RECOVERY OF BLOOD-PERFUSED MAMMALIAN NERVES

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Abstract
Recovery of rabbit and cat sciatic nerve in vivo (animal etherized or decorticated) was recorded from the tibialis or gastrocnemius muscle or deep peroneal nerve by cathode ray oscillograph records of the response to a testing induction shock (usually submax.) at various intervals after one or more conditioning responses; recovery of the rabbit oculomotor nerve was similarly recorded from the internal rectus muscle or the nerve to the inferior oblique muscle. Recovery of excitability in its latter part varies considerably in different preps. and during the course of an expt. on one prep., presumably because the metabolic condition of the prep. cannot be maintained constant. The chief variation consists in the extent and amt. of the supernormal phase usually present between the refractory and subnormal phases. Supernormality occurs ordinarily under exptal. conditions after one conditioning response, but is absent in very fresh preps. and after rhythmic activity. Recovery of conduction velocity occurs more promptly than that of excit.; there are no late changes in vel. corresponding to the supernormal and subnormal periods of excit. The recovery of height conforms to that of vel. Rhythmic activity within physiol. limits does not affect the recovery of height and vel., nor that of excit. early in the rel. refrac. period, but greatly delays the later part of the recovery of excit. These exptl. findings suggest the division of the recovery cycle into 2 parts, during the 1st of which (1.5-2 msec.) height and vel. recover completely, and excit. recovers to an extent (roughly 80%) that does not change significantly after rhythmic activity. The completion of the recovery of excit. during the 2nd part of the cycle is greatly affected by rhythmic activity and other conditions. The conduction rate of the fastest fibers in the sciatic-peroneal preps. is constant from moment to moment and over long periods of time. It is not affected by separating the fibers from their central connections.

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