The Body Electric - Micro-ondes

60 The Body Electric
possibility was the neurotransmitter acetylcholine, one of several com-
pounds known to relay nerve impulses across synapses. The nerves se-
creted acetylcholine more abundantly than normal during blastema
formation—just when nerve supply was crucial—and its production fell
back to normal when regrowth was well under way. Singer had studied
previous failures with acetylcholine, in which experimenters had rubbed
it on the stump or injected it into the blastema. He thought these meth-
ods were too artificial, so he invented a microinfusion apparatus to re-
lease tiny amounts of acetylcholine continually, just as the nerves did. It
used a clock motor to drip the hormone slowly through a needle into the
shoulder of an anesthetized animal in which the leg nerves had been
removed. He had trouble keeping the drugged salamanders alive, so
maybe the anesthetic affected the outcome, but even the ones that sur-
vived didn't regenerate at all. The growth factor was almost certainly
not acetylcholine.
Vital Electricity
These, then, were the shoulders on which I stood in 1958 as I began to
look for the pattern-control and blastema-stimulating factors in re-
generation. At that time we knew of two things that could yield some
regrowth in nonregenerators: extra nerve and extra injury. How were
they related? Luck gave me a clue.