Distribution of GAP-43 in relation to CGRP and synaptic vesicle markers in rat skeletal muscles during development

Age-related changes and the possible adaptability of rat jaw muscle spindles: immunohistochemical and fine structural studies

Afferent signals from jaw muscle spindles contribute to the feedback mechanism that regulates mastication. The integrity and adaptability of this proprioceptor to age-related changes of the surrounding structures are therefore essential to maintain an appropriate masticatory function throughout life. In this study, we examined muscle spindles obtained from temporal and masseter muscles of 10-week-, 12-, 18-, and 24-month-old Wistar rats, employing immunohistochemistry for protein gene product 9.5 (PGP 9.5) or growth-associated protein (GAP-43) in addition to transmission electron microscopy, in order to investigate their morphological changes in relation to the effect of aging on the adaptive potential of the receptors. Immunohistochemistry for PGP 9.5 showed virtually similar reactions at sensory nerve terminals in all age groups. On the other hand, immunoreactivity for GAP-43 in the sensory nerve ending of the muscle spindles was found 2 and 3 weeks after birth but became almost undetectable by 10 weeks. However GAP-43 immunoreactions occasionally reappeared in those of spindles in 12- and 18-month old animals, and vanished again by 24 months of age. Electron microscopic observations also revealed age-related morphological changes in the intrafusal muscle fibers of the rats in 12-month and older groups. The extent of degenerative and/or atrophic alterations of intrafusal fibers increased with age and involved the nerve elements of spindles by 24 months. These findings indicate that the adaptation potential of rat jaw muscle spindles is well preserved until middle age, but diminishes in elderly animals. Structural changes of muscle spindles in elderly animals probably contribute to the deterioration of the muscular function.

Distribution of GAP-43 nerve fibers in the skin of the adult human hand

Skin is an important region of somatic sensory input, and is one of the most innervated areas of the human body. In this study, we investigated in human hand skin the distribution of nervous structures immunoreactive for the growth-associated protein 43 (GAP-43) and the protein gene product 9.5 (PGP 9.5). GAP-43 is a neuronal presynaptic membrane protein that is generally considered to be a marker of neuronal plasticity. PGP 9.5 is a neuron-specific soluble protein that is widely used as general marker for the peripheral nervous system. The entire neural network of the dermis and epidermis was stained with antibody to PGP 9.5. In the dermis, there were fewer GAP-43-immunostained nerve fibers than PGP 9.5-immunostained nerve fibers, whereas in the epidermis the numbers were equal. Only some Merkel cells and Meissner corpuscles were GAP-43-immunoreactive. In conclusion, our results show that GAP-43 protein is expressed in a subset of PGP 9.5-immunoreactive nerve structures.

Early nerve regeneration after achilles tendon rupture--a prerequisite for healing? A study in the rat

Nerve regeneration during healing of Achilles tendon rupture in the rat was studied by immunohistochemistry including semi-quantitative assessment. Neuronal markers for regenerating and mature fibers, ie., growth associated protein 43 (GAP-43) and protein gene product 9.5 (PGP 9.5), respectively, were analyzed at different time points (1-16 weeks) post-rupture. In the paratenon, both the ruptured and intact contralateral tendon (control) consistently exhibited immunoreactivity to the two neuronal markers. However, in the proper tendinous tissue only the ruptured tendon showed immunoreactivity to GAP-43 and PGP 9.5. This expression was seen already at week 1 post-rupture to reach a peak at week 6 followed by a successive drop till week 16. Also the occurrence of sensory and autonomic fibers according to immunoreactivity for calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY), respectively, was analyzed. CGRP-positivity was abundantly seen from weeks 2-6 in both perivascular and sprouting free nerve endings in the proper tendon tissue undergoing healing. NPY appeared later, at weeks 6-8 post-rupture around blood vessels mainly located in the surrounding loose connective tissue. Apart from a role in vasoaction (CGRP, vasodilatory; NPY, vasoconstrictory). both neuropeptides have been implicated in fibroblast and endothelial cell proliferation required for angiogenesis. The present study shows that early healing of ruptured tendons is characterized by an orchestrated, temporal appearance of nerve fibers expressing peptides with different actions. The observed pattern of neuronal regeneration and neuropeptide expression may prove to be important for normal connective tissue healing.

