On the Noradrenaline Loading in Axonal Amine Storage Granules in Rat Crushed Sciated Nerves1

Abstract

The increase of NA in rat sciatic nerve above a crush was investigated. The transported amounts of NA did not increase quite linearly with time, but more NA was found above the crush at 6 and 12 h than would be expected from the 3 h value. One possible reason for this phenomenon--an increased NA loading of the accumulated axonal granules--was investigated by 2 types of double crush experiments. One type involved simultaneous double crushes 1-1.5 cm apart. The increase in NA in the isolated segment 6 h after crushing indicated that the axonal amine storage granules had increased their NA load by about 70%. In the second type ("delayed double crushes") a distal crush was made 6 h before a second crush, 1-1.5 cm proximal to the first crush. 1-12 h after the second high crush the NA content of the isolated segment was assayed. The results indicated an increased NA content in the axonal granules of 75% already 3-4 h after the isolation of the segment, remaining constant up to 9 h after the second crush. The results indicate that axonal storage granules may increase their NA content by a factor of about 2 (1.7) while being transported distally in the axons. This information together with the information from the preceding article of a mobile NA fraction of 45%, was used to calculate the rate of transport of NA granules proximal to a crush. The value obtained was 9 mm/h which is in good agreement with the value obtained for transport distal to a crush (8 mm/h) in the preceding article.