Sodium channels
Main function
Voltage-gated sodium channels open when the electrical charge across a cell membrane changes, allowing sodium to rapidly enter the cell. This creates the electrical signals used by nerves to transmit information, by skeletal muscles to contract and by the heart to maintain its electrical rhythm. Different sodium channel subtypes are specialized for the brain, peripheral pain nerves, skeletal muscle and heart.
Main body locations
Positive and negative describe interaction direction, not whether an effect is good or bad. Activating a target can have unwanted effects, while reducing or blocking it can sometimes have beneficial effects.
Increased activity
Increased sodium channel activity makes nerve and muscle cells easier to activate and can increase the transmission of pain signals. Excessive activity in certain sodium channels can also contribute to repetitive nerve firing and seizure activity. Some sodium channel subtypes are especially important in pain-sensing nerves, which makes them an important target in research into chronic and neuropathic pain.
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Reduced or blocked activity
Reduced sodium channel activity makes nerves less likely to fire repeatedly, which can decrease pain signalling and excessive nerve activity. This mechanism may contribute to some of the pain-relieving and anticonvulsant effects studied for cannabinoids such as CBD. A stronger real-world example is lidocaine: local anaesthetics block sodium channels sufficiently to temporarily stop pain signals from travelling through nearby nerves. Sodium channel blockers are also used medically for conditions such as epilepsy and certain abnormal heart rhythms.