Distribution and intraneuronal trafficking of a novel member of the chromogranin family, NESP55, in the rat peripheral nervous system

NESP55 (neuroendocrine secretory protein of M(r) 55000) is a novel member of the chromogranin family. In the present study, we have investigated the distribution, axonal transport and proteolytic processing of NESP55 in the peripheral nervous system. The amount of NESP55 immunoreactivity in adrenal gland was more than 240 times higher than that in the vas deferens. Double or triple immunostaining demonstrated that NESP55 immunoreactivity was highly co-localized with tyrosine hydroxylase immunoreactivity in bundles of thin axons and postganglionic sympathetic neurons; that NESP55 immunoreactivity also co-existed with vesicular acetylcholine transporter immunoreactivity in large-sized axons in sciatic nerves, and that NESP55 immunoreactivity overlapped with calcitonin gene-related peptide immunoreactivity in some large-sized axons, but NESP55 immunoreactivity was not detected in sensory neurons. Strong NESP55 immunoreactivity was found in cell bodies and axons, but it was not detectable in any terminal region by immunohistochemistry. In crush-operated sciatic nerves, NESP55 immunoreactivity could be found as early as 1 h after operation, and accumulated amounts increased substantially with time. However, NESP55 immunoreactivity was only observed in axons proximal to the crush, but none or very little distal to the crush, which was consistent with the data from radioimmunoassay. Finally, extracts of the normal and crushed sciatic nerve and vas deferens were subjected to high-performance liquid chromatography followed by radioimmunoassay. The results indicate that NESP55 is processed slowly to small peptides (GAIPIRRH) during axonal transport. NESP55 immunoreactivity was only detected in axons proximal to the crush. The data in the present study indicate that NESP55 immunoreactivity is widely distributed in adrenergic, cholinergic, and peptidergic neurons, but not in sensory neurons, and that this peptide is anterogradely, but not retrogradely, transported with fast axonal transport and slowly processed to smaller peptides during axonal transport in the peripheral nervous system.

Reciprocal age-related changes in GAP-43/B-50, substance P and calcitonin gene-related peptide (CGRP) expression in rat primary sensory neurones and their terminals in the dorsal horn of the spinal cord and subintima of the knee synovium

Age-related changes in the expression of the growth associated protein GAP-43/B-50, and the neuropeptides substance P and calcitonin gene-related peptide (CGRP) were investigated in the sensory neurones of rat dorsal root ganglia, dorsal horns of the spinal cord and subintimal knee synovium. The two time-points studied were 2 months (young adults) and 14-month (aged)-old Sprague Dawley rats. Dorsal root ganglia: In young adults, 40 and 35% of the L4-L5 dorsal root ganglion neurones were positive for GAP-43/B-50 with a 1.5 fold increase in frequency in aged rats at the L5 ganglion. GAP-43/B-50 was strongly expressed by the non-neuronal satellite cells of some medium and many large sized neurones in aged rats. There were marked reciprocal shifts between small and medium sized sensory neurones in respect to their substance P and CGRP expression profiles. Dorsal horn of the spinal cord: there was a 1.3 fold decrease of substance P at L5 level and a 1.3 and 1.5 fold decrease of CGRP at L4-L5 levels in aged rats, respectively. Synovial membrane: There was a 2.3 fold increase in GAP-43/B-50 and a 2.5 fold decrease of CGRP with no changes in substance P expression. These results indicate that (i) primary sensory neurones undergo age-related changes already in early stages of aging, (ii) aging may result in a reduction of substance P and CGRP axonal transport, and (iii) reduced numbers of CGRP containing synovial perivascular fibres may imply a deficient regulation of the synovial microvasculature and therefore metabolic homeostasis of the joint in aged subjects.

