Ontogenetic studies of tolerance development: effects of chronic morphine on the hypothalamic-pituitary-adrenal axis.

Journal Article (Journal Article)

Endogenous opiates are important regulators of the hypothalamic-pituitary-adrenal (HPA) axis in rats. Tolerance clearly develops to morphine-induced stimulation of the HPA axis in adult rats (Ignar and Kuhn 1990). The goal of the present study was to determine whether tolerance to morphine-induced stimulation of the HPA axis developed in neonatal and weanling rats treated chronically with morphine. Rats were injected with morphine or saline between days 4-8 postnatal (pups) or days 21-25 (weanlings) and tolerance assessed by determining dose-response curves for ACTH and corticosterone secretion following an acute morphine challenge. Weanlings displayed marked tolerance to the stimulation of ACTH and corticosterone secretion by morphine. Tolerance was also observed in pups to morphine-stimulated ACTH and corticosterone release. These findings suggest that the relative adaptability of the HPA axis to chronic morphine in neonatal and weanling rats is similar.

Full Text

Duke Authors

Cited Authors

  • Little, PJ; Kuhn, CM

Published Date

  • November 1995

Published In

Volume / Issue

  • 122 / 1

Start / End Page

  • 78 - 84

PubMed ID

  • 8711068

International Standard Serial Number (ISSN)

  • 0033-3158

Digital Object Identifier (DOI)

  • 10.1007/BF02246445


  • eng

Conference Location

  • Germany