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PubMedDate not supplied

Mechanosensory perception: are there contributions from bone-associated receptors?

1. The identity of the receptors and afferent nerve fibres that mediate the sense of touch varies somewhat with body location. Those that have been most intensively characterized are associated with the distal glabrous skin of the limbs and, in primates, mediate the sense of touch in the fingertips and palms. In this glabrous skin region, there appear to be three or four principal classes of tactile sensory nerves that fall into two broad groups. One group, the so-called slowly adapting (SA) receptors and afferent fibres, is responsive to static mechanical displacement of skin tissues and is made up of two classes, the type I (SAI) fibres that innervate Merkel receptors and the type II (SAII) fibres that innervate Ruffini endings. The second broad group displays a pure dynamic sensitivity to tactile stimuli and also falls into two principal classes, the rapidly adapting (RA) tactile fibres that are associated with Meissner corpuscle receptors and the Pacinian corpuscle (PC)-associated class of tactile afferent fibres. 2. In other regions of the skin, such as the hairy skin of the arms, legs and trunk, there are similar functional classes of tactile sensory nerves, although the receptor endings differ somewhat from those of the glabrous skin. 3. Receptors in close association with the long bones of the limbs include groups of Pacinian corpuscles distributed along the interosseous membranes. These are highly sensitive to dynamic forms of mechanical stimuli, in particular vibrotactile disturbances. However, despite their close association with bone, these receptors probably cannot be legitimately considered 'osseoreceptors'. 4. Both the periosteum and the bone marrow are richly supplied by nerve fibres. However, much evidence indicates that these are largely or entirely in the fine-diameter category of nerve fibres, whose roles may be confined to either nociception or to the efferent autonomic regulation of bone-associated blood vessels. 5. In conclusion, it remains uncertain whether any aspects of our innocuous touch or kinaesthetic senses, in either the limbs or in orofacial regions, can be ascribed to 'osseoreceptors' located in the periosteum or within the bone marrow itself.

Animals↗
PubMed1969

The nature and location of certain phasic mechanoreceptors in the cat's foot.

1. The locations of the receptor endings of twenty-two phasic, primary afferent units which could be excited by small (less than 40 mum) point displacements of cats' large foot pads have been determined by dissection.2. Eleven of these units had endings located within or immediately below the skin on the plantar surface of the pad; eight had endings located deep within the pad and three had endings on the digits.3. All the deep and digital endings were of the PC type of Jänig, Schmidt & Zimmermann (1968) whilst five of the superficial endings were definitely of the RA type of Jänig et al. (1968), and another five could have been. One superficial ending had properties intermediate between those of RA and PC receptors.4. It was shown by dissection that the endings of four of the PC type units were Pacinian corpuscles and such corpuscles were seen within 1 mm of the apparent location of six other PC receptors. Pacinian corpuscles were found close to only two of the eleven superficial receptor locations.5. It is therefore concluded that of the two functionally distinct types of phasic receptors studied, the PC receptors are Pacinian corpuscles located deep in the pad or on the digits, whilst the RA receptors are located within or immediately below the skin and are not Pacinian corpuscles.

Animals↗
PubMed1998

Immunohistochemical characteristics of human paraganglion cells and sensory corpuscles associated with the urinary bladder. A developmental study in the male fetus, neonate and infant.