Growth-associated protein-43 immunohistochemical and ultrastructural changes in jaw muscle spindles of the rat following loss of occlusion

The effects of complete loss of occlusion on the structural and functional status of these muscle spindles were investigated by immunohistochemistry either for protein gene product 9.5 (PGP 9.5) or growth-associated protein-43 (GAP-43) by light and electron microscopy. All the upper molars of 4-week-old Wistar rats were extracted and the erupted portions of the upper and lower incisors of the same animals were cut-off at the level of the interdental papilla every other day. In a control group, immunoreactivity for GAP-43 was positive in the developing annulospiral endings of 2-week-old rats, but was not detected in any of the muscle spindles after 3 weeks of age. At 4 weeks of age, the PGP 9.5 immunostained spindles had well-differentiated annulospiral endings. Ultrastructurally, these afferent endings showed lenticular or circular profiles in cross-sections, and were differentially indented into the intrafusal-fibres. The inner surfaces of the terminals formed rather smooth myoneural junctions, while the outer surfaces were covered only by basal lamina continuous with that of the underlying intrafusal muscle fibres. After the experimental elimination of occlusal contact, GAP-43 immunoreactivity reappeared in some nerve endings of muscle spindles by 3 days, and persisted for at least 28 days. During this period, the afferent-terminals exhibited various fine structural abnormalities such as irregular outlines and invaginated neuromuscular interfaces. Some sensory-terminal (ST) profiles were completely engulfed by intrafusal-fibres. However, GAP-43 expression and ultrastructural alterations became undetectable within a week of the end of incisal cutting and the recovery of incisal-contact. These data indicate that remodelling of nerve terminals in muscle spindles, as assessed by GAP-43 expression and ultrastructural changes, occurs soon after a loss of occlusion, and ceases if incisal-contact is restored. It is concluded that possible changes in jaw muscle function, as well as a sudden loss of proprioceptive sensory input from the periodontal mechanoreceptors of molars and incisors, induce the structural reorganisation of nerve terminations in jaw muscle spindles that is associated with the appearance and disappearance of GAP-43 immunoreactivity.

LIM kinase 1 accumulates in presynaptic terminals during synapse maturation

LIM kinase 1 (LIMK1) is a cytoplasmic protein kinase that is highly expressed in neurons. In transfected cells, LIMK1 binds to the cytoplasmic tail of neuregulins and regulates the breakdown of actin filaments. To identify potential functions of LIMK1 in vivo, we have determined the subcellular distribution of LIMK1 protein within neurons of the rat by using immunomicroscopy. At neuromuscular synapses in the adult hindlimb, LIMK1 was concentrated in the presynaptic terminal. However, little LIMK1 immunoreactivity was detected at neuromuscular synapses before the 2nd week after birth, and most motoneuron terminals were not strongly LIMK1 immunoreactive until the 3rd week after birth. Thus, LIMK1 accumulation at neuromuscular synapses coincided with their maturation. In contrast, SV2, like many other presynaptic terminal proteins, can be readily detected at neuromuscular synapses in the embryo. Similar to its late accumulation at developing synapses, LIMK1 accumulation at regenerating neuromuscular synapses occurred long after these synapses first formed. In the adult ventral spinal cord, LIMK1 was concentrated in a subset of presynaptic terminals. LIMK1 gradually accumulated at spinal cord synapses postnatally, reaching adult levels only after P14. This study is the first to implicate LIMK1 in the function of presynaptic terminals. The concentration of LIMK1 in adult, but not nascent, presynaptic terminals suggests a role for this kinase in regulating the structural or functional characteristics of mature synapses.

Calcitonin gene-related peptide immunoreactivity in the hippocampus and its relationship to cellular changes following exposure to trimethyltin

