Open AccessEffect of morphine on the stimuli-induced calcium uptake into synaptosomes isolated from morphine-tolerant rats.
Author(s) -
Fukio Konno,
Issei Takayanagi
Publication year - 1982
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.32.625
Subject(s) - morphine , calcium , chemistry , depolarization , physical dependence , pharmacology , (+) naloxone , synaptosome , endocrinology , opioid , biochemistry , medicine , receptor , organic chemistry
Effects of morphine on calcium uptake into synaptosomes isolated from acutely or chronically morphine-tolerant rat brain was studied. Addition of morphine inhibited the depolarization-stimulated uptake of calcium without affecting uptake under nondepolarizing conditions. This inhibition was prevented by simultaneous addition of naloxone with morphine before calcium uptake was initiated. Acute tolerance to morphine increased depolarization-stimulated synaptosomal calcium uptake. On the other hand, chronic exposure of rats to morphine to elicit tolerance to and physical dependence on morphine did not influence synaptosomal calcium uptake. However, these preparations apparently lost the ability of in vitro morphine-inhibition of calcium uptake into the synaptosomes. Our results suggested that adaptive changes of synaptosomal calcium uptake produced by exposure to morphine may be involved in tolerance and physical dependence development, but influence of morphine on calcium uptake by the synaptosomes isolated from the rats acutely tolerance to morphine was differed from that of chronic tolerant rats.