Triple label immunohistochemistry was used to study the coexistence of the catecholamine-synthesising enzymes dopamine beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) and several neuropeptides including neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), somatostatin (SOM) and galanin (GAL) as well as nitric oxide synthase (NOS) in developing pelvic paraganglion cells in a series of human male fetal, neonatal and infant specimens ranging in age from 13 wk of gestation to 3 y postnatal. 13-20 wk old fetal specimens possessed large clusters of paraganglion cells lying lateral to the urinary bladder and prostate gland which were intensely DBH-immunoreactive (-IR) but lacked TH, NOS and the neuropeptides investigated. With increasing fetal age small clusters of paraganglion cells were observed in the muscle coat of the urinary bladder. At 23 wk of gestation occasional paraganglion cells were NOS or NPY-IR while at 26 wk of gestation the majority of paraganglion cells were TH-IR and a few were SOM or GAL-IR. Some postnatal paraganglia within the bladder musculature contained cells which were all VIP, SP or CGRP-IR while others displayed coexistence of NOS and NPY, SP and CGRP, or NPY and VIP. The presence of NOS in certain paraganglion cells indicates their capacity to generate nitric oxide (NO). These results show that human paraganglion cells develop different phenotypes possibly dependent upon their location within the bladder wall. A delicate plexus of branching varicose nerves was observed in the fetal paraganglia which increased in density with increasing gestational age. The majority of these nerves were VIP-IR while others were CGRP, SP, NPY, NOS or GAL-IR. The presence of nerve terminals adjacent to the paraganglion cells implies a neural influence on the functional activity of the paraganglia. Some paraganglia in the late fetal and early postnatal specimens contained Timofeew's sensory corpuscles, resembling pacinian corpuscles in their morphology. The central nerve fibre of these corpuscles displayed immunoreactivity for SP, CGRP and NOS, the latter indicating a possible role for NO in afferent transmission from the urinary bladder. In addition, a few corpuscles were penetrated by a noradrenergic nerve fibre immunoreactive for NPY and TH, which may have a modulatory role on the sensory receptor.

Calcitonin Gene-Related Peptide↗
PubMed1977

Sensory nerve endings in the penis in green monkey (Cercopithecus aethiops sabaeus).

The authors examined the sensory innervation of the skin in the penis in green monkey in four adult individuals both in the light and in the elctron microscope. They found 3 kings of nerve endings. The free nerve endings were the most frequently occurring kind of nerve endings in the superficial layers of the corium--altogether 6,444 in number. The second kind of sensory nerve endings is represented by the glomerular endings out of which 96 per cent were found in the papillae. The typical Meissner's endings were observed in the light microscopy only rarely. Deeper in the corium the authors also found single simple sensory corpuscles and Pacinian corpuscles. Studying the ultrastructure the authors found in the papillae of the corium 4 types of glomerular endings: quite simple glomerular endings with irregularly arranged Schwann cells, larger and more complicated glomerular endings having a thicker capsule, endings with lamellar system around the terminals and typical Meissner's endings. In the epidermis the authors observed naked axons which passed in the spaces among the epidermal cells. They contained an accumulation of mitochondria. In the basal cell layer of the epidermis there was a small amount of Langerhans cells.

Animals↗
PubMed1982

[Analysis of the modulating effect of catecholamines on electrogenesis in an isolated mechanoreceptor].

Superfusion of the isolated Pacinian corpuscles from cat mesenterium with solutions containing dibutyril-cAMP or theophylline caused an increase in spike activity and a decrease in receptor potential amplitude and firing potential threshold. An opposite effect was observed after catecholamine application. It was suggested that the effect of catecholamines on the Pacinian corpuscles is accompanied by a decrease in the cAMP level in a sensory nerve terminal. Norepinephrine decreased the adenylate cyclase activity and activated Na+, K+-ATPase in homogenates of Pacinian corpuscles. The effect of norepinephrine on Na+, K+-ATPase could be eliminated by phentolamine and was not sensitive to propranolol. A possible participation of alpha-adrenoreceptors in modulating catecholamine effect on electrical activity of the Pacinian corpuscles is discussed.

Adenosine Triphosphate↗
PubMed1997

Effect of spinal cord and peripheral nerve injury on human cutaneous sensory corpuscles. An immunohistochemical study.