Calcitonin gene-related peptide (CGRP) is a neuropeptide that is regionally regulated following peripheral insult and in central nervous system (CNS) damage models targeting limbic structures. Functional studies have shown this neuropeptide to be involved in neuronal protection and remodeling, vasodilation, immunomodulation, and apoptosis, thus making it an important constituent of the acute phase response. In the present study, we characterized the anatomic expression and distribution of CGRP immunoreactivity (CGRP-IR) after exposure to the toxin, trimethyltin (TMT). We chose this model because TMT causes dramatic changes in the endocrine system, the limbic system, particularly the hippocampus, as well as in the immune response. We have specifically focused on comparing the changes in CGRP-IR with the pattern of apoptosis (via TUNEL staining), cell-cycle activation (Ki67-IR), and in alteration in microglia (OX-42-IR) and astrocyte (gGFAP-IR) immunocytochemistry in TMT-treated hippocampus. Our results show a marked change in CGRP-IR in regions of the hippocampus that are temporally and anatomically correlated with the induction of apoptosis and activation of microglia, astrocyte, and the cell-cycle marker. Given the known effects of CGRP on these cell types and on programmed cell death elsewhere, these findings are consistent with a regional immunoregulatory/injury response role for CGRP following organotin poisoning.

B-50, the growth associated protein-43: modulation of cell morphology and communication in the nervous system

The growth-associated protein B-50 (GAP-43) is a presynaptic protein. Its expression is largely restricted to the nervous system. B-50 is frequently used as a marker for sprouting, because it is located in growth cones, maximally expressed during nervous system development and re-induced in injured and regenerating neural tissues. The B-50 gene is highly conserved during evolution. The B-50 gene contains two promoters and three exons which specify functional domains of the protein. The first exon encoding the 1-10 sequence, harbors the palmitoylation site for attachment to the axolemma and the minimal domain for interaction with G0 protein. The second exon contains the "GAP module", including the calmodulin binding and the protein kinase C phosphorylation domain which is shared by the family of IQ proteins. Downstream sequences of the second and non-coding sequences in the third exon encode species variability. The third exon also contains a conserved domain for phosphorylation by casein kinase II. Functional interference experiments using antisense oligonucleotides or antibodies, have shown inhibition of neurite outgrowth and neurotransmitter release. Overexpression of B-50 in cells or transgenic mice results in excessive sprouting. The various interactions, specified by the structural domains, are thought to underlie the role of B-50 in synaptic plasticity, participating in membrane extension during neuritogenesis, in neurotransmitter release and long-term potentiation. Apparently, B-50 null-mutant mice do not display gross phenotypic changes of the nervous system, although the B-50 deletion affects neuronal pathfinding and reduces postnatal survival. The experimental evidence suggests that neuronal morphology and communication are critically modulated by, but not absolutely dependent on, (enhanced) B-50 presence.

alpha-CGRP mRNA levels in motoneurons innervating specific rat muscles

Along with acetylcholine, motoneurons express several neuromodulatory peptides. The most extensively studied of these peptides is calcitonin gene-related peptide (CGRP). CGRP modulates the biochemical, physiological and metabolic properties of skeletal muscle primarily through activation of membrane receptors. Virtually all motor pool contain motoneurons that are immunoreactive for CGRP. The purpose of this study was to determine the proportions of motoneurons that express alpha-CGRP in motor pools innervating muscles with different motor unit compositions. These include the soleus, extensor digitorum longus, tensor fascia latae and the diaphragm muscles as well as the spinal nucleus of the bulbocavernosus. The spinal nucleus of the bulbocavernosus provides innervation to the bulbocavernosus/levator ani muscle complex and the external anal sphincter muscle. The spinal nucleus of the bulbocavernosus contained the greatest proportion of alpha-CGRP mRNA-positive motoneurons, followed in descending rank order by the tensor fascia latae, the extensor digitorum longus, the soleus and the diaphragm motor pools. In addition, significant differences between motor pools were observed in the mean relative alpha-CGRP mRNA level among those motoneurons expressing alpha-CGRP. The highest mean relative alpha-CGRP mRNA level was observed in soleus and the extensor digitorum longus motor pools; followed in descending rank order by the tensor fascia latae, the diaphragm and the spinal nucleus of the bulbocavernosus. We have previously shown that muscle contractile inactivity increases the number of motoneurons that express alpha-CGRP and in the relative mRNA levels. The results of the present study suggest that the proportion of motoneurons within a motor pool that express alpha-CGRP may be closely related to the contractile activity (i.e. activation history) of the target muscle.

