Sensory Terminations Research Articles

A Call for Discovery and Therapeutic Development for Cutaneous Neurofibromas

A Call for Discovery and Therapeutic Development for Cutaneous Neurofibromas

Role of antitussive agents in the treatment of acute respiratory viral infections and influenza

Viral upper respiratory infection (VURI)-associated acute cough is the most common symptom worldwide among children and adults. It causes serious economic and social problems both for individual patients, patients’ families, and the health care system as a whole. There is still no effective pharmacological agent capable of interfering with all the main pathophysiological mechanisms involved in VURI-associated acute cough. This circumstance partly explains the increased prevalence of the prolonged course of acute respiratory infections, when the cough takes on the features of subacute or post-infectious course. The pathophysiology of this symptom is being actively investigated to optimize the treatment of cough. A viral infection provokes an acute cough induced by various irritative stimuli, the main one being secretions from the respiratory tract, which directly acts on reflexogenic areas of the mucosa. Inflammatory mediators also play an important role, acting on the peripheral sensory terminations of airways. Inflammatory mediators also induce post-infectious bronchial hyperreactivity, which is an important component of the pathogenesis of post-infectious cough. Recently, researchers are becoming increasingly interested in the role of the voluntary or conscious cough component, which is implemented due to the cortical response to afferent information from the receptors of the upper respiratory tract.This hypothesis explains the ineffectiveness of central antitussive agents in patients with viral infection-associated dry cough and expands the possibilities of peripheral antitussive agents represented by levodropropizine. In addition to the action on nerve endings, the agent also affects inflammatory mediators, which enhances its ability to break the “vicious circle” of this symptom, prevents the development of post-infectious cough and promotes rehabilitation of the bronchial tree. The efficacy and safety of levodropropizine has been demonstrated in clinical trials in both children and adults.

Neuroprotective effects of rutin on ASH neurons in Caenorhabditis elegans model of Huntington’s disease

ABSTRACT Huntington’s disease (HD) is an autosomal dominant, progressive neurodegenerative disease. It occurs due to a mutated huntingtin gene that contains an abnormal expansion of cytosine-adenine-guanine repeats, leading to a variable-length N-terminal polyglutamine (polyQ) chain. The mutation confers toxic functions to mutant huntingtin protein, causing neurodegeneration. Rutin is a flavonoid found in various plants, such as buckwheat, some teas, and apples. Our previous studies have indicated that rutin has protective effects in HD models, but more studies are needed to unravel its effects on protein homeostasis, and to discern the underlying mechanisms. In the present study, we investigated the effects of rutin in a Caenorhabditis elegans model of HD, focusing on ASH neurons and antioxidant defense. We tested behavioral changes (touch response, movement, and octanol response), measured neuronal polyQ aggregates, and assessed degeneration using a dye-filling assay. In addition, we analyzed expression levels of heat-shock protein-16.2 and superoxide dismutase-3. Overall, our data demonstrate that chronic rutin treatment maintains the function of ASH neurons, and decreases the degeneration of their sensory terminations. We propose that rutin does so in a mechanism that involves antioxidant activity by controlling the expression of antioxidant enzymes and other chaperones regulating proteostasis. Our findings provide new evidence of rutin’s potential neuroprotective role in the C. elegans model and should inform treatment strategies for neurodegenerative diseases and other diseases caused by age-related protein aggregation.

The evolution and multi-molecular properties of NF1 cutaneous neurofibromas originating from C-fiber sensory endings and terminal Schwann cells at normal sites of sensory terminations in the skin.