This study was aimed at analyzing the changes in cutaneous sensory corpuscles from the territory of lesioned nerves and clinically denervated skin of patients with spinal cord injury using immunohistochemical methods. The morphological and biochemical characteristics of the Schwann-related cells of the mature sensory corpuscles (lamellar cells of Meissner corpuscles and inner-core of Pacinian corpuscles) depend upon the axon. To clarify whether this dependence requires structural and/or functional integrity of sensory axons we analyzed immunohistochemically some axonal, Schwann cell and perineurial cell antigens in cutaneous sensory corpuscles from i) the underlesional levels of patients with spinal cord injury affecting dorsal and lateral funiculi; ii) peripheral nerve entrapment, iii) sectioned and grafted nerves. Skin biopsy samples from the hand or feet were processed for peroxidase-antiperoxidase immunohistochemistry using monoclonal antibodies directed against neurofilament proteins (to label the axons), S-100 protein (to label Schwann-related cells), epithelial membrane antigen (to label the perineurial derivatives), vimentin (to label both Schwann cell and perineurial derivatives). Meissner and Pacinian corpuscles of subjects suffering from spinal cord lesions showed an immunohistochemical profile close to normality, although in many of them S-100 protein was unevenly distributed or absent. Sensory corpuscles of the cutaneous territory of entrapped nerves were in most cases similar to those of normally innervated skin. The most striking finding in these subjects was the hyperinnervation of blood vessels and sweat glands. Finally, nerve section and subsequent unsuccessful graft repair resulted in absence of immunostaining for all the assessed antigens in sensory corpuscles. The present results suggest that structural, but not functional, integrity of the axon is essential in maintaining some immunohistochemical characteristics of the human cutaneous sensory corpuscles. Morphological findings are correlated and discussed in relation to the clinical evaluation of the sensitivity.

Adult↗
PubMed1982

The ultrastructure of axon processes in sensory corpuscles.

The authors studied the ultrastructure of axon processes in simple sensory corpuscles, Herbst and Pacinian corpuscles. They give a description of their shape, topographical localization and relation to organelles. They focused their attention to the incidence of various kinds of vesicles in the processes and at their bases, and the incidence and localization of of mitochondria. The most frequently occurring vesicles are those of medium electron density (clear vesicles), in small numbers there are also dense core vesicles and coated vesicles. The incidence of vesicles is predominantly polarized, i.e. they are situated at the bases of axon processes, opposite the so-called clefts of the inner core. In sporadic cases reach into the processes besides clear vesicles also mitochondria. Direct connection between axon processes and inner core lamellae was not observed. The authors are considering the possible importance of these processes in the transmission of stimuli to the axon. They are of the opinion that further studies are necessary to specify the morpho-physiological relations inside sensory corpuscles.

Animals↗
PubMed1994

Differential expression of beta 1, beta 3, and beta 4 integrin subunits in nonneoplastic neural cells of the peripheral and autonomic nervous system and in tumors derived from these cells.

BACKGROUND: Extracellular matrix proteins and their receptors take part in physiologic neural development and organization and also in abnormal neoplastic growth and spread. There is increasing evidence for the implication of integrins in these processes. EXPERIMENTAL DESIGN: Human tissues containing nonneoplastic neural cells of the peripheral and autonomic nervous system and a comprehensive series of neural tumors were examined for the in situ expression of beta 1, beta 3, and beta 4 integrins. Serial frozen sections of each tissue sample were immunostained using an indirect streptavidin/biotin-peroxidase method and monoclonal antibodies against beta 1, alpha 1 to alpha 6, beta 3, alpha v, and beta 4 subunits. RESULTS: Both small- and large-diameter nerve fibers of normal peripheral nerve trunks were consistently beta 1+, alpha 6+, and beta 4+ in the absence of alpha 3, alpha 4, alpha 5, and beta 3. Small-diameter nerve fibers further expressed alpha 1, alpha 2, and alpha v. Meissner's corpuscles and inner cores of Pacinian corpuscles shared the integrin repertoire of small-diameter nerve fibers with additional expression of alpha 3; outer cores of Pacinian corpuscles were beta 1+, alpha 3+, alpha 6+, and beta 4+. Regenerating nerve fibers paralleled the integrin profile of normal peripheral nerves. By contrast, malignant schwannomas showed considerable changes in integrin expression. These alterations consisted mainly in a neoexpression of alpha 3, alpha 4, and alpha 5 and in an abnormal loss of alpha 6 and beta 4. Expression of alpha 1, alpha 2, and alpha v was variable; absence of beta 3 was generally conserved. In ganglion cells, integrin expression was restricted to beta 1 and alpha 3 subunits, and chromaffine cells of the adrenal medulla even lacked any detectable beta 1, beta 3, and beta 4 integrin subunits. (Ganglio)-neuroblastomas, however, were beta 1+, alpha 1+, and alpha 3+, whereas primitive peripheral neuroectodermal tumors were beta 1+ and alpha 5+. CONCLUSIONS: Nonneoplastic human neural cells exhibit a complex and, at the same time, differential pattern of beta 1, beta 3, and beta 4 integrin subunit expression. Malignant transformation leads to considerable changes in this integrin profile. The observation of neoplasia-associated abnormalities underlines the important role of integrins in the orderly development and maintenance of human neural tissue. Some aspects of the emerging integrin subunit patterns are useful for the differential diagnosis of neural soft-tissue tumors.