Ultrastructural localization of B-50/growth-associated protein-43 to anterogradely transported synaptophysin-positive and calcitonin gene-related peptide-negative vesicles in the regenerating rat sciatic nerve

The growth-associated protein-43/B-50 (B-50/GAP-43) is conveyed from the neuronal soma into the axon by fast axonal transport and moved to the nerve terminal. To visualize and determine the type of vesicles by which B-50/GAP-43 is anterogradely transported in the regenerating rat sciatic nerve, we have investigated Lowicryl HM20 embedded nerve pieces dissected from the proximal side of a collection ligature. Ultrastructurally, numerous vesicular profiles of various sizes, tubules and mitochondria were seen to accumulate proximal to the collection ligature. Both, in unmyelinated and myelinated axons, B-50/GAP-43 immunoreactivity was associated with vesicular profiles which had a diameter of 50 nm. A fraction of the B-50/GAP-43 label co-localized with the small vesicle marker synaptophysin. Co-localization of B-50/GAP-43 was not detected with the large dense-core vesicle marker calcitonin gene-related peptide. These results indicate that, in rat sciatic nerve axons, B-50/GAP-43 is anterogradely transported in small 50 nm vesicles of the constitutive pathway. These transport vesicles were distinguished in two types. We suggest that one type carrying, both, B-50 GAP-43 and synaptophysin has as destination the nerve terminal, whereas the second type, which only contains B-50/GAP-43 and no synaptophysin, may be primarily targeted to the axolemma for local membrane fusion.

Increase of B-50/GAP-43 immunoreactivity in uninjured muscle nerves of MDX mice

Lack of dystrophin in mdx mice leads to muscle fibre degeneration followed by the formation of new myofibres. This degeneration-regeneration event occurs in clusters. It is accompanied by inflammation and remodelling of the intramuscular terminal nerve fibres. Since the growth-associated protein B-50/GAP-43 has been shown to be involved in axonal outgrowth and synaptic remodelling following neuronal injury, we have investigated the presence of B-50 in gastrocnemius and quadriceps muscles of mdx mice. Using immunocytochemistry we demonstrate increased presence of B-50 in terminal nerve branches at motor endplates of mdx mice, particularly in the clusters of de- and regenerating myofibres. In comparison, the control mice displayed no B-50 immunoreactivity in nerve fibres contacting motor endplates. Our findings indicate that during axonal remodelling and collateral sprouting the B-50 level in the terminal axon arbours is increased although there is no direct injury to the motoneurons. We suggest that the degenerating target and/or the inflammatory reaction induces the increased B-50 level in the motoaxons. The increased B-50 may be important for sprouting of the nerve fibres and re-establishment of synaptic contacts, and in addition, for maturation and survival of the newly formed myofibres.

The increase in B-50/GAP-43 in regenerating rat sciatic nerve occurs predominantly in unmyelinated axon shafts: a quantitative ultrastructural study

The growth-associated protein B-50/GAP-43 is thought to play a crucial role in axonal growth. We investigated, by quantitative immunoelectron microscopy, whether there are differences in the subcellular distribution of B-50 in unmyelinated and myelinated axons of intact and regenerating sciatic nerves. Adult rats received an unilateral sciatic nerve crush and were euthanized 8 days later. Nerve pieces proximal from the crush site were embedded, and B-50 was visualized by specific B-50 antibodies and immunogold detection in ultrathin sections. The density of B-50 at the plasma membrane of unmyelinated axon shafts was significantly increased in the ipsilateral regenerating nerve in comparison to that of the contralateral intact nerve. In contrast, there was no significant difference in the B-50 density at the axolemma of myelinated regenerating and intact axon shafts. In the contralateral intact nerve, more B-50 was associated with the axolemma of unmyelinated axons than with the plasma membrane of myelinated axons. The density of axoplasmic B-50 was similar in intact unmyelinated and myelinated axon shafts, but was higher in regenerating nerve than in intact nerve. This suggests that enhanced axonal transport of B-50 occurs during axon outgrowth. Our study demonstrates a differential subcellular distribution of B-50 in unmyelinated and myelinated axon shafts in both the intact and regenerating sciatic nerve, indicating a differential inducible capacity for remodeling of the axon shafts.

