Changes In Innervation Pattern Research Articles

Dirk Pette, remembered for his pioneering muscle research.

It is with great sadness that we learned of the passing of Prof. Dr. Dr. h.c. Dirk Pette. He passed away suddenly and unexpectedly on June 4, 2022. Dirk was an outstanding professor of biochemistry at the University of Konstanz, Germany and an internationally renowned researcher in the field of skeletal muscle biology. His research on electrical stimulation has had a profound impact on our understanding of myofiber type specification and the enormous adaptive potential of skeletal muscle. Under Dirk's leadership, new biological questions in the field of neuromuscular biology have developed into multidisciplinary approaches using advanced physiological, cell biological, and biochemical techniques. Dirk's research laboratory was frequently visited by a large number of national and international collaborators who familiarized themselves with the technically demanding stimulation protocols and bioanalytical techniques to study the intricate details of the highly complex process of fast-to-slow muscle transitions. Importantly, fundamental studies on the physiological effects of changes in innervation patterns on muscle phenotype have provided the scientific evidence base for a variety of innovative clinical applications. The skeletal muscle research community has lost one of its leading figures and an outstanding teacher of protein biochemistry. He leaves an inspiring legacy in the field of basic and applied myology. Dirk will be missed by his colleagues and by many students of neuromuscular biology and beyond.

Abnormal Reinnervation of Denervated Areas Following Nerve Injury Facilitates Neuropathic Pain.

An injury to peripheral nerves leads to skin denervation, which often is followed by increased pain sensitivity of the denervated areas and the development of neuropathic pain. Changes in innervation patterns during the reinnervation process of the denervated skin could contribute to the development of neuropathic pain. Here, we examined the changes in the innervation pattern during reinnervation and correlated them with the symptoms of neuropathic pain. Using a multispectral labeling technique—PainBow, which we developed, we characterized dorsal root ganglion (DRG) neurons innervating distinct areas of the rats’ paw. We then used spared nerve injury, causing partial denervation of the paw, and examined the changes in innervation patterns of the denervated areas during the development of allodynia and hyperalgesia. We found that, differently from normal conditions, during the development of neuropathic pain, these areas were mainly innervated by large, non-nociceptive neurons. Moreover, we found that the development of neuropathic pain is correlated with an overall decrease in the number of DRG neurons innervating these areas. Importantly, treatment with ouabain facilitated reinnervation and alleviated neuropathic pain. Our results suggest that local changes in peripheral innervation following denervation contribute to neuropathic pain development. The reversal of these changes decreases neuropathic pain.

Immune cell infiltration and growth-associated protein 43 expression correlate with pain in chronic pancreatitis

BACKGROUND & AIMS: Changes in innervation pattern and neuropeptide content have been shown in chronic pancreatitis (CP), including increased neuronal expression of growth-associated protein 43 (GAP-43). We used GAP-43 as an established marker of neuronal plasticity and correlated histological findings with pain scores of patients with CP. METHODS: In tissue samples from 29 patients with CP, the parenchyma- fibrosis ratio, degree of perineural immune cell infiltration, and neuronal GAP-43 immunoreactivity were determined by digitized morphometry and correlated with individual pain scores. RESULTS: In CP, GAP-43 was significantly increased in pancreatic nerve fibers and intrinsic neurons. GAP-43 expression correlated with individual pain scores. The infiltration of pancreatic nerves by immune cells was significantly correlated with the intensity of pain. Pain scores correlated neither with the degree of pancreatic fibrosis nor with the duration of the disease. CONCLUSIONS: The results suggest that infiltration of pancreatic nerves by immune cells and neuronal plasticity are pathogenic factors for the generation of pain, whereas the degree of pancreatic fibrosis has no major impact on pain in CP. (Gastroenterology 1997 May;112(5):1648-55)

Regeneration of facial nerve after hypoglossal facial anastomosis: an animal study.

Hypoglossal-facial nerve anastomosis was carried out in 20 adult guinea pigs. Electromyographic responses of orbicularis oculi muscle evoked by blink reflex were recorded 2, 4, and 6 months after surgery. Then the anastomotic site was reopened, and a segment of buccal branch and the anastomotic trunk were resected for detailed histologic study. Regenerated axons were counted and the cross-sectional area of axons and fasciculi was measured. Data obtained from both blink reflex measurement and histologic study demonstrate a good quality of regeneration of the facial nerve from the hypoglossal nerve completed 6 months after the operation. In addition a new nerve bundle was regenerated from the proximal stump of the facial nerve connecting to the anastomotic site in 80% of the animals. Postoperative change in innervation pattern of the facial nerve was also illustrated.

