Abstract
Cultured astrocytes from the cerebral cortex of the rat respond to opioid κ-receptor stimulation with a substantial elevation of the cytoplasmic free calcium, visualized through the use of the fluorescent calcium indicator Fura-2. The stimulation of κ-receptors with U-50488H increases the level of calcium through a dose-related stimulatory effect on the transmembrane calcium influx. The κ-receptor stimulation was completely blocked by the selective κ-receptor blocker nor-binaltorphimine. Furthermore, the transmembrane calcium influx was completely blocked by nifedipine, indicating the involvement of l-type channels. The presence of l-type channels was verified by stimulation of l-type channels with Bay K8644. The effects of Bay K8644 were completely blocked by nifedipine. l-type channel-coupled κ-receptors on astrocytes might represent a novel mechanism contributing to the depressant action of opioids on synaptic transmission via decreasing the availability of extracellular calcium necessary for presynaptic transmitter release.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