In addition to large plexiform neurofibromas (pNF), NF1 patients are frequently disfigured by cutaneous neurofibromas (cNF) and are often afflicted with chronic pain and itch even from seemingly normal skin areas. Both pNFs and cNF consist primarily of benign hyperproliferating nonmyelinating Schwann cells (nSC). While pNF clearly arise within deep nerves and plexuses, the role of cutaneous innervation in the origin of cNF and in chronic itch and pain is unknown. First, we conducted a comprehensive, multi-molecular, immunofluorescence (IF) analyses on 3mm punch biopsies from three separate locations in normal appearing, cNF-free skin in 19 NF1 patients and skin of 16 normal subjects. At least one biopsy in 17 NF1 patients had previously undescribed micro-lesions consisting of a small, dense cluster of nonpeptidergic C-fiber endings and the affiliated nSC consistently adjoining adnexal structures—dermal papillae, hair follicles, sweat glands, sweat ducts, and arterioles—where C-fiber endings normally terminate. Similar micro-lesions were detected in hind paw skin of mice with conditionally-induced SC Nf1-/- mutations. Hypothesizing that these microlesions were pre-cNF origins of cNF, we subsequently analyzed numerous overt, small cNF (s-cNF, 3–6 mm) and discovered that each had an adnexal structure at the epicenter of vastly increased nonpeptidergic C-fiber terminals, accompanied by excessive nSC. The IF and functional genomics assays indicated that neurturin (NTRN) and artemin (ARTN) signaling through cRET kinase and GFRα2 and GFRα3 co-receptors on the aberrant C-fiber endings and nSC may mutually promote the onset of pre-cNF and their evolution to s-cNF. Moreover, TrpA1 and TrpV1 receptors may, respectively, mediate symptoms of chronic itch and pain. These newly discovered molecular characteristics might be targeted to suppress the development of cNF and to treat chronic itch and pain symptoms in NF1 patients.

Risk factors for occurrence of failed interscalene brachial plexus blocks for shoulder arthroscopy using 20 mL 0.5% ropivacaine: a randomised trial.

Adequate pain management after arthroscopic procedures improves patients' satisfaction with the performed procedure, as well as facilitating early rehabilitation. The aim of the current randomised, prospective clinical study was to assess the influence of anthropometric parameters and the interscalene brachial plexus block (IBPB) technique on the quality of post-operational analgesia. 109 randomly selected patients of ASA I-III status were scheduled for elective shoulder arthroscopy. Reasons for non-inclusion were as follows: neurological deficit in the upper arm; allergies to amide Las; coagulopathy; and pregnancy. The patients received 20 mL of 0.5% ropivacaine for an ultrasound (US)-guided IBPB (group U), peripheral nerve stimulation (PNS)-confirmation IBPB (group N), or US-guided, PNS-confirmed IBPB (dual guidance; group NU). We observed that the studied groups did not differ in mean time of sensory and motor block terminations and, surprisingly, in each group in individual cases the sensory block lasted up to 890-990 minutes providing satisfactory long-lasting post-operational analgesia in patients receiving IBPB. We observed a negative correlation between BMI and termination of the motor block and a positive correlation between age and termination of the sensory block in patients receiving US-guided IBPB (group U) in comparison with the two other groups. We found a positive correlation between the male gender and termination of the motor block in patients receiving PNS-guided IBPB (group N) in comparison with two other groups. In our study, patients received satisfactory analgesia in the post-operational period no matter what technique was used regardless of their age, gender or potentially uncommon anthropometry.

"Babysitting" procedures in proximal nerve trunk injuries: two case reports and a review

One of the most important goals in treating proximal nerve injuries is to maintain the function of distal effectors during axonal regeneration. Babysitting, that is, connecting the injured nerve to a healthy trunk provides a bypass for distal neural regeneration or reactivation. It avoids degeneration of sensory and motor terminations, with minimal donor nerve damage. We present a technique where a nerve graft is used between ulnar and median nerve through two end-to-side sutures in the distal third of the forearm, in two different cases of proximal ulnar nerve injury. Both patients were young manual workers, the former suffered a total nerve disruption proximal to the elbow following a car accident and the latter suffered a perineurial scar from a high voltage injury at the proximal third of the forearm. The proximal injury was grafted with a sural nerve in the former and treated by neurolysis in the latter. Results were graded by the Highet-Zachary scale for both sensory and motor recovery. The outcomes of our series were compared to six other case reports in the literature (including median nerves) treated with this technique. Both clinical and experimental data show that babysitting effectively protects distal effectors.

Sensory Innervation of the Nonspecialized Connective Tissues in the Low Back of the Rat

Chronic musculoskeletal pain, including low back pain, is a worldwide debilitating condition; however, the mechanisms that underlie its development remain poorly understood. Pathological neuroplastic changes in the sensory innervation of connective tissue may contribute to the development of nonspecific chronic low back pain. Progress in understanding such potentially important abnormalities is hampered by limited knowledge of connective tissue’s normal sensory innervation. The goal of this study was to evaluate and quantify the sensory nerve fibers terminating within the nonspecialized connective tissues in the low back of the rat. With 3-dimensional reconstructions of thick (30–80 µm) tissue sections we have for the first time conclusively identified sensory nerve fiber terminations within the collagen matrix of connective tissue in the low back. Using dye labeling techniques with Fast Blue, presumptive dorsal root ganglia cells that innervate the low back were identified. Of the Fast Blue-labeled cells, 60–88% also expressed calcitonin gene-related peptide (CGRP) immunoreactivity. Based on the immunolabeling with CGRP and the approximate size of these nerve fibers (≤2 µm) we hypothesize that they are Aδ or C fibers and thus may play a role in the development of chronic pain.

