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

Storage and fast transport of noradrenaline, dopamine beta-hydroxylase and neuropeptide Y in dog sciatic nerve axons

The axonal transport and subcellular distribution of noradrenaline (NA), dopamine beta-hydroxylase (DBH) and neuropeptide Y (NPY) were determined in dog sciatic nerve using an accumulation technique. The results were compared with those obtained by application of the same procedures and methods on the splenic nerve in the same animal species. Evidence was found for the coexistence of NA and NPY in large dense-cored vesicles in dog sciatic nerve axons. After differential centrifugation and isopyenic sucrose density gradient centrifugation of 24 h ligated sciatic nerve pieces NA and NPY equilibrated around 1M sucrose. The DBH activity was dispersed broadly on the gradient. Subsequently, the accumulation of NA, DBH and NPY was studied in proximal and sital segments of 8, 12 and 24 h dog ligated sciatic nerve and inferences were made concerning the axonal transport of these compounds. NA, DBH and NPY displayed a divergent accumulation proximal to the ligation. After 12 h of ligation a transport rate was calculated of 4.8 +/- 1.8 mm/h for NA, of 5.9 +/- 1.5 mm/h for DBH and of 4.9 +/- 2.0 mm/h for NPY. With a correction for the stationary fractions, a similar fast transport rate of approximately 10 to 12 mm/h was proposed for NA, DBH and NPY. The occurrence was shown of a limited retrograde transport of DBH and possibly NPY, but not of NA.

Subcellular storage and axonal transport of neuropeptide Y (NPY) in relation to catecholamines in the cat

The subcellular storage of neuropeptide Y-like immunoreactivity (NPY-LI) in peripheral sympathetic neurons and adrenal gland as well as its axonal transport in the sciatic nerve was studied in relation to catecholamines in the cat. In the subcellular fractions from different parts of sympathetic neurons, i.e. cell bodies (coeliac ganglia), axons (sciatic nerve) and terminals (spleen), the NPY-LI was found together with noradrenaline (NA) in heavy fractions assumed to contain large dense-cored vesicles. In addition, minor lighter fractions in the coeliac ganglion contained NPY-LI. The molar ratio between vesicular NA and NPY was high in the terminal regions (150 to 1) and much lower in axons and cell bodies (10 to 1), thus reflecting the different mechanisms of resupply for classical transmitter and peptide. In the adrenal gland the NPY-LI was mainly located in the catecholamine-storing chromaffin-granule fraction and also to a smaller extent in lighter fractions. Using reversed-phase HPLC, one molecular form of NPY-LI corresponding to porcine NPY was found in the coeliac ganglion, while the adrenal medulla also contained minor peaks with NPY-LI in addition to the main form, which co-eluted with porcine NPY. NA was stored both in light and heavy fractions in the spleen, while it was mainly found in heavier fractions in the sciatic nerve. In the coeliac ganglion, most of the noradrenaline was present in a non-particulate form. The anterograde transport rate for NPY-LI in the sciatic nerve was estimated to be about 9 mm h-1. A minor retrograde transport of NPY-LI was also detected. In conclusion, the present data suggest that NPY, a peptide with sympathoactive actions, is co-stored with NA in heavy fractions corresponding to large dense-cored vesicles, while light fractions with small dense-cored vesicles probably contain NA but not NPY-LI. The main resupply of NPY to terminals is, in contrast to NA, most likely by axonal transport, which implicates differences in the storage, turnover and release of these co-existing substances in the sympathoadrenal system.