Adrenal Glands↗
PubMed1984

Immunohistological demonstration of S-100 protein in the cutaneous nervous system.

S-100 protein, isolated from mammalian brain, has widely been used for immunohistochemical marker of the glia cells and the cells derived from the neural crest. In the present study, we made anti S-100 protein antibody and studied the immunoreactive distribution of S-100 protein in the cutaneous nervous system. Albino rabbits were immunized with S-100 protein and complete Freund adjuvant, and antiserum was purified by ion-exchange chromatography. Formalin-fixed normal human skin and sciatic nerve of rat were examined by the PAP method. S-100 protein was detected in Schwann cells of sciatic nerve of rat and cutaneous nerve bundles of human skin specimens. Meissner corpuscles and inner core cells of Pacinian corpuscles of human skin were S-100 protein positive. These findings suggest that the staining of S-100 protein with PAP method is a simple and reliable method to demonstrate the cutaneous nervous system. Also, lamellar cells of Meissner corpuscles and inner core cells of Pacinian corpuscles are indicated to be Schwann cell origin.

Animals↗
PubMed2002

Synaptic transmission between single tactile and kinaesthetic sensory nerve fibers and their central target neurones.

Selective activation of single tactile or kinaesthetic afferent nerve fibers in conscious human subjects by means of the intraneural microstimulation procedure reveals quite marked differences among the different classes in their capacity for eliciting perceptual responses. This work, conducted largely by Swedish researchers, suggests that there may be differential transmission security for different fiber classes across synaptic linkages in the central tactile and kinaesthetic sensory pathways. In order to test this hypothesis we have developed an experimental paradigm in the anaesthetized cat, based upon paired, simultaneous recording from an individual afferent fiber in an intact peripheral nerve fascicle, and from the central target neurone of that afferent fiber within the dorsal column nuclei (DCN). Our results demonstrate, for all tactile and kinaesthetic fiber classes examined, that the minimum sensory input, a single impulse in one sensory fiber, can generate spike output from DCN target neurones. This remarkable security of transmission has been demonstrated for single Pacinian corpuscle (PC) fibers (associated with Pacinian Corpuscle receptors); single SAI and SAII fibers (the slowly adapting Type I and II tactile fibers associated, respectively, with Merkel and Ruffini receptor endings); the Hair Follicle Afferent fibers (HFA fibers); and kinaesthetic afferent fibers of both joint and muscle origin. The results demonstrate that the differential capacities of various tactile and kinaesthetic fiber classes to generate perceptual responses when activated singly in microneurography experiments do not appear to be explicable in terms of systematic differences in DCN transmission characteristics.

Animals↗
PubMedDate not supplied

Physiological characteristics of low-threshold mechanoreceptors in joints, muscle and skin in human subjects.