Growth-associated protein-43 immunoreactivity in human oral mucosa in dentate subjects, in edentulous patients and after implant-anchored rehabilitation.

This study investigates expression of the neural growth-associated protein 43 (GAP-43) in the oral mucosa of (A) normal dentate subjects, (B) edentulous patients rehabilitated with conventional denture and (C) those rehabilitated with mandibular implant-retained overdentures (MIR-OVD), in the long term. This study evaluates morphological changes in the distribution and representation of sensory terminations and corpuscles in the alveolar mucosa under the action of different masticatory or prosthetic loads, in the three clinical groups. GAP-43 immunoreactivity (-ir) was compared with the distribution of nerves fibres in the mucosa, as visualised using anti-protein gene product 9.5 (PGP 9.5), a general marker for peripheral nerves and terminals. GAP-43-ir was found to be highly expressed in the corium and submucosa in specimens from edentulous subjects wearing conventional denture and presenting a reduced number of PGP 9.5-ir nerves in the mucosa, but not in specimens from control subjects or patients wearing MIR-OVD, which on the contrary show a higher number of PGP 9.5-ir mucosal sensory fibres. As the mucosa under traditional denture has been shown to possess reduced innervation and the histological aspect of chronic overloading, these results may be considered indicative of a tentative induction to nerve re-growth in the under-innervated epithelium, or as a response to chronic inflammation. The detection of GAP-43-ir suggests that human oral mucosa presents signs of potential nerve plasticity also in the elderly, and that the type of rehabilitation and the condition of masticatory load transfer to the mucosa have important effects on the nerves underneath.

The effects of long-standing limb loss on anatomical reorganization of the somatosensory afferents in the brainstem and spinal cord

We examined the terminations of sensory afferents in the brainstem and spinal cord of squirrel monkeys and prosimian galagos 4-8 years after a therapeutic forelimb or hindlimb amputation within 2 months of birth. In each animal, the distributions of labeled sensory afferent terminations from remaining body parts proximal to the limb stump were much more extensive than in normal animals. These sprouted afferents extended into the portions of the dorsal horn of the spinal cord as well as the cuneate and external cuneate nuclei of the brainstem (forelimb amputees) or spinal Clarke's column (hindlimb amputee) related to the amputated limb. Such reorganization in sensory afferents along with reorganization of the motor efferents to muscles (Wu and Kaas, J Neurosci 19 : 7679-7697, 1999, Neuron 28 : 967-978, 2000) may provide a basis for mislocated phantom sensations of missing forelimb movements accompanying actual shoulder movements during cortical stimulation or movement imagery in patients with amputations.

Innervation of the human epidermis. A historical review.

Skin biopsy represents an attractive technique to evaluate the extensive innervation of human epidermis, as demonstrated by the immunoreactivity of the intra-epidermal nerve fibers to the marker protein gene product 9.5. Intra-epidermal nerve fibers can be reliably quantified, and their density correlates with both the presence and the severity of sensory neuropathy. The first description of nerve fibers within human epidermis was published by Paul Langerhans. However, the limitations imposed by the relatively insensitive staining methods led several investigators working during the following century to deny or minimize their existence. The author reviews the assumptions and the striking discrepancies emerging from the wide literature on cutaneous sensory terminations since the late nineteenth century and highlights the new developments emerging from the most recent works.

A Role for Collapsin-1 in Olfactory and Cranial Sensory Axon Guidance

Collapsin-1 is a member of the semaphorin family of signaling molecules that acts as a repellent for growing spinal sensory axons. We have constructed a chimeric collapsin-1/alkaline phosphatase probe to visualize putative collapsin-1 receptors in vitro and in situ. As predicted by the activity profile of collapsin-1, the probe binds spinal sensory tracts, ventral spinal roots, and the sympathetic chain but does not bind retinal axons. In addition, we find that the probe binds sensory axons arising from the olfactory epithelium and some, but not all, cranial sensory nerves. As predicted by these binding studies, in vitro assays demonstrate that primary olfactory sensory, trigeminal, and jugular ganglion growth cones collapse in the presence of soluble collapsin-1. Comparing the expression pattern of collapsin-1 with the trajectories of collapsin-1 responsive axons suggests that in both the spinal cord and the olfactory bulb, collapsin-1 prevents premature entry of sensory axons into their target and helps determine the final location of sensory terminations.

