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Morphine activates calcium channels in cloned mouse neuroblastoma cell lines
Abstract:
Membrane effects of morphine on cloned neuroblastoma cells (strains NG108-CC15 and N1E-115), were studied using intracellular recording and ion flux techniques. Morphine (10 microM) induced a depolarization that was affected by changes in the concentration of calcium, but not in sodium. Further, morphine induced an uptake of 45Ca2+ which was blocked by naloxone (1 microM). The simplest explanation for the findings is that morphine activates calcium channels via mu-receptors.
Insights
Morphine affects neuroblastoma cells by altering calcium levels, suggesting it activates calcium channels through mu-receptors. This action influences cell membrane potential and calcium ion uptake.
Area of Science:
- Neuroscience
- Pharmacology
- Cell Biology
Background:
- Neuroblastoma cell lines (NG108-CC15, N1E-115) are utilized as models to study drug effects on neuronal membranes.
- Opioid receptors, particularly mu-receptors, are known to modulate cellular functions in the nervous system.
Purpose of the Study:
- To investigate the membrane effects of morphine on cloned neuroblastoma cells.
- To elucidate the role of calcium and sodium ions in morphine's action.
- To determine the receptor subtype involved in morphine's effects.
Main Methods:
- Intracellular recording techniques were employed to measure membrane potential changes.
- Ion flux assays using 45Ca2+ were performed to quantify calcium uptake.
- Pharmacological manipulation with naloxone was used to identify receptor involvement.
Main Results:
- Morphine (10 microM) induced a significant depolarization in neuroblastoma cells.
- The observed depolarization was dependent on extracellular calcium concentration but not sodium concentration.
- Morphine treatment led to an increased uptake of 45Ca2+ into the cells.
- Naloxone (1 microM) effectively blocked the morphine-induced calcium uptake.
Conclusions:
- Morphine's effects on neuroblastoma cell membranes involve alterations in calcium ion permeability.
- The findings strongly suggest that morphine activates calcium channels.
- Activation of calcium channels by morphine occurs through the engagement of mu-opioid receptors.