1. The development of microneurography, in which an insulated tungsten microelectrode is inserted into an accessible peripheral or cranial nerve in awake human subjects, has allowed detailed analyses of the signalling capacities of single mechanoreceptive afferents from the skin, muscles and joints. For example, we know much about how the two classes of rapidly adapting (Meissner and Pacinian) and two classes of slowly adapting (Merkel and Ruffini) cutaneous mechanoreceptors encode forces applied normal or tangential to the skin of the hand and the similarities and differences in glabrous versus non-glabrous skin (and receptors associated with hairs). We also know about stretch- and force-sensitive endings in muscle (the muscle spindle and Golgi tendon organ, respectively) and how they behave during passive or active movements or during isometric contractions. In addition, we have characterized the firing properties of mechanoreceptors in the joint capsules of the fingers. However, we know little about sensory nerves in the periosteum, other than that nociceptors and Pacinian corpuscles exist. 2. In addition to studies on the physiology of sensory endings in human subjects, microstimulation through the recording microelectrode has revealed how the brain deals with the sensory information conveyed by a single afferent. From this work, we know that there is specificity in the sensory channels: electrical stimulation of a single Meissner or Pacinian corpuscle generates frequency dependent illusions of 'flutter' or 'vibration', whereas microstimulation of a single Merkel afferent can produce a percept of 'pressure' and stimulation of a single joint afferent can evoke a sensation of 'joint rotation'. Interestingly, the input from a single Ruffini ending in the skin cannot be perceived and the same is true of muscle spindle afferents. So, where does this leave us with osseoperception from the mouth? Given that the periodontal receptors in the vicinity have been lost, which mechanoreceptive endings could encode forces applied to a bone-implanted prosthesis? 3. Meissner and Merkel endings have very small receptive fields and respond only to local forces. Pacinian corpuscles have an exquisite sensitivity to brisk mechanical events and could respond to such stimuli transmitted through the bone to a remote receptor, but would not be able to encode sustained forces. Ruffini endings also respond to forces applied remote to the receptive field and, unlike the Pacinian corpuscles, respond in a sustained fashion, but would their signals be perceived? Like muscle spindles, it is possible that the coactivation of many Ruffini endings could provide meaningful information. Finally, as we have seen, the input from a single joint receptor can be perceived, but they mostly respond at the limits of joint rotation, so it is unlikely that any associated with the temporomandibular joint could contribute to osseoperception.

Animals↗
PubMed1983

Segmental actions of afferents of the interosseous nerve in the cat.

Electrical stimulation of the interosseous nerve evokes oligosynaptic inhibition of extensor motoneurones and excitation of flexor motoneurones. Lowest-threshold, shortest-latency post-synaptic potentials evoked at group I strength are attributed to the action of group Ib afferents. Post-synaptic potentials evoked at slightly higher stimulus strengths (within the higher group I and the group II range) and at longer latency are attributed to the action of afferents of Pacinian corpuscles. Facilitation of post-synaptic potentials evoked from afferents in the interosseous nerve by group I muscle afferents and by joint afferents is taken to indicate convergence of these afferents onto common interneurones in reflex pathways to motoneurones. Evidence is presented that afferents of Pacinian corpuscles project to the interneurones mediating group I (non-reciprocal) reflex actions to motoneurones. Unitary monosynaptic excitatory post-synaptic potentials (e.p.s.p.s) evoked from the interosseous nerve are taken to indicate that only a very small number of muscle spindle Ia afferents course through the interosseous nerve. Dorsal root potentials evoked by low-strength electrical stimulation of the interosseous nerve are largely attributable to the action of afferents of Pacinian corpuscles.

Action Potentials↗
PubMed1998

Morphological study of mechanoreceptors on the coracoacromial ligament.

