On the noradrenaline loading in axonal amine storage granules in rat crushed sciated nerves

Quantification of axonally transported material using cytofluorimetric scanning

This paper describes in detail a cytofluorimetric scanning technique used for studying amounts of material axonally transported in antero- and retrograde direction in peripheral nerves. Operating procedures, preparation of tissues and instrumental set-up are described. The basis for quantification of material in a nerve section treated for immunofluorescence is discussed. The reliability of the method has been tested by comparing results with biochemical data. There are several advantages of the technique. (1) Many different substances can be studied in one single nerve segment, thus reducing biological variation and costs. (2) Both morphological data and quantitative figures can be obtained; following scanning the section can be photographed. (3) The method can also be used on studies in the central nervous system and on tissue cultures, since it is possible to scan on single axons or bundles of fibres.

Cytofluorimetric scanning: a tool for studying axonal transport in monoaminergic neurons

A new technique is described which makes it possible to measure several substances and parameters related to axonal transport in peripheral nerves. The technique is based on histofluorescent techniques and measures accumulated amounts of fluorescent substances, e.g. proximal to a crush or local cooling of the nerve. Sections from nerves, treated according to the FIF method for visualization of catecholamines or for immunofluorescence, are placed in a cytofluorimeter (Leitz MPV 2). The nerve sections are passed under a measuring slit by a motor-driven cross-table and the fluorescence intensity is continuously registered via a recorder with integrator which gives a graphical "nerve-accumulation profile." Comparisons between accumulation curves obtained with the cytofluorimetric scanning technique and biochemically determined accumulation curves of noradrenaline, dopamine-beta-hydroxylase and tyrosine-hydroxylase in the sciatic nerve following crush operations, demonstrated a striking similarity. With this technique it is possible to semiquantify the accumulated amount of a fluorescent substance, study morphology, perform morphometry and photographical documentation in the same section. This scanning technique may prove useful, since the accumulation and distribution of several substances in consecutive sections, along the length of a nerve, can be demonstrated graphically using superimposed curves.

Noradrenaline and dopamine-beta-hydroxylase levels in rat salivary glands after preganglionic nerve stimulation: evidence for re-use of amine storage granules in transmitter release

The levels of endogenous noradrenaline (NA) in rat salivary glands were reduced to about 40 per cent after 1 hour of preganglionic stimulation at 4 Hz. Following 2 to 3 hours of rest the NA values had recovered to normal and remained normal for 6 hours after the stimulation. The recovered NA could be depleted by renewed nerve stimulation. After treatment with reserpine the NA disappeared almost completely. The recovered NA is discussed to be mainly present in amine storage granules that are re-used for storage and transmitter release. The axonal down-transport of new granules to the nerve terminals appears to be too small, as based on earlier results, for being of any quantitative importance in the experimental situation. The dopamine-beta-hydroxylase (DBH) level in the glands did not significantly change after the period of stimulation. The DBH content remained mainly unchanged following either post-stimulation recovery, repeated stimulation, or reserpine treatment. First when the glands were stimulated for 4 hours, there was a small decrease of the DBH levels. The mainly unchanged levels of DBH after stimulation does not appear to be explained by "trapping" in the tissue of released DBH, or recovery of the DBH by a marked axonal down-transport of new granules, as based on earlier results. The results of the DBH estimations support the view that the granules are not consumed to any marked extent at nerve activity, but can be re-used for nerve transmission. Furthermore, the results are in agreement with lack of correlation between released NA and released DBH.

Characteristics of the axonal transport of vasoactive intestinal polypeptide (VIP) in nerves of the cat

The axonal transport of vasoactive intestinal polypeptide (VIP) was examined in anesthetized cats. The distally directed (anterograde) flux of peptide was found to be about 35 fmol/h in the sciatic nerve. A smaller retrograde flux (8.5 fmol/h) weas also detected. In ulnar, radial and sciatic nerves, the average velocity of transport was calculated to be 2.5 mm/h in the anterograde and 0.6 mm/h in the retrograde direction. Clearance experiments indicated that the amounts of peptide available for transport in these two phases were 28% and 15% of the total, respectively. Estimates of true velocity based on these figures are 9 mm/h for anterograde transport and 4 mm/h for retrograde transport. Local injections of vinblastine were found to induce marked local increases in VIP-immunoreactivity, indicating that microtubules play a role in peptide transport. Subcellular distribution experiments showed that most of the transported VIP was associated with a particulate fraction, possibly corresponding to large vesicles. Only one molecular form of VIP-immuno-reactivity was detected by gel permeation chromatography and no evidence was obtained for cleavage of VIP precursors in the axon. Comparison of axonal flux of peptide with the apparent content of VIP in terminal regions indicated that the turnover time for this peptide is 5 days or longer in the periphery. The results are consistent with the view that peripheral neurons are dependent upon rapid axonal transport for the supply of vip to their terminals.

Axonal transport of dopamine-beta-hydroxylase to rat salivary glands: studies on enzymatic activity

The method by Nagatsu and Udenfriend (1972) to measure dopamine-beta-hydroxylase (DBH) activity was applied for tissue samples. Proximal to a crush or a ligature of the perihilar tissue of the rat salivary glands, DBH activity was found to increase about linearly with time. However, more DBH activity accumulated after ligation than after crushing. Noradrenaline (NA) accumulated also after a ligature but the increase appeared to exceed a linear one. The same pattern for the increase in NA we earlier had observed proximal to a crush of the rat sciatic nerve. It was now found that the accumulation of DBH activity was about linear with time in the crushed sciatic nerve, without any signs of supra-normal increase. The same increase was found after a crush as after a ligature. The ratio of accumulating NA and DBH activity agreed in the two neuronal systems.

Rapid transport of noradrenaline in adrenergic axons of rat sciatic nerve distal to a crush

The transport of NA in the rat sciatic nerve distal to a crush was studied in 5 mm segments. The disappearance of a NA fraction in consecutive segments with time after crushing (0-12 h) was interpreted to indicate a proximo-distal migration of a NA fraction into further distal parts of the nerve. This transportable NA fraction was found to be about 45% of the NA in normal sciatic nerves and migrated at a rate of approximately 8 mm/h. The apparently non-mobile fraction (55%) was probably mainly located in vaso-constrictor nerve terminals of the blood vessels supplying the nerve. This non-mobile NA fraction does not contribute to the NA accumulations proximal to a crush. Thus, when calculating the rate of transport of any substance from accumulation experiments, corrections for a non-mobile fraction must always be considered.