Effects of morphine tolerance and dependence on Mg++ dependent ATPase activity of synaptic vesicles

Hiroaki Yamamoto, R. A. Harris, H. H. Loh, E. L. Way

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14 Scopus citations


The effect of morphine on ATPase of synaptic plasma membranes (SPM) and synaptic vesicles isolated from the mouse brain was studied. The activity of synaptic vesicle Mg++-dependent ATPase from mice rendered morphine tolerant and dependent by pellet implantation was 40% higher than that from placebo implanted mice. However, the activities of Mg++-dependent ATPase and Na+, K+ activated ATPase of SPM of tolerant and nontolerant mice were not significantly different. The activity of synaptic vesicular Mg++-dependet ATPase was dependent on the concentration of Mg++ but not of Ca++; maximum activity was obtained with 2 mM MgCl2. On the other hand, Mg++-dependent ATPase activity of SPM was dependent on both Mg++ and Ca++, activity being maximum using 2 mM MgCl2 and 10-5 M CaCl2. It is suggested that this stimulation of ATPase activity may alter synaptic transmission and may thus be involved in some aspects of morphine tolerance and dependence.

Original languageEnglish (US)
Pages (from-to)1533-1539
Number of pages7
JournalLife Sciences
Issue number9
StatePublished - May 1 1977

Bibliographical note

Funding Information:
This study was supported by research grants from the National Abuse .

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