Regeneration of facial nerve after hypoglossal facial anastomosis: An animal study

Hypoglossal-facial nerve anastomosis was carried out in 20 adult guinea pigs. Electromyographic responses of orbicularis oculi muscle evoked by blink reflex were recorded 2, 4, and 6 months after surgery. Then the anastomotic site was reopened, and a segment of buccal branch and the anastomotic trunk were resected for detailed histologic study. Regenerated axons were counted and the cross-sectional area of axons and fasciculi was measured. Data obtained from both blink reflex measurement and histologic study demonstrate a good quality of regeneration of the facial nerve from the hypoglossal nerve completed 6 months after the operation. In addition a new nerve bundle was regenerated from the proximal stump of the facial nerve connecting to the anastomotic site in 80% of the animals. Postoperative change in innervation pattern of the facial nerve was also illustrated.

Ultrastructural plasticity of the dentate gyrus granule cells following recurrent limbic seizures: II. Alterations in somatic synapses.

Hilus lesion-induced recurrent limbic seizures cause a dramatic increase in the numbers of somatic spines on dentate gyrus granule cells in the adult rat. Somatic spines are maximally increased 3 h after the initiation of seizures at which time many of these spines form synapses. The present quantitative electron microscopic study assessed the numbers and types of synapses present on the granule cell perikarya and somatic spines of control and experimental seizure rats with the goal of determining if newly elaborated somatic spines arise at the site of pre-existing synapses or are associated with new innervation. Experimental rats were sacrificed 5 h after hilar lesion placement (or 3 h after seizure onset). In both control and hilus-lesioned (HL) rats, 15-20% of the somatic spines could be seen to form synaptic contacts within a single plane of section; these synapses were almost exclusively of the asymmetric type. With the increased incidence of spines in experimental-seizure rats, there was a 6.25-fold greater number of spine synapses in HL versus control rats. There was, in addition, a 60% decrease in the number of asymmetric synapses occurring directly on the granule cell perikarya but no change in the total (spine plus somatic) number of asymmetric synapses. Although few asymmetric synapses were associated with spines in control tissue, 60-70% of asymmetric synapses were associated with spines in experimental-seizure tissue. In addition, in hilus lesion rats symmetric somatic synapses were increased by 20% on cells in deep stratum granulosum resulting in a dissolution of the superficial-to-deep innervation gradient present in the untreated rat. These findings support the conclusion that spines induced by seizure activity form at the site of pre-existing asymmetric synapses on the granule cells and demonstrate that brief seizure episodes can rapidly induce marked changes in innervation patterns in the adult brain.

Changes in septo-hippocampal projections after lateral entorhinal or combined entorhinal-raphé lesions as studied by anterograde tracing methods

Septal and entorhinal projections to the hippocampus show a considerable overlap in their target structures in the molecular layer of the dentate gyrus (DG) and stratum lacunosum-moleculare of the cornu ammonis (CA). Employing anterograde tracing methods, it was investigated in which way the morphological pattern of the septohippocampal projections were influenced by lateral entorhinal cortex (LEA) lesions. Anterograde filling neurons of from soma to axonal terminals with Phaseolus vulgaris leucoagglutinin (PHA-L) revealed lesion-induced changes in innervation patterns in the DG but not in CA fields. LEA lesions provoke an impressive shift of septo-dentate projections from a predominant middle molecular layer innervation to the outer molecular layer, whereas septal projections to the CA remain unchanged. Comparison with concurrent acetylcholinesterase (AChE) staining and immunocytochemical demonstration of choline acetyltransferase (ChAT) confirm the cholinergic nature of this plasticity response. This response was equally strong in unilateral or bilateral damage to the LEA and was neither enhanced nor inhibited by simultaneous injury to the median raphé nuclei.

Motor unit estimates in the biceps-brachialis in amyotrophic lateral sclerosis.

A newly developed technique for estimating the number of motor units in the biceps-brachialis muscles and for studying the innervation patterns of motor units in the same muscles has been applied to the study of 17 patients with amyotrophic lateral sclerosis (ALS). Although severe motor unit losses were seen in many ALS cases, in most there were clear indications of increases in innervation densities, linked potentials, and blocking. This technique provides a powerful new tool for quantitatively assessing the extent of motor unit losses and the accompanying changes in innervation patterns in ALS.

