Immunohistochemical localization of neurocalcin in human sensory neurons and mechanoreceptors

Single Administration of Melatonin Modulates the Nitroxidergic System at the Peripheral Level and Reduces Thermal Nociceptive Hypersensitivity in Neuropathic Rats

Neuropathic pain is a severe condition with unsatisfactory treatments. Melatonin, an indolamine, seems to be a promising molecule suitable for this purpose due to its well-known anti-inflammatory, analgesic, and antioxidant effects, as well as its modulation of the nitroxidergic system. Nevertheless, the data on its mechanism of action and potentialities are currently insufficient in this pathology, especially at the peripheral level. Thus, this work evaluated the effect of a single administration of melatonin in an established mononeuropathy pain model that monitors the behaviour and the changes in the nitroxidergic system in dorsal root ganglia and skin, which are affected by nervous impairment. Experiments were carried out on Sprague Dawley rats subdivided into the sham operated (control) and the chronic constriction injured animals, a model of peripheral neuropathic pain on sciatic nerve. Single administrations of melatonin (5–10 mg/kg) or vehicle were injected intraperitoneally on the 14th day after surgery, when the mononeuropathy was established. The animals were behaviourally tested for thermal hyperalgesia. The dorsal root ganglia and the plantar skin of the hind-paws were removed and processed for the immunohistochemical detection of neuronal and inducible nitric oxide synthases. The behavioural results showed an increase of withdrawal latency during the plantar test as early as 30 min after melatonin administration. The immunohistochemical results indicated a modulation of the nitroxidergic system both at dorsal root ganglia and skin level, permitting speculate on a possible mechanism of action. We showed that melatonin may be a possible therapeutic strategy in neuropathic pain.

Cellular localization of aquaporin-1 in the human and mouse trigeminal systems

Previous studies reported that a subpopulation of mouse and rat trigeminal neurons express water channel aquaporin-1 (AQP1). In this study we make a comparative investigation of AQP1 localization in the human and mouse trigeminal systems. Immunohistochemistry and immunofluorescence results showed that AQP1 was localized to the cytoplasm and cell membrane of some medium and small-sized trigeminal neurons. Additionally, AQP1 was found in numerous peripheral trigeminal axons of humans and mice. In the central trigeminal root and brain stem, AQP1 was specifically expressed in astrocytes of humans, but was restricted to nerve fibers within the central trigeminal root and spinal trigeminal tract and nucleus in mice. Furthermore, AQP1 positive nerve fibers were present in the mucosal and submucosal layers of human and mouse oral tissues, but not in the muscular and subcutaneous layers. Fluorogold retrograde tracing demonstrated that AQP1 positive trigeminal neurons innervate the mucosa but not skin of cheek. These results reveal there are similarities and differences in the cellular localization of AQP1 between the human and mouse trigeminal systems. Selective expression of AQP1 in the trigeminal neurons innervating the oral mucosa indicates an involvement of AQP1 in oral sensory transduction.

Nitroxidergic system in human trigeminal ganglia neurons: a quantitative evaluation

The trigeminal ganglia are involved in transmission of orofacial sensitivity. The free radical gas nitric oxide (NO) has recently been found to function as a messenger molecule in both central and peripheral trigeminal primary afferent neurons. NO is produced within neurons mainly by two enzymes: a constitutive (neuronal) form of NO synthase (nNOS) or an inducible form of NOS (iNOS). The aim of the study was to evaluate the distribution of trigeminal neurons according to size (small, medium and large neurons) and to correlate the percentage of NOS-immunopositive neurons with regard to neuronal size. The results showed a significant relationship between the percentage of nNOS-immunopositive neurons and the size of neurons. Evaluation of the percentage of nNOS-immunopositive neurons showed that they constitute about 50% of the total number of neurons and that they are represented mainly as large-sized neurons. The iNOS immunolabelling was very faint in all neuronal types. Since the nitroxidergic system is well represented in human trigeminal ganglia, this study indicates that it could play a relevant role in trigeminal neurotransmission.

The Meissner and Pacinian sensory corpuscles revisited new data from the last decade

This article reviews the biochemical, physiological, and experimental data cumulated during the last decade on the Meissner and Pacinian corpuscles. It includes information about (i) the localization of molecules recently detected in sensory corpuscles; (ii) the unsolved problem of the accessory fibers in sensory corpuscles and the occurrence of myelin within them; (iii) the development of sensory corpuscles, especially their neuronal and growth factor dependency; (iv) the composition and functional significance of the extracellular matrix as an essential part of the mechanisms involved in the genesis of the stimuli generated in sensory corpuscles; (v) the molecular basis of mechanotransduction; (vi) a miscellaneous section containing sparse new data on the protein composition of sensory corpuscles, as well as in the proteins involved in live-death cell decisions; (vii) the changes in sensory corpuscles as a consequence of aging, the central, or peripheral nervous system injury; and finally, (viii) the special interest of Meissner corpuscles and Pacinian corpuscles for pathologists for the diagnosis of some peripheral neuropathies and neurodegenerative diseases.