Cholecystokinin in feline vagal and sciatic nerves: concentration, molecular form and transport velocity

The axonal transport velocity of immunoreactive cholecystokinin (CCK) was examined in the vagal and sciatic nerves of anesthetized cats after determination of the molecular form of CCK by sequence-specific radioimmunoassay and gel chromatography. Extracts of the peripheral nerve branches, corresponding spinal ganglia, brainstem and spinal cord, contained mainly CCK-8-like immunoreactivity. In addition a large molecular form eluted immediately after the void volume of Sephadex G-50 columns, and occasionally minor C-terminal fragments were discovered. A single vagal nerve and one medulla oblongata also contained gastrin-17-like material. Significant differences in the relative amounts of the molecular forms of CCK in the different regions and nerves were not apparent. The distally directed (anterograde) flux of CCK was found to be 78 fmol/h in the sciatic nerve and 50 fmol/h in the vagus. Significant retrograde transport was not detectable. Based on these figures the true velocity for the anterograde transport was estimated to be 7 mm/h for CCK in the vagus and 8 mm/h in the sciatic nerves. The results indicate that CCK-8-like peptides are rapidly transported distally without significant axonal processing of CCK precursors.

Disappearance of noradrenaline from different parts of the rabbit external ear following superior cervical ganglionectomy

Following superior cervical ganglionectomy the noradrenaline tissue levels in the base of the rabbit external ear started to decrease after about 12 hours. About 4 hours later noradrenaline started to decrease about simultaneously in the middle piece and the tip. Within 24 hours after ganglionectomy the noradrenaline decreased rapidly in all three pieces. Thereafter the noradrenaline of the base piece was levelling off at about 15% of the normal whereas the noradrenaline in the two other pieces remained at about 40% of the normal. The results indicate that the adrenergic innervation of the ear is complex, but that the base piece is supplied with adrenergic axons that are shorter than those of the middle and tip pieces. Based on 1: the delay of 4 hours observed in the pattern of the noradrenaline disappearance between the base and the two other pieces, and II: the difference in distance between the three pieces of the ear and the superior cervical ganglion, a transport rate of a "protecting factor" could be discussed to be about 1-2 cm/h. The rate of axonal transport of dopamine-beta-hydroxylase in the rabbit sciatic nerve, was found to be within the same range, being about 2 cm/h.

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 and subcellular distribution of dopamine-beta-hydroxylase in the cod, Gadus morhua

The axonal transport of dopamine-beta-hydroxylase (DBH; E.C. 1.14.17.1) was studied in the splanchnic nerve of the cod in vivo, and the subcellular localization of the same enzyme was studied in the chromaffin tissue from the cod head kidney. The mean rate of axonal transport for cod DBH was 18.6 mm/24 h at 10 degrees C. The mobile fraction was estimated to 22%, giving an absolute rate of transport of 85 mm/24 h at 10 degrees C. Evidence for a retrograde transport of DBH was also obtained, with an accumulation distal to a ligature of 12% of the accumulation proximal to the ligature at 3 days. DBH from the chromaffin tissue appeared to be strongly bound to the adrenergic granules, with only a small amount (ca 4%) recovered in the soluble phase.

Axonal transport of adrenaline, noradrenaline and phenylethanolamine-N-methyl transferase (PNMT) in sympathetic neurons of the cod, Gadus morhua

The axonal transport of adrenaline, noradrenaline and phenylethanolamine-N-methyl transferase (PNMT) has been studied in vivo in sympathetic neurons of the splanchnic nerve in the cod, Gadus morhua. Adrenaline and noradrenaline are transported at a mean axonal transport rate of 16 mm/day. After correction for a non-mobile fraction of adrenaline and noradrenaline, which does not contribute to the amine accumulation proximal to a ligature, a maximal rate of transport was calculated to about 45 mm/day for both amines. The increased level of catecholamines in front of a ligature could be depleted by reserpine treatment, which strongly suggests that both amines are stored in granules. PNMT is transported at a slow rate of 2 mm/day. The subcellular distribution of the cod PNMT was exclusively non-particular. The cod PNMT was further characterized by studying substrate specificity, temperature and pH optima. It is concluded that adrenaline and noradrenaline, stored in granules, are transported in a proximo-distal direction at a high rate compared to PNMT.