Increased density of perivascular nerves to the major cerebral vessels of the spontaneously hypertensive rat: differential changes in noradrenaline and neuropeptide Y during development

Fluorescence and immunohistochemical techniques were used to study the pattern and density of perivascualr nerves containing noradrenaline (NA) and neuropeptide Y (NPY) supplying the major cerebellar of 4-, 6-, 8- and 12-wee-κ-old spontaneously hypertensie rats (SHR) and normotenive Wistar (WIS) controls. Levels of NA and NPY in the superior cervical ganglia were measured. The density of nerves containing NA and NPY was greater in the hypertensive animals at all ages studied. However, the developmental changes in the density of innervation showed similar trends in both SHR and WIS groups. With few exceptions, there was a significant increase in the density of nerves containing NA from 4 to 6 weeks and from 8 to 12 weeks of age. This was in contrast to a low expression, and in some vessels a significant decrease in the number of NPY-containing nerves from 4 to 6 weeks. The density of nerve fibres containing NPY increased significantly in almost all vessels between 6 and 8 weeks of age and then stabilized. Thus there is a differential time course for the appearance of NA and NPY during development. Furthermore, the hyperinnervation of cerebral vessels in SHR by nerves containing NA and NPY precedes the onnset of hypertension and associated medial hypertrophy. High-performance liquidchromatography and enzyme-linked immunosorbant assays show that the NA and NPY content of the superior cervical ganglion do not reflect the changes in innervation pattern seen in the fibres in the cerebral arteries. This tends to support the view that a local neuovascular mechanism in involved in the maintenance of hypertension. The possibility that increase in NPY as well as NA in cerebral periivascular nerves of hypertensive animals is involved in the protection of the blood-brain against oedema and cerebral haemorrhage is raised.

Inhibition of acetylcholinesterase accelerates axon terminal withdrawal at the developing rat neuromuscular junction.

In developing skeletal muscles, the rate at which superfluous innervation is lost from the endplates depends on the general level of neuromuscular activity. Whether it is activity of the presynaptic or postsynaptic structures (or both) that is critical is not well established. In this work, we transitorily inhibited the AChE of soleus muscle in postnatal rats, in order to increase postsynaptic activity, without directly altering activity of the nerve terminals. We then followed the time course of disappearance of axon terminals from the endplates of treated and normal muscles, using electron-microscope techniques. Three hours after inhibition of AChE, the muscle fibres exhibited local supercontracture and ultrastructural damage in the region of the endplate, consistent with local elevation of Ca2+ levels. At the same time, small electron-opaque vesicles, apparently of muscular origin, appeared in the synaptic cleft. The nerve terminals, however, were entirely normal in number and appearance. One day after treatment, endplates of esterase-inhibited muscles showed accelerated loss of nerve terminals, compared to endplates of normally developing muscles. No further loss of nerve terminals occurred, once AChE activity returned at the endplate. These results suggest that the rate at which superfluous nerve terminals retract from the developing neuromuscular junction is regulated by the level of activation of the muscle. It seems likely that activity of postsynaptic sites may similarly regulate changes in innervation patterns, in other developing or adapting neuro-neuronal or neuro-effector systems.

The distribution of cholinergic and adrenergic nerves in the mammalian epididymis: a comparative histochemical study.

AbstractThe distribution of cholinergic and adrenergic nerves in the epididymis was studied in the dog, cat, rat and rabbit using specific histochemical techniques for acetylcholinesterase and norepinephrine. Both cholinergic and adrenergic nerves are associated with tunical, septal and interstitial blood vessels, run independently in the intertubular connective tissue, and surround the epididymal tubules.Throughout the epididymis there are rich adrenergic and cholinergic perivascular plexuses. The distribution and pattern of interstitial and peritubular cholinergic and adrenergic nerves vary in the three anatomical regions of the epididymis in different animals. In the dog and cat the nerves form plexuses in relation to the ductuli efferentes in the caput, and run as isolated fibers in the corpus epididymidis. In the rat and rabbit there are no interstitial or peritubular nerves in the caput and proximal part of the corpus and few nerves in the distal part of the corpus. The cauda epididymidis is the most richly innervated part of the epididymis. Both interstitial and peritubular cholinergic and adrenergic nerves form plexuses of nerve fibers and bundles, which progressively become more prominent and more intricate as the cauda is traced distally towards its junction with the vas deferens. These changes in innervation pattern follow the distalward increase in thickness of the muscular wall of the ductus epididymidis and are noted in all animals studied.Ganglia are encountered only in the caput epididymidis in the cat. Cholinergic and adrenergic epithelial fibers are present in the caput and cauda but not in the corpus epididymidis. In the cauda they penetrate through most of the thickness of the epithelium; the cholinergic fibers in this region form a loose intra‐epithelial plexus.