Characterization of sensory deficits in TrkB knockout mice

The sensory deficit in TrkB deficient mice was evaluated by counting the neuronal loss in lumbar dorsal root ganglia (DRG), the absence of sensory receptors (cutaneous--associated to the hairy and glabrous skin - muscular and articular), and the percentage and size of the neurocalcin-positive DRG neurons (a calcium-binding protein which labels proprioceptive and mechanoceptive neurons). Mice lacking TrkB lost 32% of neurons, corresponding to the intermediate-sized and neurocalcin-positive ones. This neuronal lost was accomplished by the absence of Meissner corpuscles, and reduction of hair follicle-associated sensory nerve endings and Merkel cells. The mutation was without effect on Pacinian corpuscles, Golgi's organs and muscle spindles. Present results further characterize the sensory deficit of the TrkB-/- mice demonstrating that the intermediate-sized neurons in lumbar DRG, as well as the cutaneous rapidly and slowly adapting sensory receptors connected to them, are under the control of TrkB for survival and differentiation. This study might serve as a baseline for future studies in experimentally induced neuropathies affecting TrkB positive DRG neurons and their peripheral targets, and to use TrkB ligands in the treatment of neuropathies in which cutaneous mechanoreceptors are primarily involved.

Neurocalcin-immunoreactive neurons in the petrosal ganglion innervate the taste bud

The distribution and origin of neurocalcin-immunoreactive (NC-ir) nerve fibers in the taste bud and carotid body were examined by an immunofluorescence method. In the circumvallate papilla of the tongue, NC-ir nerve fibers made subepithelial nerve plexuses and occasionally penetrated the taste bud. However, the carotid body was devoid of ir nerve fibers. In the petrosal ganglion, 32% of neurons were immunoreactive for NC. Such neurons were mostly medium-sized to large, and scattered throughout the ganglion. In the superior cervical and intralingual ganglia, numerous ir varicose fibers surrounded postsynaptic neurons. However, NC-ir could not be detected in cell bodies of these neurons. The retrograde tracing method indicated that NC-ir petrosal neurons innervated taste buds in the circumvallate papilla. NC-ir neurons may have a gustatory function in the petrosal ganglion.

Horse lumbrical muscle: possible structural and functional reorganization in regressive muscle

An anatomical study of horse lumbrical muscle (Lm) was carried out by light and electron microscopy in combination with immunochemical and cytochemical methods. Paraffin sections were subjected to haematoxylin and eosin (H & E) and Masson's trichrome staining for morphometric analysis. Paraffin sections were also used for immunostaining by anti-PGP 9.5 for reaction with nerve-protein associated-structures, anti-heat-shock protein 70 (hsp 70) for detection of gene expression changes, anti-fast myosin for the determination of muscle fibre types, and for detection of apoptotic gene expression of muscle fibres by the TUNEL method. The distribution of muscle fibre types on frozen sections was also examined by assaying ATPase (pH 4.2). We found that the proximal end of the tendon of the unipennate-shaped Lm binds to the deep digital flexor tendon, and the distal end of the Lm tendon connects to the medial surface of the palmar annular ligament. The Lm was not always present, but when found it varied in length greatly, up to 8 cm (muscle part alone), and weighed less than 1 g. The Lm was white, pale, or reddish in colour depending on the ratio of muscle fibre and connective tissue contents. The semi-tendinized regressive Lm was composed of rich vasculature, peripheral nerves, and nerve-like organs similar to the neuromuscular spindle (NMS). The extrafusal muscle fibres (e-lm) that surround the NMS were replaced with a thick outer capsule of connective tissues (CT) in the Lm nerve-like organ, which we named the neurotendinous capsule (NTC) organ. NTC organs exist alone or as multiple structures (up to eight) surrounded by a common outer capsule at the outermost CT ring. The NTC possesses several intrafusal muscle fibres (ifm) just as the NMS does. That the ifm was associated with nerve endings was confirmed by anti-PGP 9.5 and electron microscopic observation. Some muscle fibres in ifm and e-lm reacted with anti-fast twitch myosin and with anti-hsp 70. The e-lm exhibited at least two fibre types, determined by ATPase (pH 4.2) assay. The ifm exhibited mainly type I (slow twitch) fibres. No apoptotic gene expression was detected in either ifm or e-lm, suggesting the Lm is a vital organ. The degenerating fibres observed in ifm and e-lm indicate that the turnover rate of cytoplasmic components is accelerated. We attribute this phenomenon to the necessity for adaptation to new environmental demands. The surprising finding of tubular aggregates (TAs) in ifm of the NTC organ suggests that the Lm is continuously adapting. Some results related to variation in diameter of the collagen fibrils, isolation of the NTC organ and the myofibrillar protein constituents are also discussed. In conclusion, the so-called regressive Lm has rich vasculature, many peripheral nerves, and newly described NTC organs. The induction of heat-shock protein, lack of apoptotic gene expression in ifm and e-lm fibres, and TA formation in ifm suggest that horse Lm responds to environmental stress through reorganization and/or remodelling of cell constituents. We hypothesize that the horse Lm has lost its original role as a contractile element and changed to another function, likely as a vital nerve organ.