We performed gold chloride staining of coracoacromial ligaments removed at operation, observed the peripheral nerve endings in the ligament, and studied their distribution and changes with aging in order to clarify the proprioception of the shoulder joint. The coracoacromial ligament was found to contain four types of typical nerve endings: Pacinian corpuscles, Ruffini receptors, Golgi tendon organ-like receptors, and free nerve endings. In addition, non-typical Pacinian corpuscles and Ruffini receptors with non-typical morphology were present. There were also unclassifiable nerve endings with a morphology which did not fit any of the above categories. These typical, non-typical, and unclassifiable nerve endings were all widely distributed on the surface of the subacromial side at the insertion into the acromion and around the coracoid process in the ligament. Free nerve endings were found sporadically on the surface of the subacromial bursal side in the ligament. The resected coracoacromial ligaments (23 specimens) were divided into two groups based on the disorder that required surgery: a fracture group without subacromial impingement (5 specimens) and a group with subacromial impingement (18 specimens). Age-related changes in the number of nerve endings were compared in each group. The total number of nerve endings decreased with age in both groups. The number of Pacinian corpuscles, Ruffini receptors, Golgi tendon organ-like receptors, and free nerve endings of typical morphology tended to decrease with age. The data from the fracture and subacromial impingement groups were not analyzed statistically because of the difference in the number of specimens in each group. However, the total number of nerve endings was lower in the subacromial impingement group than in the fracture group at all ages. The typical nerve endings of the coracoacromial ligament in both groups tended to decrease in the elderly, suggesting that the proprioception of the shoulder joint may become impaired with aging.

Acromioclavicular Joint↗
PubMed2004

[Branched form of the encapsulated dermal receptors in rats].

Using electron microscope the receptors found in the zone of highest receptor sensitivity in the skin fold at the base of IV finger of rat hind limb were studied. These receptors are represented by complex incapsulated corpuscles consisting of a group of small endings similar to Pacinian corpuscles, which are densely packed and surrounded by a common connective tissue capsule. Each single primary receptor is provided with an unmyelinated receptor terminal, analogue of internal bulb, and a multilayered external bulb. Primary receptor differs from Vater-Pacinian corpuscle by a significantly smaller size, form of sensitive terminal in cross-section, small number of layers forming internal and external bulbs. Complex corpuscle is the derivative of n. tibialis myelinated sensory fiber. The later is divided after the loss of myelin forming a platform of division with several (up to 5) short sprouts and separate incapsulated receptors at their ends. The complex corpuscles described apparently are dermal mechanoreceptors.

Animals↗
PubMed1977

Human tactile detection thresholds: modification by inputs from specific tactile receptor classes.

1. Human detection thresholds for a vibratory stimulus applied to the volar surface of the index finger were examined under conditions where afferents from specific tactile receptor classes were simultaneously activated from the thenar eminence. The experiments were designed to test whether stimuli which have been shown previously to induce afferent inhibition of ;tactile' neurones in the cuneate nucleus of the cat could modify human subjective performance in a tactile detection task. Conditioning stimuli to the thenar eminence were usually of three forms; steady indentation to engage slowly adapting tactile receptors; 300 Hz vibration to engage Pacinian corpuscles; and 30 Hz vibration to engage the intradermal, rapidly adapting tactile receptors which are thought to be Meissner's corpuscles.2. In ten subjects the mean detection threshold for a 30 Hz test stimulus in the absence of conditioning stimulation was 8.6 +/- 1.0 mum (S.E.). Detection thresholds were increased substantially in the presence of a 300 Hz, 100 mum conditioning stimulus (mean increase 11.1 +/- 2.0 mum), whereas minor or insignificant effects were seen with conditioning stimuli consisting of (a) 30 Hz, 100 mum (mean increase 1.4 +/- 0.8 mum), (b) steady indentation, 1.5 mm in amplitude (mean increase 1.3 +/- 0.7 mum) or (c) 300 Hz, 100 mum to the contralateral thenar eminence (mean increase 0.4 +/- 0.5 mum).3. The 300 Hz conditioning stimulus to the ipsilateral thenar eminence caused a marked increase in detection thresholds at all test stimulus frequencies over the range 10-450 Hz. The effects of the conditioning stimulation therefore operated on inputs from Pacinian corpuscles, which are responsible for vibration detection at 80-450 Hz, and on inputs from the intradermal, rapidly adapting receptors which are responsible for vibration detection at 10-80 Hz.4. The band width of conditioning vibratory frequencies which was effective at amplitudes of 100 mum in bringing about increases in detection threshold extended from 50-80 Hz to 300 Hz, the maximum tested.5. Whereas amplitudes of 1-2 mum produced clear increases in detection thresholds with conditioning stimuli of 300 Hz, amplitudes of > 200 mum were needed at 30 Hz.6. The observed elevations in detection threshold are consistent with an afferent-induced inhibitory action exerted at synaptic relays of the sensory pathway by tactile inputs arising exclusively or predominantly from Pacinian corpuscles.

