dye

In fact, there is a way to 'jam' the signal.  It is used by some dentist when removing a teeth without pain-killer.

The idea is that ''non-pain' signal has priority over 'pain' signal.  The fact that pain and non-pain signal uses the same nerve to transmit the message to therain.

The result is to use a shaking machine that shake at a particular frequency in the mouth, filling all the signal in the mouth with this 'shaking' message.  The 'pain' signal will hence not be felt.  
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Other method of nullifying the pain include:

a) physically cut the link
b) inhibit the receptors in the brain (like using coffee to the receptor of tired)
etc