A method for the demonstration of adrenergic nerve fibres in peripheral nerves

The origin and nature of beading: a reversible transformation of the shape of nerve fibers

Nerve fibers which appear beaded (varicose, spindle-shaped, etc.) are often considered the result of pathology, or a preparation artifact. However, beading can be promptly elicited in fresh normal nerve by a mild stretch and revealed by fast-freezing and freeze-substitution, or by aldehyde fixating at a temperature near 0 degree C (cold-fixation). The key change in beading are the constrictions, wherein the axon is much reduced in diameter. Axoplasmic fluid and soluble components are shifted from the constrictions into the expansions leaving behind compacted microtubules and neurofilaments. Labeled cytoskeletal proteins carried down by slow axonal transport are seen to move with the soluble components and not to have been incorporated into and remain with, the cytoskeletal organelles on beading the fibers. Lipids and other components of the myelin sheath are also shifted from the constrictions into the expansions, with preservation of its fine structure and thickness. Additionally, myelin intrusions into the axons are produced and a localized bulging into the axon termed "leafing". The beading constrictions do not arise from the myelin sheath: beading occurs in the axons of unmyelinated fibers. It does not depend on the axonal cytoskeleton: exposure of nerves in vitro to beta, beta'-iminodipropionitrile (IDPN) disaggregates the cytoskeletal organelles and even augments beading. The hypothesis advanced was that the beading constrictions are due to the membrane skeleton; the subaxolemmal network comprised of spectrin/fodrin, actin, ankyrin, integrins and other transmembrane proteins. The mechanism can be activated directly by neurotoxins, metabolic changes, and by an interruption of axoplasmic transport producing Wallerian degeneration.

Fast and slow axonal transport-different methodological approaches give complementary information: contributions of the stop-flow/crush approach

This 'minireview' describes experiments in short term crush operated rat nerves, to study endogenous substances in anterograde and retrograde fast axonal transport. Immunofluorescence was used to recognize transported antigens, and cytofluorimetric scanning was employed to quantitate different antigens which had accumulated proximal and distal to the crushes. Vesicle membrane components p38 (synaptophysin) and SV2 accumulated on both sides of a crush. This was expected from a number of studies from different laboratories. Surface associated molecules, however, like synapsins and rab3a, have been studied by other groups with biochemical methods, and suggested to be transported with slow transport. The crush method, however, revealed that a considerable fraction of these two substances are transported with the fast transport system, and, thus, associated with fast transported organelles in the living neuron. Evidently, more than one technique is required to give a more complete picture of intraneuronal transport related events.

Immunohistochemical study of cholecystokinin peptide in rat spinal motoneurons

With the aid of indirect immunofluorescence histochemistry and sequence specific antibodies a possible localization of cholecystokinin (CCK) peptide in spinal motoneurons has been analyzed. To increase peptide levels, the sciatic nerve was ligated, and the area around the ligation was studied 24 hours later. For comparison, antisera raised against calcitonin gene-related peptide (CGRP) and substance P were employed. With CCK specific antisera (directed to the N-terminal portion of CCK-8 or the midportion of CCK-33) accumulation of peptide-like immunoreactivity (LI) was observed in large, dilated axonal swellings proximal to, but at some distance from, the ligature. Such accumulations were also observed with C-terminally directed CCK antiserum, but in addition numerous axons of smaller diameter extending up to the ligation contained this type of immunoreactivity. The latter antiserum is thought to cross-react with CGRP. In fact, this staining pattern was indistinguishable from the one seen after incubation with CGRP antiserum. In contrast substance P-LI could not be seen in the larger dilated axons but only in large numbers of thinner fibers close to the ligation. Double staining experiments revealed that the large dilations contained both CGRP- and CCK-specific LI. Distal to the ligation CGRP- and substance P- but no specific CCK-LI could be observed. The present findings support the view that CCK mRNA in spinal motoneurons is translated into CCK peptide, at least after axotomy, and that the peptide is transported into the motoneuron axon. However, compared to CGRP the CCK levels are presumably low, and the functional role of CCK peptide in motoneurons remains to be established.

