Recovery of noradrenaline in adrenergic axons of rat sciatic nerves after reserpine treatment

The recovery of noradrenaline in adrenergic axons of the rat sciatic nerve after a single dose of reserpine (10 mg/kg i.p.) has been studied in unligated nerves and nerves ligated for 6 h. In unligated nerves the recovery at 24 h after reserpine was about 14% of normal. The noradrenaline content then slowly rose to reach about normal concentrations 6–7 days after reserpine injection. In nerves ligated 6 h before death, about 8·0 ng of noradrenaline accumulated proximal to the ligation in normal animals. At 6 and 12 h after reserpine about 4% of normal amounts of noradrenaline were found. Thereafter the amount of accumulated noradrenaline rapidly increased to about normal levels on day 2 after reserpine. At this time the content in unligated nerves was only about 45% of normal unligated nerve. On days 3–5 after reserpine, supranormal accumulations of noradrenaline were found (statistically highly significant), having a maximum at day 4 of about 145% of normal. At this time the noradrenaline content in unligated nerve was only about 80% of normal. The results may indicate an increased synthesis and increased rate of downtransport of amine storage granules during the early recovery phase after reserpine. This phenomenon may be part of a feed-back mechanism operating after depletion of the transmitter in the nerve terminals.