Expression of myosin heavy chain isoforms and myogenesis of intrafusal fibres in rat muscle spindles

This review concerns the pattern of expression and regulation of myosin heavy chain (MHC) isoforms in intrafusal fibres of rat muscle spindles detected by immunocytochemistry. The three types of intrafusal fibres--nuclear bag1, nuclear bag2, and nuclear chain fibres--are unique in co-expressing several MHCs including special isoforms such as slow tonic and alpha cardiac-like MHC and isoforms typical of muscle development, such as embryonic and neonatal MHC. The distinct intrafusal fibre types appear sequentially during rat hind limb development, the nuclear bag2 precursors being first identifiable at 17-18 days in utero as the only primary myotubes expressing slow tonic MHC. Sensory innervation is required for the expression of "spindle-specific" MHC isoforms. Motor innervation contributes to the diversity in distribution of the different MHCs along the length of the nuclear bag fibres. It is suggested that unique populations of myoblasts are destined to become intrafusal fibres during development in the rat hind limb muscles and that the regional heterogeneity in MHC expression is related both to sensory and motor innervation and to the properties of the myoblast lineages. These distinct features make intrafusal fibres an attractive in situ model for investigating myogenesis, myofibrillogenesis, and the mechanisms regulating MHC expression.

GAP-43 and its relation to autonomic and sensory neurons in sciatic nerve and gastrocnemius muscle in the rat

The presence of the growth-associated protein, GAP-43, in rat sciatic nerve and gastrocnemius muscle was studied, using indirect immunofluorescence, in lumbar sympathectomized and sham-sympathectomized rats. To study fast axonal transport and accumulation of immunogenic GAP-43, the sciatic nerves were crush operated, 6 h before perfusion fixation. In sections of normal, crushed sciatic nerve GAP-43-like immunoreactivity (LI) rapidly accumulated, on both sides of the crushes, in medium and thin sized axons. In double immunostaining experiments, GAP-43-LI was mainly colocalized with tyrosine hydroxylase (TH)-LI, or neuropeptide Y (NPY)-LI, markers of sympathetic nerves. In some axons, GAP-43-LI was colocalized with Substance P (SP)-LI. In perivascular nerve terminals in the gastrocnemic muscle, strong GAP-43-immunofluorescence was observed, in most cases colocalized with TH-LI, but in some terminals with SP-LI. Three days after lumbar sympathectomy (removal of the L1-L4 sympathetic ganglia bilaterally), TH-LI and NPY-LI positive axons in the sciatic nerve were reduced in number by more than 90%. GAP-43-LI positive axons were reduced by about 50%. In the gastrocnemic muscle, some GAP-43-LI positive terminals, but very few TH-LI positive nerve fibres, were found around blood vessels. No further changes were seen 8 days after sympathectomy. SP-LI in axons in the sciatic nerve and in perivascular nerve terminals of the gastrocnemic muscle, did not change after sympathectomy; most of these axons also contained GAP-43-LI. S-100-LI was present periaxonally in the sciatic nerves, but it did not colocalize with GAP-43, indicating that Schwann cells contained no GAP-43-LI in these experiments. The results show that, in normal adult rats, GAP-43-LI is mainly present in sympathetic and sensory nerve fibers in sciatic nerve and in perivascular nerve terminals. The peptide is axonally transported, mainly in sensory and adrenergic axons.

Growth-associated protein-43 and protein gene-product 9.5 innervation in human pancreas: changes in chronic pancreatitis