A fluorescence study of changes in noradrenergic sympathetic fibres in experimental peripheral nerve neuromas

Experimental neuromas were produced in rats by sciatic nerve section and avulsion of the distal stumps. At intervals varying from 3 days to 8 weeks after nerve section, the developing neuromas were resected and processed for noradrenaline (NA) fluorescence microscopy by the sucrose-phosphate-glyoxylic acid (SPG) method. From serial longitudinal sections through the neuromas and the nerve proximally, counts of noradrenergic sympathetic axons were made, together with qualitative observations of axon sprouting and NA content. By 3 days after nerve section there was a massive sprouting of sympathetic axons, with increased NA content, particularly towards the distal tip of the neuroma. Axon counts remained high 1 week following section then fell to below normal levels at 2 weeks, returning towards normal 8 weeks after nerve section. These results are discussed in relation to the known pathophysiological interaction between sympathetic efferent and sensory afferent fibres, which develops in neuromas following nerve section.

Extrinsic pathways of the adrenergic innervation of the guinea-pig trachealis muscle

Origins and extrinsic pathways of the adrenergic innervation of the guinea-pig trachealis muscle were studied using fluorescence histochemical techniques. Bilateral superior cervical ganglionectomy caused a marked reduction in the adrenergic innervation of the extra-thoracic region, which suggests that these ganglia are a major source of adrenergic innervation to this muscle. Combined anterior and posterior transection of the recurrent laryngeal nerves also caused a marked reduction in the density of adrenergic fibres in the extra-thoracic trachealis muscle. Crushing of these nerves revealed adrenergic fibres running both anteriorly and posteriorly. The majority of these adrenergic nerves were lost after superior cervical ganglionectomy and thus the fibres running in both directions originate in the superior cervical ganglion. Antero-posteriorly directed fibres entered the recurrent laryngeal nerve from the superior cervical ganglion via an anastomosis at the level of the cricoid cartilage, while those running postero-anteriorly entered the recurrent laryngeal nerve posteriorly from the vagus nerve and these adrenergic fibres were lost after cervical vagotomy.

Effects of extrinsic denervation on net water transport and motility of the feline gallbladder in vivo

The influence on the concentrating ability of the gallbladder after extrinsic denervation was studied in anesthetized cats, previously subjected to truncal vagotomy, and/or celiacectomy , and compared with sham-operated controls. Net water absorption was studied by perfusion techniques. Acute experiments were performed under basal conditions and alpha-adrenoceptor stimulation (iv infusion of norepinephrine (NE), 1 micrograms/kg X min). Gallbladder biopsies were studied by fluorescence microscopy to visualize and quantitate catecholamines. Three weeks after celiacectomy basal absorption had decreased significantly. In the short-term vagotomy group no changes were demonstrated. However, in the long-term vagotomy group there was a fourfold increase in absorptive capacity, which decreased to control levels after alpha-adrenoceptor blockade (phentolamine 1 mg/kg iv). Long-term vagotomy with subsequent celiacectomy caused no significant changes. Infusion of NE increased net water absorption by 70 +/- 16% in all experimental groups except in long-term vagotomized animals, where the high basal absorption was not further augmented. One hour after NE infusion controls returned to basal absorption rate, while denervated cats remained at stimulated levels. In long-term vagotomized gallbladders there were morphological signs of adrenergic proliferation (increased total number of nerve terminals, sprouting, and elevated levels of intraneuronal NE). In conclusion these results suggest that the adrenergic nervous system is important for full absorptive capacity of the gallbladder. The increased absorption after long-term vagotomy, abolished after alpha-adrenoceptor blockade, might well be explained by the parallel adrenergic proliferation. This hypothesis was further corroborated in animals with long-term vagotomy, where subsequent surgical adrenergic denervation restored basal absorption to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of stellatectomy on gastric acid secretion in the dog

The stellate ganglion is the major contributor of adrenergic fibers to the vagus nerve and stellatectomy causes a degeneration of vagal adrenergic fibers. The purpose of this experiment was to evaluate the effect of stellatectomy on gastric acid secretion (GAS) and gastrin levels in the dog. GAS in response to pentagastrin stimulation was measured in six gastric fistula dogs before and after stellatectomy. Likewise, blood was collected for basal and meat meal-stimulated serum gastrin levels before and after stellatectomy. After bilateral stellatectomy acid secretion increased in response to submaximal doses of pentagastrin stimulation whereas maximal secretion was unchanged. Resting and meal-stimulated gastrin levels did not change. A Horner's syndrome developed in each dog. It is concluded that bilateral stellatectomy increases GAS in response to submaximal stimulation while not altering gastrin release. These results suggest that the vagal adrenergic innervation of the stomach has an inhibitory role in the control of GAS in the dog.

