The researchers at the Harvard Medical School and Massachusetts General Hospital said the compound, when injected into rats, completely blocked pain without interfering with either motor function or sensitivity to non-painful stimuli.

The researchers, led by Professors Clifford Woolf and Bruce Bean, said the technique could revolutionize pain management, since it specifically targets pain-sensing neurons. Current local anesthetics block all neurons, not just pain-sensing ones, and produce dramatic side effects such as temporary paralysis and complete numbness.

"We’ve introduced a local anesthetic selectively into specific populations of neurons," said Bean.

Woolf said he's optimistic the method will eventually be applied to humans, affecting procedures ranging from knee surgery to tooth extractions.

The work builds on research conducted since the 1970s showing how nervous system electrical signaling depends on ion channels, that is, proteins that make pores in the membranes of neurons.

"This project is a perfect illustration of how research trying to understand very basic biological principles can have practical applications," said Bean.

The discovery is reported in the Oct. 4 issue of the journal Nature.