A story in Thursday's Washington Post described how military research scientists are producing spinal cord injuries in cats by "crushing" the spinal cords in order to learn how to prevent human injuries. Dr. John Holaday says the research involves dropping a light weight to bruise, but not crush, an anesthetized animal's cord to simulate a human injury while causing as little damage as possible.
Military scientists here have developed the most promising drug treatment yet for preventing total paralysis or near paralysis resulting from crippling spinal cord damage.
Their work with experimental animals, injecting a hormone called TRH (for thyrotropin-releasing hormone), dramatically increases the hope of preventing paralysis accompanying thousands of the spine injuries caused by auto, motorcycle and diving accidents.
The achievement is described as "dramatic" in an editorial in today's New England Journal of Medicine, where scientists at the Uniformed Services Health Sciences University and the Walter Reed Army Institute of Research report their results.
The scientists, Dr. Alan Faden, Thomas Jacobs and Dr. John Holaday, dropped heavy weights on cats to crush their spinal cords and duplicate the devastating spinal damage that occurs in an increasing number of human falls and other accidents every year.
The researchers waited an hour to approximate the time it takes most such victims to get to a hospital. Then they began four hours of continuous injection of TRH, a powerful substance produced by the hypothalamus, near the base of the brain.
They did this with six cats that otherwise would have died or at best would have walked with severe incoordination and spasticity. Four of the six walked normally and two others walked nearly normally.
Animals left untreated after the same kind of injury either died or eventually walked with great difficulty.
Some victims of spinal cord injury have the nerves in their spinal cord completely destroyed or severed, and inevitably become quadriplegics or paraplegics, bound to wheelchairs. This kind of drug treatment could not help them.
But many who suffer spinal cord trauma, like that experienced by the cats, also become quadriplegics or paraplegics or lose much of the power and use of their arms and legs.
These persons, treated very quickly, may in time be helped by TRH, or by some future drug now that it is clear that such a drug may work.
Quick treatment is important, because scientists have learned that much paralysis is caused not so much by the initial injury to the spinal cord as by the first six hours of interrupted blood flow to the crucial nerve cells within the cord.
Early last year Faden and Holaday reported restoring blood flow rapidly in cats with spinal cord damage by injecting a drug called naloxone. Naloxone acts by blocking a group of brain chemicals known as the endorphins.
Endorphins lower blood pressure and relieve pain, and giving the cats naloxone restored blood pressure and blood flow but also, it turned out, may have encouraged crippling pain.
TRH, like naloxone, partly blocks endorphin action. But it does so without interfering with the endorphins' pain relief.
Faden and Holaday also have used naloxone and TRH to combat physiologic shock. This is the drastic, often fatal fall in blood pressure that follows many kinds of injuries, nerve damage, hemorrhaging or bacterial infections.
This work too is done in experimental animals. Other investigators have already begun reporting successful naloxone use in human shock.