Adult↗
PubMed1997

Glial growth factor rescues Schwann cells of mechanoreceptors from denervation-induced apoptosis.

Golgi tendon organs and Pacinian corpuscles are peripheral mechanoreceptors that disappear after denervation during a critical period in early postnatal development. Even if regeneration is allowed to occur, Golgi tendon organs do not reform, and the reformation of Pacinian corpuscles is greatly impaired. The sensory nerve terminals of both types of mechanoreceptors are closely associated with Schwann cells. Here we investigate the changes in the Schwann cells found in Golgi tendon organs and Pacinian corpuscles after nerve resection in the early neonatal period. We report that denervation induces the apoptotic death of these Schwann cells and that this apoptosis can be prevented by administration of a soluble form of neuregulin, glial growth factor 2. Schwann cells associated with these mechanoreceptors are immunoreactive for the neuregulin receptors erbB2, erbB3, and erbB4, and the sensory nerve terminals are immunoreactive for neuregulin. Our results suggest that Schwann cells in developing sensory end organs are trophically dependent on sensory axon terminals and that an axon-derived neuregulin mediates this trophic interaction. The denervation-induced death of mechanoreceptor Schwann cells is correlated with deficiencies in the re-establishment of these sensory end organs by regenerating axons.

Animals↗
PubMed1985

Distribution of sensory receptors in the flexor carpi radialis muscle of the cat.

The structures and distribution of encapsulated muscle receptors were examined in serial transverse sections of flexor carpi radialis in the adult cat. Four types of receptors (muscle spindles, Golgi tendon organs, paciniform, and Pacinian corpuscles) were identified. Their structures resembled those encountered in other limb muscles. Pacinian corpuscles were rare and occurred only in the external fascial coat of the muscle near its origin. The other three receptor types were distributed in an uneven but consistent pattern throughout the muscle. As noted previously (Gonyea and Ericson, '77), spindles were largely confined to a deep muscle region comprising less than 20% of the muscle volume, located directly between the long tendon of origin and the tendon of insertion. This region contains the largest proportion of type SO muscle fibers (Gonyea and Ericson, '77). Tendon organs and paciniform corpuscles were concentrated along the tendons that lined the spindle-rich muscle region. This region appeared to be composed of extrafusal fibers that were shorter and of more oblique pinnation than those in other regions. The localization of muscle receptors to the "oxidative" core of the muscle in its direct line of pull may have functional implications for afferent input to the spinal cord which are discussed. In addition, the possibility is raised that there are more paciniform corpuscles in flexor carpi radialis (and possibly other muscles) than previously thought.

Animals↗
PubMed2000

Immunohistochemical localization of neurocalcin in human sensory neurons and mechanoreceptors.

The localization of neurocalcin in the developing and adult human peripheral nervous system (dorsal root and sympathetic ganglia (DRG, SG), and enteric nervous system (ENS)) was investigated using immunohistochemistry. A subpopulation of large-sized neurons in DRG of 9 and 12 weeks old embryos showed immunoreactivity (IR), whereas the sympathetic ganglia or enteric neurons did not. In adults, neurocalcin IR was restricted to a subpopulation of large (13%) and intermediate (15%) sized neurons in DRG. The protein was also found in muscular (67%) and cutaneous (12%) nerve fibers, as well as in the axons supplying muscular (muscle spindles, Golgi's tendon organs, and perimysial Pacinian corpuscles) and cutaneous (Meissner's but not Pacinian corpuscles) mechanoreceptors, as well as motor end-plates. Present results demonstrate that neurocalcin in both developing and adult humans can be used as a specific marker for a subpopulation of sensory neurons coupled to proprioception and touch, and for axons of motoneurons forming motor end-plates.

Adult↗