Narcotic tolerance and dependence: lack of relationship with serotonin turnover in the brain

Serotonin turnover was measured in mouse brain by means of the conversion of radioactivity from labeled tryptophan into serotonin. Animals with a high degree of tolerance to and physical dependence on morphine did not differ from control mice.

Tolerance to opioid narcotics, II. Cellular tolerance to levorphanol in mouse brain

Mice were made tolerant to a large dose of levorphanol, a congener of morphine. Then (3)H-levorphanol was given. The concentration of free, unchanged levorphanol in the brain water (ultrafiltrate) was found to be much higher than required to produce pharmacologic effects in nontolerant animals. The result indicates that tolerance arises from a diminished sensitivity to the drug at cellular or subcellular sites of drug action in the brain.

Antagonism by physostigmine of the "running fit" caused by levorphanol, a morphine congener, in mice

1. Drugs of the morphine type cause a stereotyped "running fit" in the mouse.2. The intensity and duration of this response are related to the dose.3. Measurement of this phenomenon serves as a good method for the quantitative comparison of drugs of this type and for the study of their antagonists.4. Intracerebral injection of physostigmine antagonized the "running fit" induced by a wide range of doses of levorphanol.5. The results are consistent with the hypothesis that drugs of the morphine type act by retarding the release of acetylcholine at some central cholinergic synapses.