Large-scale reorganization at multiple levels of the somatosensory pathway follows therapeutic amputation of the hand in monkeys

Reorganization of somatosensory cortex after peripheral nerve damage typically has been attributed to cortical plasticity. Here we provide evidence that much of the large-scale cortical reorganization that occurs after a major loss of peripheral inputs reflects the sprouting or expansion of afferents from the remaining forelimb into deprived territories of the spinal cord and brainstem. We examined sensory afferent terminations in the spinal cord and brainstem, and determined the somatotopic organization of cortical area 3b in three adult monkeys with previous hand or forearm amputation, as veterinary treatment of forelimb injuries. In each monkey, the distribution of labeled sensory afferent terminations from the remaining parts of the fore-limb was much more extensive than the normal distribution of inputs from the forelimb, and extended into portions of the dorsal horn of the spinal cord and the cuneate nucleus of the brainstem related to the amputated hand. In the same animals, tactile stimulation of the forelimb activated much of the deprived hand representation in area 3b of cortex; the lateral portion of the deprived region in area 3B appeared to be reactivated by inputs from the face. These data provide important new evidence that one of the mechanisms subserving large scale reorganization in cortex is a relay of topographic changes that occur subcortically. Presumably, the expanded primary sensory inputs activate postsynaptic neurons that are normally driven by inputs from the hand so that the neurons now have receptive fields on the forearm. Since the topographic representation of the body is greatly magnified in the relay to cortex, the subcortical changes can result in dramatic cortical map changes.

An electron microscopic description of glutamate‐like immunoreactive axon terminals in the rat principal sensory and spinal trigeminal nuclei

The spinal and principal sensory trigeminal nuclei relay noxious and nonnoxious stimuli from the orofacial region to the thalamus. Physiological studies have implicated glutamate as an important neurotransmitter in this region. Despite its importance as a potential transmitter, few studies have examined the anatomical distribution of glutamate within these nuclei. We therefore chose to use a monoclonal antibody raised against glutamate conjugated to a carrier protein to identify and describe glutamate-like immunoreactive processes at the electron microscopic level. Glutamate-like immunoreactive axon terminals were identified throughout the spinal trigeminal and principal sensory trigeminal nucleus. In subnucleus caudalis glutamate-like immunoreactive terminals occurred frequently in all laminae and were morphologically heterogeneous. In lamina I, glutamate-like immunoreactive terminals were primarily ovoid, contained spherical synaptic vesicles, and participated in synaptic complexes with both dendritic and axonal profiles. In laminae II and III many glutamate-like immunoreactive axon terminals were identified as the central element in synaptic glomeruli. Within discrete patches of lamina II, large numbers of glutamate-like immunoreactive terminals contained dense core vesicles. The majority of glutamate-like immunoreactive terminals in subnucleus interpolaris, subnucleus oralis, and principal sensory trigeminal nucleus were similar in morphology and synaptic interaction to the glutamate-like immunoreactive terminals found in subnucleus caudalis. Glutamate-like immunoreactive terminals that were the central presynaptic element in glomerular complexes were seen in all subnuclei. In sections from subnucleus interpolaris and subnucleus oralis central glutamate-like immunoreactive terminations within glomerular complexes had much smoother profiles, and in subnucleus interpolaris participated primarily in axodendritic synaptic junctions. In the principal sensory trigeminal nucleus central glutamate-like immunoreactive terminations were highly scalloped and participated in numerous axoaxonic synaptic junctions. The above observations are consistent with the hypothesis that glutamate-like immunoreactivity is present in some primary afferent terminations and functions as an important excitatory transmitter involved in the relay of sensory information to the spinal trigeminal and principal sensory trigeminal nucleus.

Spatial relationships between the terminations of somatic sensory motor pathways in the rostral brainstem of cats and monkeys. II. Cerebellar projections compared with those of the ascending somatic sensory pathways in lateral diencephalon.