Rapid and precise down regulation of fast axonal transport of transmitter in an identified neuron

Within 1 day after the removal of one branch of the bifurcated axon of an identified neuron in Aplysia, the cell body reduced its output of transmitter storage vesicles to adjust precisely for the decreased need. This adjustment terminated the initial consequence of the removal, the transport of an inappropriately large number of vesicles to the remaining synapses. The most likely cause of the reduction of transport of transmitter is the loss of information normally provided by the disconnected axon or synapses.

Evidence for a non-classical splanchnic neural control of the feline pylorus

Electrical stimulation of the divided splanchnic nerves proximal to the celiac ganglion in chloralosed cats induced a dilation of the pylorus in the majority of animals. However, in some cats a pure contractile motor response or a biphasic motor response (contraction followed by dilation) was elicited suggesting that the splanchnic nerves convey excitatory fibres to the pylorus as well. The pyloric and gastric contraction at such stimulation was sensitive to atropine, while the pyloric dilation was not sensitive to cholinergic, adrenergic or ganglionic blocking agents in contrast to the adrenergic gastric dilation. Since the splanchnic nerve and the pyloric wall contain numerous neuropeptides, these substances might be involved in a nonclassical neurotransmission of the splanchnic motor responses of the pylorus.

Neurohumoral observations and the gastrointestinal tract

Vagal interrelationships with the gastric antrum have been studied in depth. A special experimental model, antroneurolysis, demonstrated that the function of the gastric mucosa is maintained after removal of central neural control, that is, vagotomy. A series of experiments are reported which demonstrate the importance of the sympathetic nervous system in the local control of gastrointestinal function. The concept of local neural control of the endocrine and secretory function of the epithelial cells of the intestinal mucosa (internal brain) is proposed.

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.

Branching patterns and projections of enteric neurons containing different putative transmitters

Methods have been developed for the microsurgical interruption of nerve pathways in the wall of the intestine and for the immunohistochemical localization of antigens in whole mounts. These methods have made it possible to determine accurately the distributions and projections of neurons containing different putative transmitters. In this week neurons with substance P, somatostatin and 5-hydroxytryptamine-like immunoreactivity are described. Projections of noradrenergic neurons are also demonstrated. Each substance is associated with a unique set of neurons having precise projections within the intestine.

Leucine enkephalin: localization in and axoplasmic transport by sacral parasympathetic preganglionic neurons

Nerve processes and cell bodies containing leucine enkephalin were demonstrated in the sacral autonomic nucleus of the cat by immunocytochemical methods. Enkephalinergic preganglionic perikarya were seen only when axonal transport was blocked either by colchicine or by ventral root ligation. Ligation of the sacral ventral roots also produced damming of enkephalin immunoreactivity proximal to the S2 ligature. These data indicate that parasympathetic preganglionic neurons synthesize and transport enkephalin or enkephalin-like immunoreactive compounds to the periphery.

Origin of the adrenergic nerve fibers in the subdiaphragmatic vagus in the dog

The vagi at the subdiaphragmatic level were studied by the Hillarp-Falck technic in combination with a nerve crush procedure in three normal dogs and in eight dogs that had undergone previous surgical excision of the superior cervical ganglion and/or the stellate ganglia. Unilateral ganglionectomies were performed so that the contralateral vagus served as a control. Based on these results, it is concluded that: (1) the subdiaphragmatic canine vagus contains numerous adrenergic nerve fibers; (2) the main portion of these vagal adrenergic fibers arises from the stellate ganglia; and (3) removal of both the stellate and the superior cervical ganglia results in nearly complete adrenergic denervation of the abdominal vagus.

Effects of chronic deafferentation on adrenergic ganglion cells and small intensely fluorescent cells

To determine the reaction of adrenergic ganglion cells and small intensely fluorescent (SIF) cells to chronic deafferentation, catecholamine fluorescence of the major pelvic ganglion (MPG) of the rat has been studied following section of the hypogastric nerve, pelvic nerve and sympathetic trunk. Only minor changes occurred following section of the hypogastric nerve; the fluorescence surrounding a few adrenergic ganglion cells became brighter. In contrast, pelvic neurectomy resulted in the appearance of numerous varicose fibres and an increase in the fluorescent intensity of fibres enclosing many ganglion cells. Varicose fibres seem to originate from adrenergic ganglion cells and SIF cells. In many instances, nests of SIF cells gave rise to radially oriented fibres. Removal of the sympathetic trunk appeared to have no effect on the MPG. It is suggested that the appearance of varicose fibres from SIF cells following deafferentation may be due to collateral sprouting of these cells or to the increased fluorescence of pre-existing processes.

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.

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.