Effects of neonatal treatment with Tyr-MIF-1, morphiceptin, and morphine on development, tail flick, and blood-brain barrier transport.
Morphine and endogenous peptides can alter developmental processes, inducing changes that can endure into adulthood. Morphiceptin binds to mu opiate receptors and to non-opiate sites labeled by Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2), an endogenous brain peptide known to modulate opiate effects. Morphine, morphiceptin, Tyr-MIF-1, morphine + Tyr-MIF-1, and morphiceptin+Tyr-MIF-1 (50 micrograms, s.c.) were given to rats during their first week of life. Animals given morphine alone or in combination with Tyr-MIF-1 had significantly lower body weights for the first 3 weeks of life and delayed eye opening on day 16. Rats given morphine had hypersensitive tail flick responses on day 9 while those given morphine + Tyr-MIF-1 were hypersensitive on days 3, 8, and 9. Locomotor, passive avoidance, and rotorod behaviors were not altered by the neonatal treatments. Transport of [125I]Tyr-MIF-1 out of the brain was tested on day 23 and found to be increased by neonatal morphine, an effect that was significantly potentiated by neonatal Tyr-MIF-1. The results indicate that neonatal administration of peptides and opiates can affect later peptide transport across the blood-brain barrier as well as selected developmental characteristics.
Harrison
L M
LM
VA Medical Center, Research Service (151), New Orleans, LA 70146.
Zadina
J E
JE
Banks
W A
WA
Kastin
A J
AJ
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001522:Behavior, Animal / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D004723:Endorphins / Q000494:pharmacology*; D005123:Eye / Q000187:drug effects / Q000254:growth & development; D005260:Female; D006128:Growth / Q000187:drug effects*; D007457:Iodine Radioisotopes; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects*; D010147:Pain Measurement / Q000187:drug effects; D011247:Pregnancy; D051381:Rats
D000700:Analgesics; D004723:Endorphins; D007457:Iodine Radioisotopes; D009020:Morphine; C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone; C028889:morphiceptin