The effect of adrenalectomy on the development of morphine tolerance and physical dependence in mice.

1. A molecular sieve morphine pellet implanted for 24 h induced measurable tolerance and physical dependence in mice. 2. Adrenalectomy sensitized the animals to the antinociceptive effective of morphine. However, the degree of tolerance induced by morphine pellet implantation was not significantly affected. 3. Quantitative assessment of naloxone-precipitated withdrawal symptoms showed that adrenalectomy slightly enhanced the development of physical dependence. 4. These results indicate that adrenalectomy has no effect on the rate of development of morphine tolerance but may be involved in the development of physical dependence.