Neurocalcin-alpha immunoreactivity in the enteric nervous system of young and aged rats

The distribution of the calcium binding protein neurocalcin a has been examined in the enteric nervous system of young adult (3 months) and aged (24+ months) male rats by immunofluorescence. Neurocalcin-immunoreactive (NC-ir) neurons were observed in the submucous and myenteric plexuses throughout the gastrointestinal tract from the oesophagus to the distal large intestine. NC-ir nerve terminals were also seen on NC-ir and NC-negative neurons. Semiquantitative estimates revealed fewer NC-ir neurons in the submucous plexus than in the myenteric plexus. The greatest occurrence of NC-ir neurons was in the small and large intestine. NC-ir axons were seen in the mucosa and also in between the ganglia of the myenteric plexus. In the aged rats, there were no discernible changes in the numbers of NC-ir neurons in th e oesophagus and stomach, with an increase in the pylorus and slight decreases in the small and large intestines. No decrease in NC-ir was observed in the distal large intestine. NC-ir neurons never contained lipofuscin age pigment and many enteric neuro ns devoid of NC-ir contained age pigment. Like other previously investigated calcium-binding proteins in enteric neurons, the distribution of NC shows much variability from one part of the intestine to another. The observed slight decreases in the number of NC-ir enteric neurons in aged rats may compromise the regulation of calcium in these neurons.

Molecular cloning, mapping and characterization of the human neurocalcin delta gene (NCALD)

We identified a new human gene that encodes a cognate of the bovine neurocalcin delta from a human fetal brain cDNA library; hence we named it human neurocalcin delta (NCALD) gene. The deduced polypeptide product of the cDNA is 22 kDa in size, and its amino acid sequence is 100% and 99% identical to that of the bovine and chicken neurocalcin, respectively. Northern blots showed that the NCALD gene is more abundantly expressed in brain, testis, ovary and small intestine. Tissue in situ hybridization confirmed the existence of the NCALD mRNA in the adult human testis. Radiation hybrid panel mapping localized the gene to chromosome 8 between molecular markers D8S270 and D8S257.

Decreased neurocalcin immunoreactivity in sympathetic and parasympathetic neurons of the major pelvic ganglion in aged rats

In the rat the majority of sympathetic and parasympathetic postganglionic neurons that innervate the pelvic viscera are located together in the major pelvic ganglia. We have ascertained that it is only the sympathetic population of this ganglion that exhibits age-associated attrition. Recent immunohistochemical investigations of the distribution of calcium binding proteins in this ganglion in young adult and aged rats have demonstrated that calbindin-D28k is only present in the sympathetic neurons and that the number of calbindin-immunoreactive sympathetic neurons of the aged ganglion was dramatically reduced. In the present study we have investigated the distribution of neurocalcin (NC) alpha isoform in the major pelvic ganglion. In young adults 98.7% of sympathetic neurons (identified by anti-tyrosine hydroxylase immunostaining) and 98% of parasympathetic neurons (identified by anti-nitric oxide synthase immunostaining) contained NC immunoreactivity and these figures are reduced to 68 and 45.5% in the aged group. Thus, unlike calbindin-D28k, NC is not confined to the sympathetic neuron population in the major pelvic ganglion and decreases significantly in old age in both neuronal populations. The likely effects are to impair intracellular calcium-dependent signalling in neurons of the major pelvic ganglion, possibly compounding the effects of the previously reported decrease in calbindin-D28k in the sympathetic population.

Neurocalcin-immunoreactive neurons in the mammalian dorsal root ganglia, including humans

Neurocalcin (NC) is a recently characterized EF-hand calcium-binding protein present in a discrete population of sensory neurons and their peripheral mechanoreceptors, but its presence in peripheral nervous system neurons other than in the rat is still unknown. The present study was designed to investigate the occurrence of NC in the dorsal root ganglia (DRG) of several mammalian species (horse, buffalo, cow, sheep, pig, dog, and rat), including humans. DRG were fixed, embedded in paraffin, and processed for immunohistochemistry using a polyclonal antibody against NC. The size of the immunoreactive neurons was measured. In all species examined, NC immunoreactivity (IR) was restricted to neurons but the percentage, as well as the size of the immunoreactive neurons, varied among different species. As a rule, small neurons (diameter <20 microm) lack NC IR. In some species (pig, dog, buffalo, cow), only the largest neurons showed IR, whereas in others (sheep, horse, rat, and humans) they covered the entire range of neuron sizes. The pattern of immunostaining was cytoplasmic, although in some species (cow and buffalo), it formed a peripheral "ring." The present results demonstrate that mammalian DRG contain a subpopulation of NC-positive neurons, which varies from one species to another. Based on the neuron size, the possible function of the NC-containing neurons is discussed.