Previous studies have shown that ascending somatic sensory pathways arising from the dorsal column nuclei, lateral cervical nucleus and spinothalamic tract terminate in parts of the thalamus adjacent to those which receive cerebellar terminations. This termination pattern creates a border between the ventroposterolateral nucleus (VPL) and the ventrolateral nucleus (VL) in the cat and between the caudal and oral parts of VPL (VPLc and VPLo, respectively) in the monkey. Since it is not clear how sharp these borders are, a double orthograde labeling strategy was used in the present study to make direct comparisons of the projections to the thalamus from these sources of input. It was found that there was a change in the sources of afferent input to the different target areas that paralleled changes in cytoarchitecture. Moving caudally to rostrally, VPL in the cat and VPLc in the monkey received projections predominantly from the middle, dorsal (clusters) portion of the dorsal column nuclei. These projections were gradually replaced near the VPL-VL border in the cat and VPLc-VPLo border in the monkey first by input from the lateral cervical nucleus (cat only) and the rostral and ventral portions of the dorsal column nuclei and then by spinothalamic projections. Towards VL in the cat and the rostral parts of VPLo in the monkey (referred to as Vim by Hassler, '59 and Mehler, '71), these projections were in turn replaced by those from the cerebellum. This sequence resulted in a complex pattern (summarized in Fig. 10) where some thalamic territories received input predominantly from one source and others received converging input from several sources. The major region receiving converging ascending somatic sensory and cerebellar terminations was located at the border between VPL and VL in the cat and in the caudal parts of Olszewski's ('52) VPLo in the monkey (that is, between VPLc and Vim). In general, the results in the cat were similar to those in the monkey. One notable difference was that the domain containing terminals from the cerebellum and the rostral-ventral parts of the dorsal column nuclei was located medially between VPLc and Vim in the monkey, whereas it extended across the entire mediolateral border between VPL and VL in the cat. In both species, thalamic neurons received input predominantly from one afferent source and only minor input, if any, from other sources.(ABSTRACT TRUNCATED AT 400 WORDS)

Muscle spindle formation and differentiation in regenerating rat muscle grafts

Muscle spindle development and function are dependent upon sensory innervation. During muscle regeneration, both neural and muscular components of spindles degenerate and it is not known whether reinnervation of a regenerating muscle results in reestablishment of proper neuromuscular relationships within spindles or whether sensory neurons may exert an influence upon differentiation of these spindles. Muscle spindle regeneration was studied in bupivacaine-treated grafts of rat extensor digitorum longus (EDL) muscles. Three types of EDL graft were performed in order to manipulate the extent to which regenerating spindles might be reinnervated: (1) grafts reinnervated following severance of their nerve supply (standard grafts); (2) grafts in which intact nerve sheaths appear to facilitate reinnervation (nerveintact grafts); and (3) grafts in which reinnervation was prevented (nonreinnervated grafts). Complete degeneration of muscle fibers occurred in all grafts prior to regeneration. Initial formation of spindles in regenerating EDL grafts is independent of innervation; intrafusal muscle fibers degenerate and regenerate within spindle capsules that remain intact and viable. The extent of spindle differentiation was evaluated in each type of graft using criteria that included nucleation and ATPase activity, both of which have been shown to be regulated by sensory innervation, as well as the number of muscle fibers/spindle and morphology of spindle capsules. While most spindles contained normal numbers of muscle fibers, most of these fibers were morphologically and histochemically abnormal. Alterations of ATPase activity occurred in all spindles, but were least severe in nerve-intact grafts. While fully differentiated nuclear bag and chain fibers were not observed in regenerated spindles, large, vesicular nuclei, similar to those of normal intrafusal fibers, were present in a small number of spindles in nerve-intact grafts. Sensory nerve terminations were observed only in those spindles that also contained the distinctive nuclei. This study suggests that a specific neurotrophic influence is necessary for regeneration of normal intrafusal muscle fibers and that this influence corresponds to the properly timed sensory neuron-muscle interaction which directs muscle spindle embryogenesis. However, the infrequent occurrence of characteristics unique to intrafusal muscle fibers indicates that reinnervation of regenerating muscle grafts by sensory neurons is inadequate and/or faulty.

Lysophosphatidyl choline facilitates labeling of CNS projections with horseradish peroxidase

Previously, it has been difficult to label sensory terminations in the CNS by backfilling peripheral sensory nerves with horseradish peroxidase (HRP), apparently because the amount of HRP transported along the axons is insufficient. Labeling of central sensory projections in axolotls and frogs can be improved by agents known to disrupt membranes. Of those tested, l-α-lysophosphatidyl choline is the most effective. The addition of this detergent to the HRP solution dramatically increases both the number of axons labeled and the density of label within single axons.

