Naltrexone modulates body and brain development in rats: A role for endogenous opioid systems in growth

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110 Scopus citations

Abstract

Preweaning rats receiving daily injections of 20, 50, or 100 mg/kg naltrexone, a potent opiate antagonist, has body and brain weights that were increased 16-22% and 6-13%, respectively, from control levels on day 21 (weaning). All of these dosages of naltrexone blocked the opiate receptor for 24 hr/day as measured in opiate challenge experiments. Dosages of 0.1, 1, and 10 mg/kg naltrexone, which blocked the opiate receptor for less than 12 hr/day, inhibited growth. Repetitive administration of low dosages (3 mg/kg naltrexone, 3 times daily), which blocked the receptor 24 hr/day, increased body and brain development by 31% and 10%, respectively, whereas a cumulative dosage of 9 mg/kg naltrexone given once daily retarded growth. These results show that developmental events are dictated by the duration of opiate receptor blockade and provide compelling evidence that endogenous opioid systems play a crucial role in growth.

Original languageEnglish (US)
Pages (from-to)2057-2064
Number of pages8
JournalLife Sciences
Volume35
Issue number20
DOIs
StatePublished - Nov 12 1984

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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