Growth-associated protein-43, an established marker of neuronal plasticity during development and in injury, was used to characterize innervation in the normal human pancreas and changes in chronic alcohol-induced pancreatitis by using light microscopic immunocytochemistry and computer-assisted image analysis. Immunostaining for the pan-neuronal marker protein gene-product 9.5 served as a reference for the characterization of total innervation in both groups. In normal human pancreas, strong protein gene-product 9.5 immunostaining revealed all nerve fibres in nerve trunks, all neuronal cell bodies and the entire parenchymal innervation. In contrast, growth-associated protein-43 immunoreactivity was restricted to a few nerve fibres in interlobular nerve trunks and to fine varicose nerve fibres supplying the parenchyma, blood vessels, pancreatic ducts and intrinsic ganglia. In cell bodies of intrinsic neurons, growth-associated protein-43 immunoreactivity was absent or extremely faint. In chronic pancreatitis, the protein gene-product 9.5 innervation exhibited region-specific changes. In areas with reduced parenchyma, the protein gene-product 9.5 innervation was sparse. In fibrotic regions, which are characteristic for advanced stages of chronic pancreatitis, enlarged nerve trunks showing neuroma-like formations were heavily stained for protein gene-product 9.5. In fibrotic tissue, protein gene-product 9.5-containing nerve fibres were extremely rare. The growth-associated protein-43 innervation in chronic pancreatitis was characterized by a dramatic increase, which was most pronounced in the enlarged nerve trunks. Such nerve trunks were frequently surrounded by infiltrates of immune cells, which in some cases formed follicle-like structures. Digital image analysis of adjacent sections and double fluorescence immunocytochemistry revealed that growth-associated protein-43 immunoreactivity was present in the vast majority of protein gene-product 9.5-immunoreactive nerve fibres. In contrast to the normal pancreas, a major subpopulation of intrinsic neurons immunostained for growth-associated protein-43. The expression of growth-associated protein-43 in the terminal fields of pancreatic nerve suggests that the innervation of the normal human pancreas undergoes continual and toposelective remodelling. The increase in the density of growth-associated protein-43 immunoreactive nerve fibres in enlarged nerve trunks paralleled by augmented expression of growth-associated protein-43 in intrinsic neurons and reduced parenchymal growth-associated protein-43-immunoreactive innervation underline the dramatic plasticity of pancreatic innervation in chronic pancreatitis.(ABSTRACT TRUNCATED AT 400 WORDS)

GAP 43-like immunoreactivity in normal adult rat sciatic nerve, spinal cord, and motoneurons: axonal transport and effect of spinal cord transection

Using immunofluorescence and cytofluorimetric scanning techniques in the rat, the fast anterograde and retrograde axonal transport of growth-associated protein-43-like immunoreactivity in normal sciatic nerves, and after spinal cord transection in the lower thoracic region, were investigated. Spinal roots and motor endplates in the peroneal muscles were also studied. For comparison, anti-synaptophysin (p38) was used. In intact adult animals, the amounts of immunoreactive growth-associated protein-43 increased linearly, both proximally and distally to the crush site, between 1 and 24 h after crushing the sciatic nerve. The accumulations were present in thick as well as in thin axons. Distal accumulations in the sciatic nerve were about 40-60% of the proximal amounts, indicating a recycling of organelles with growth-associated protein-43-like immunoreactivity. During the week after spinal cord transection, no clear changes were observed; the anterograde transport of growth-associated protein-43-like immunoreactivity showed a tendency to decrease at day 1 and then a tendency to increase, reaching 120% of control at seven days (not significant). Transported p38-like immunoreactivity showed similar but smaller changes. In the lumbar spinal cord gray matter many nerve terminals with growth-associated protein-43-like immunoreactivity were seen in intact animals. After spinal transection, these terminals gradually decreased, suggesting that they belonged to descending pathways. However, p38-positive terminals were not obviously decreased. After crushing ventral and dorsal roots, accumulations of pf growth-associated protein-43-like immunoreactivity were present in thick axons in the ventral roots and in thin to medium-sized axons in the dorsal roots. In peroneal muscles, growth-associated protein-43-like immunoreactivity was present in some (but not all) motor endplates in all groups. These results indicate that: (i) growth-associated protein-43 is normally present in nerve terminals of many descending projections of the spinal cord; (ii) growth-associated protein-43-like immunoreactivity is expressed and bidirectionally transported in neurons (motor as well as sensory) of normal sciatic nerves; (iii) growth-associated protein-43-like immunoreactivity is present in some adult motor endplates; and (iv) inhibited supraspinal input causes minor, if any, alterations--paralleled by p38--in axonal transport of growth-associated protein-43-like immunoreactivity.