Transganglionic and anterograde transport of horseradish peroxidase across dorsal root ganglia: A tetramethylbenzidine method for tracing central sensory connections of muscles and peripheral nerves

Horseradish peroxidase was applied either to severed sciatic nerves or to individual muscle groups in the lower leg of the rat. This horseradish peroxidase was taken up by sensory nerves and transported across the dorsal root ganglion and then anterogradely as far as central sensory terminals in the spinal cord and medulla. The dorsal root, dorsal column and the tract of Lissauer contained horseradish peroxidase labeled fibers. Following horseradish peroxidase application to the cut sciatic nerve, extraperikaryal reaction-product within the central processes of the sensory neurons was seen in the upper dorsal horn (substantia gelatinosa), lower dorsal horn, intermediate gray, ventral horn and nucleus of Clarke of the ipsilateral spinal cord; in the contralateral dorsal and ventral horns, and in the ipsilateral nucleus gracilis. Following intramuscular injections of horseradish peroxidase, the reaction-product was virtually absent in the upper dorsal horn and was concentrated in the lower dorsal horn, intermediate gray and ventral horn. These experiments show that horseradish peroxidase is transported anterogradely in significant quantities along the intact central processes of the dorsal root ganglion so that sensory terminations belonging to individual peripheral nerves or muscle groups can be traced. The demonstration of this complex transport was made possible with a sensitive histochemical method that used tetramethylbenzidine as the chromogen. Alternate sections processed with a commonly employed diaminobenzidine procedure did not show any of these central sensory connections.

The connections of the sensory organ of Bellonci with the brain in Isopoda (crustacea).

The peduncle linking the organ of Bellonci with the brain was examined in Sphaeroma serratum and Anilocra frontalis. This peduncle, in its extension to the brain, becomes a nerve-like tract with bundles of pedicles originating from the sensory cell bodies located in the organ of Bellonci. It ends at the level of the medulla interna in an alveolar region resulting from the swelling of the sensory pedicle terminations. At this level three types of connections have been observed. The first is characterized by afferent synapses to the brain with, in the sensory pedicle endings, structures similar to the presynaptic ribbons noted by some authors in photoreceptors of arthropods. The two other types include nerve fibres originating from the brain, one with small electron lucent vesicles, a second displaying larger vesicles with a core of medium density. These fibres form efferent synapses to the organ of Bellonci. The sensory differentiation of the organ of Bellonci in Isopoda is confirmed but its true role is not specified.

Two unusual satellite cell-intrafusal muscle fiber relationships.

We studied the location and ultrastructure features of rat teres minor intrafusal muscle fiber satellite cells. They were abundant in myotube and polar regions, particularly near sensory nerve terminals and terminations of the spindle capsule and intrafusal muscle fibers. One satellite cell was wedged between two “paired” nuclear bag fibers in the myotube region. No basement membrane surrounded this cell. A polar satellite cell was encased by the basement membrane for only part its length. This cell contained numerous myofilaments. It terminated in the intercellular space surrounded by its own basement membrane adjacent to the host nuclear bag fiber. Recent satellite cell investigations are summarized and compared with the results of this study. We conclude there may be more than one cell type in the satellite cell position and intrafusal and extrafusal satellite cells may function in different capacities.

Effect of tri-O-cresyl phosphate (TOCP) poisoning on sensory nerve terminations of slow loris (Nycticebus coucang coucang).

Sensory nerve terminations in the oral and digital tissues of slow loris (Nycticebus coucang coucang) were studied after topical or systemic administration of TOCP. Histochemical studies revealed a reduction of AChE and complete absence of ChE in sensory nerve terminations. In electron microscopy the light cells of taste buds showed vacuolization, degenerating mitochondria, distended endoplasmic reticulum, vesicle formation and “cytosegregosomes” while dark cells also has unusual shaped dense core granular vesicles (1,200–2,500 A diameter). The axons were “ballooned” with fragmenting mitochondria, some agranular vesicles and disorientated neurotubules lying in a dispersed, lightly granular axoplasm. Moreover, the Nauta-Gygax method (1954) revealed degenerative changes in the digital sensory end-organs as well as in the distal portion of the sensory nerve fibres. The significance of these findings is discussed.