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KMID : 0360419840200010023
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Korean Journal of Pharmacology
1984 Volume.20 No. 1 p.23 ~ p.32
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Effects of Morphine on the Transmembrane Potential and the Short Circuit Current of Frog Skin
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Abstract
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The effects of morphine on the transmembrane potential and the short circuit current in the isolated frog skin were studied under different experimental conditions. The measurem ents of the transmembrane potential and the short circuit current were carried out according to Ussing and Zerahn´s method. Experimental results were summeriaed as follows:
1) 5x 10-3 M of morphine markedly depressed the transmembrane potential and the short circuit current of the naive preparation. The peak of these inhibitory effects of morphine was observed about 1 hour after administration of the drug.
2) However 10-4 M of naloxone did not affect these effects of morphine.
3) Decrease of K+, increase of K+ or Caz+ in the perfusate, markedly potentiated the inhibitory action of morphine on both transmembrane potential and short circuit current of the frog skin, and addition of Mnz+ to the solution depressed the effect of morphine on the transmembrane potential, while the inhibitory effect of morphine on the short circuit current was diminished in the Ca 2- -free ringer solution, and increase of Mgz+ concentration depressed those effect of morphine on both electrical parameters.
4) In the morphine treated preparations, transmembrane potential and short circuit current were decreased in the early phase of drug treatment (1-r2 days), but gradually increased to the significantly high level from the control (48 days after treatment). In these preparations, the effects of morphine on both electrical parameters were also potentiated in the early phase, but markedly diminished in the late phase of treatment.
From the above results, it is postulated that the pharmacological actions of morphine as well as development of the tolerance by morphine may be partially related to the changes of ion fluxes and/or permeabilities of skin by the drug.
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