A new study by reseachers from the Children's Hospital Boston, have found a new anaesthetic approach which stops pain without affecting motor function.
The study group, led by Daniel Kohane of the Division of Critical Care Medicine at Children's, originally planned to find an agent that would prolong the anaesthetics' effects. They focused on surfactants, a subclass of "chemical permeability enhancers" that allow drugs to spread more easily throughout a tissue.
As the researchers tested three kinds of surfactant along with the anaesthetics QX-314 and QX-222 - both derivatives of lidocaine - they found that this approach prolonged the sensory block in rats' sciatic nerves, for nearly 7 hours or more depending on the surfactant, but didn't prolong motor impairment; in some cases the motor block was absent or of very short duration.
This meant that rats were able to tolerate having their paws on a hot plate for long periods, while still being able to balance and bear weight on their legs.
Kohane said: "This was a surprise finding...What we've discovered really is a new approach; the question now is to figure out the mechanism by which it works and look at the effects of other chemical permeability enhancers."
Kohane believes that surfactant helped the anaesthetic to penetrate sensory nerves, which have little or none of the fatty coating known as myelin, whereas in motor neurons, which have abundant myelin, the active drug gets trapped in the myelin, never entering the nerve itself.
The finding could help provide a local anaesthetic for childbirth in humans that would block pain without interfering with the mother's ability to push or for musculoskeletal disorders where it is important to maintain mobility.he study has appeared in the online Early Edition of the Proceedings of the National Academy of Sciences. (ANI)