Further evidence for the involvement of microtubules in the proximo-distal intra-axonal transport of acetylcholine and related enzymes in rat sciatic nerve

The effect of antimitotic agents on the intraneuronal distribution of lysosomes

We previously showed that a single injection of colchicine into the lateral cerebral ventricle of the rat causes a redistribution of lysosomes from their normal localization in neuronal cell bodies into dendrites. In the present report we have examined the time course and specificity of this effect using a variety of microtubule poisons. Dipeptidylaminopeptidase II (Dpp II), a lysosomal marker enzyme, histochemistry was used to visualize lysosomes at the light microscopic level. Acid phosphatase, another lysosomal enzyme, histochemistry was used to confirm the Dpp II localization of lysosomes. Two h after an intracerebroventricular (i.c.v.) injection of colchicine, the distribution of neuronal lysosomes was drastically altered. Lysosomes in a number of neuronal populations were observed to move from the soma to the dendrites. This effect was maximal between 12 and 24 h and was partially reversed by 96 h. Injections of colcemid or podophyllotoxin, drugs that bind to tubulin rapidly, and much less tightly than colchicine, produced a much less pronounced alteration in the intraneuronal distribution of lysosomes. Injections of vinblastine or vincristine, whose binding kinetics range between that of colchicine and that of colcemid and podophyllotoxin, resulted in a redistribution of lysosomes which was less pronounced than the effects of colchicine but more pronounced than that caused by colcemid and podophyllotoxin. Likewise, treatment with other related compounds, 2-methoxy-5-(2',3',4'-trimethoxyphenyl)tropone (A-C compound) and lumicolchicine, whose binding to tubulin is extremely rapid and reversible or non-existent, produced little or no alteration in the intraneuronal distribution of lysosomes. The results suggest that lysosome redistribution may be dependent upon a relatively slow dissociation rate constant of these drugs from tubulin, and this transport may occur when normal microtubule function is compromised.

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.

Systemic effects of colchicine on phosphate metabolism in innervated and denervated, slow and fast muscles of the rat

A single systemic injection of 75 micrograms colchicine/100 g body weight increases the permeability to inorganic phosphate of both fast gastrocnemius and extensor digitorum longus muscles and of the slow soleus muscle. In the two fast muscles, there is a significant interaction between colchicine treatment and 5-d- or 30-d- surgical denervation. In the slow soleus muscle there is no interaction between 5-d-colchicine treatment and the initial decrease in phosphate flow due to 5-d-surgical denervation but a significant interaction between colchicine treatment and the secondary increase in phosphate permeability observed after a 30-d-surgical denervation. Thirty days after a single systemic injection of colchicine the muscle phosphate metabolism is still perturbed especially in the slow soleus muscle in which the initial decrease in radioactive uptake associated with a 5-d-surgical denervation is inapparent. It is proposed that colchicine induces denervation-like alterations in the Pi- and POAS metabolism of skeletal muscles through mechanisms which are also activated -- partly or entirely -- by surgical denervation. These alterations do not result from the interruption of the axonal flow. A direct effect on the muscle membrane seems less likely than a disinhibition or activation of the muscle protein synthesis system.

The intra-axonal transport of acetylcholine and cholinergic enzymes in rat sciatic nerve during regeneration after various types of axonal trauma

The proximo-distal intra-axonal transport of acetylcholine (ACh) and cholinergic enzymes (choline acetyltransferase, CAT, and ACh-esterase, AChE) in rat regenerating sciatic nerve was studied by accumulation technique. Four types of axonal trauma were performed: freezing with solid CO2, crushing, ligating the nerve with remaining tight silk ligature, and cutting the nerve. Normal and sham-operated rats were used as controls. One to twenty-nine days later, the nerves were crushed about 15 mm proximal to the trauma. The nerve segment proximal to this crush was dissected out 12 hr later and assayed for ACh-content and enzyme activities. The increase in this segment 12 hr after crushing was taken as an indication of proximo-distal transport in the regenerating nerves. ACh transport did not seem to vary during regeneration as compared to controls. In contrast, the transport of both CAT and AChE was initially markedly depressed. Towards the end of the observation period (29 days), a recovery of CAT-transport occurred in all groups. Recovery of AChE-transport was marked in the freeze and crush groups. In the cut group no recovery was seen and in the ligated group only a small recovery occurred. Thus, in the nerves where regeneration was facilitated by the presence of intact connective tissue sheaths (freezing and crushing) recovery of transport occurred earlier than in cut or ligated nerves.