A histofluorescence study of events accompanying accumulation and migration of norepinephrine within locally cooled nerves

Glyoxylic acid was used to induce fluorescence in sections of rabbit sciatic nerve. In fresh nerves treated with this agent there were scattered finely beaded axons with a weak blue-green fluorescence. During local cooling, blue-green fluorescence accumulated steadily at the proximal boundary of the cooled region but never at its distal boundary. This accumulation gave rise to dilated axons that often swelled into brilliantly fluorescent balloon-like structures up to 10 microgram in diameter. Axonal fluorescence was probably specific for norepinephrine, being enhanced by inhibition of the metabolism and diminished by inhibition of the synthesis or storage of this neurotransmitter. After local cooling of nerves for 1.5 hr, specific fluorescence was confined within 0.8 mm of the cooled region. Rewarming led to rapid removal of fluorescence from the cooled region and to disappearance of most of the balloon-like swellings. Simultaneously, rewarming caused brightly fluorescent fibers that were neither dilated nor swollen to appear in distal regions of nerve. As this wave of fluorescence migrated distally with increasing duration of rewarming, it was spread over increasingly broad regions of nerve, which suggests that axonal transport of norepinephrine may invole some kind of dispersive process.

Degeneration secretion and noradrenaline disappearance in rat salivary glands following proximal or distal axotomy

The noradrenaline (NA) content and the degeneration secretion of saliva were studied in rat salivary glands, following proximal or distal sympathetic denervation. Proximal denervation was obtained by removal of the cervical superior ganglion, which left a long stump of adrenergic axons attached to the gland. Distal denervation was achieved by crushing the perihilar tissue, including the adrenergic axons, close to the gland, leaving only short axon stumps connected with the gland. Onset of both NA decrease and degeneration secretion occurred first in the distally denervated glands and about 2 h later on the proximally denervated sides. Except for the delay of 2 h the pattern of NA decrease and saliva secretion was similar after the two denervation procedures. The length of the attached axon stumps was estimated to be about 15-20 mm longer on the proximally denervated side. Therefore, the delay of 2 h caused by this length of axons corresponds to the proximo-distal intra-axonal transport distal to the "axotomy" of some protecting factors at the rate of 8-10 mm/h. Onset of degeneration secretion was observed between 11 and 12 h after proximal denervation when the NA content was decreased by about 10%. The maximum of saliva secretion occurred about 14 1/2 h after denervation when only 45% of the NA remained in the gland. The correlation between the degeneration secretion of saliva and the decrease in NA probably was due to 1) the amount of NA leaking from degenerating nerve terminals, and 2) the inactivation of this escaped NA by the re-uptake mechanism in the membrane of still intact nerve terminals.

Retrograde axoplasmic transport to inactive dopamine beta-hydroxylase in sciatic nerves

The transport of dopamine-beta-hydroxylase (DBH) in sciatic nerves was studied both by measuring the accumulated enzyme activity and by examining the accumulated immunologically reactive DBH protein. The pattern of DBH accumulation in the proximal segment was similar either in the activity or in the immunofluorescence. In the distal segment, however, much higher accumulation of immunofluorescence than that of the activity was observed 7 h after ligation. The immunotitration studies indicated that more DBH molecules were accumulated in the distal segment than in the proximal segment 5 h after ligation. The homospecific activity of DBH in the distal segment was about one-fifth of that in the proximal segment. The result suggests that relatively large amounts of inactive enzyme may be transported back to the soma instead of complete degradation in the terminal.

The effect of local application of vinblastine or cholchinine on acetylcholine accumulation in rat sciatic nerve

The accumulation of acetylcholine (ACh) following nerve crush was inhibited by high concentration of colchicine (10(-1), 10(-2 M) and vinblastine (10(-2)-10(-4 M) in a dose-dependent manner. The two mitotic inhibitors were effective both when applied to axons (subepineural injections) and to perikaraya (injections into the lumbar intumescence). The results indicate that mitotic inhibitors, when applied locally to cholinergic motor neurons, may block the proximo-distal transport of ACh. The possibility is discussed that this blockade is caused by an interference with a microtubule mechanism in the axons. Evidence for an increased local synthesis of ACh near the site of injection into nerves also obtained with the highest concentrations of either substance used.

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

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.