neurons were not detectable in embryonic nuclei. The abrupt appearance in most nuclei at birth probably regulates nociceptive and non-nociceptive stimuli at birth and in the neonatal period. Both levels attained their maximum at the postnatal day 7 and gradually declined thereafter. Among the perinatal period examined, ME immunoreactivity in the tractus spinalis nervi trigemini and ME receptor binding in the n. tractus spinalis nervi trigemini were markedly lower in both SHR neonates than in corresponding Wistar-Kyoto rats. Lowered levels in both areas of neonatal SHR may be involved in central hyperreactivity and preganglionic sympathetic activation of young SHR.
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000196:embryology / Q000254:growth & development* / Q000502:physiology; D004744:Enkephalin, Methionine / Q000378:metabolism*; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011922:Rats, Mutant Strains; D011957:Receptors, Opioid / Q000502:physiology*; D013045:Species Specificity; D014018:Tissue Distribution
chemical_list: D011957:Receptors, Opioid; D004744:Enkephalin, Methionine