Ontogeny of peptide- and amine-containing neurones in motor, sensory, and autonomic regions of rat and human spinal cord, dorsal root ganglia, and rat skin

The Distribution of Innervation and Immune Cell Infiltration Is Different in Genital and Extragenital Variants of Lichen Sclerosus

Lichen sclerosus (LS) is a progressive skin disease that is characterized by chronic inflammation of either genital or extragenital skin, and it disproportionately affects women. We analyzed the distribution of nerve fibers, vanilloid receptors, cell proliferation, mast cells and macrophages in genital and extragenital LS samples, as well as in healthy skin, by using immunohistochemistry. The total amount of intraepidermal nerve fibers was lower in LS samples compared to healthy controls, while the total amount of subepidermal nerve fibers and calcitonin gene-related peptide (CGRP) positive fibers was higher in genital LS samples compared to both extragenital LS and healthy controls. Cell proliferation, macrophage and mast cell density were increased in LS samples compared to healthy controls. Genital LS had a higher macrophage density compared to the extragenital variant. Mast cell distribution significantly differed between genital and extragenital LS samples, even though their total mast cell densities were similar. These findings could explain the differences between pruritic symptoms of genital and extragenital LS and provide targets for the research of novel therapeutic strategies for LS management.

A neuropeptide code for itch

Itch is one of the most primal sensations, being both ubiquitous and important for the well-being of animals. For more than a century, a desire to understand how itch is encoded by the nervous system has prompted the advancement of many theories. Within the past 15 years, our understanding of the molecular and neural mechanisms of itch has undergone a major transformation, and this remarkable progress continues today without any sign of abating. Here I describe accumulating evidence that indicates that itch is distinguished from pain through the actions of itch-specific neuropeptides that relay itch information to the spinal cord. According to this model, classical neurotransmitters transmit, inhibit and modulate itch information in a context-, space- and time-dependent manner but do not encode itch specificity. Gastrin-releasing peptide (GRP) is proposed to be a key itch-specific neuropeptide, with spinal neurons expressing GRP receptor (GRPR) functioning as a key part of a convergent circuit for the conveyance of peripheral itch information to the brain.

CLARITY with neuronal tracing and immunofluorescence to study the somatosensory system in rats

BACKGROUND

The CLARITY technique enables researchers to visualize different neuronal connections along the nervous system including the somatosensory system.

NEW METHOD

The present work describes the antero-lateral and dorsal column pathways until the thalamic and cortical stations, as well as descending oxytocinergic and vasopressinergic innervations by means of combined CLARITY, neuronal tracing, and immunofluorescence techniques. We used male Sprague-Dawley rats of 13, 30, and 60 days.

RESULTS

The main results are as follows: A) CLARITY is a reliable technique that can be combined with fluorescent neuronal tracers and immunofluorescence techniques without major procedure modifications; B) at spinal level, some primary afferent fibers were labeled by CGRP, as well as the presence of neuronal populations that simultaneously project to the gracile and ventral posterolateral thalamic nuclei; C) corticothalamic connections were visible when retrograde tracers were injected at thalamic level; D) oxytocin receptors were expressed in the spinal dorsal horn by GABAergic-positive neurons, reinforcing previous outcomes about the possible mechanism for oxytocin blocking the primary afferent sensory input.

COMPARISON WITH EXISTING METHODS AND CONCLUSIONS

The CLARITY technique lets us observe in a transparent way the entire processed tissue compared with classical histological methods. CLARITY is a potentially useful tool to describe neuroanatomical structures and their neurochemical stratus.

Lumbar spinal cord neurons putatively involved in ejaculation are sexually dimorphic in early postnatal mice

A crucial role in ejaculation is thought to be played by a population of lumbar spino-thalamic neurons (LSt), which express galanin and other neuropeptides. In rats, these neurons are activated with ejaculation and their lesion selectively abolishes ejaculation but not other mating behaviors. Consistently with their role, in adult rats and humans, LSt neurons are sexually dimorphic, being more numerous in males. Here we examined whether sexual dimorphism arises early in development, using a transgenic mouse line in which the expression of fluorescent protein is driven by the galanin promoter. We focused on postnatal day 4, shortly after a transient perinatal androgen surge in males that could play an organizational role in LSt development. We found a population of brightly fluorescent neurons organized in bilateral columns dorsolateral to the central canal in segments L1-L5, the expected location of the LSt group. Their number was close to that of adult preparations and significantly greater in male than in female siblings (+19%; CI_95% : +13% to +27%; p < .01). This was not due to a generalized higher galanin expression in the male since fluorescent L4 DRG neurons, innervating the hindlimbs and lower back, were not significantly dimorphic (-4%; CI_95% : -10% to +8%; p = .92). Unexpectedly, we found in cervical segments a population of fluorescent neurons having a location relative to the central canal similar to the LSt. Thus, the LSt group is sexually dimorphic soon after birth. However, it is possible that only a subset of its neurons participate in the control of ejaculation.

CGRP in Animal Models of Migraine

With the approval of calcitonin gene-related peptide (CGRP) and CGRP receptor monoclonal antibodies by the Federal Drug Administration, a new era in the treatment of migraine patients is beginning. However, there are still many unknowns in terms of CGRP mechanisms of action that need to be elucidated to allow new advances in migraine therapies. CGRP has been studied both clinically and preclinically since its discovery. Here we review some of the preclinical data regarding CGRP in animal models of migraine.

Human Dorsal Root Ganglia

Sensory neurons with cell bodies situated in dorsal root ganglia convey information from external or internal sites of the body such as actual or potential harm, temperature or muscle length to the central nervous system. In recent years, large investigative efforts have worked toward an understanding of different types of DRG neurons at transcriptional, translational, and functional levels. These studies most commonly rely on data obtained from laboratory animals. Human DRG, however, have received far less investigative focus over the last 30 years. Nevertheless, knowledge about human sensory neurons is critical for a translational research approach and future therapeutic development. This review aims to summarize both historical and emerging information about the size and location of human DRG, and highlight advances in the understanding of the neurochemical characteristics of human DRG neurons, in particular nociceptive neurons.

Perivascular Adipose Tissue: the Sixth Man of the Cardiovascular System

Perivascular adipose tissue (PVAT) refers to the local aggregate of adipose tissue surrounding the vascular tree, exhibiting phenotypes from white to brown and beige adipocytes. Although PVAT has long been regarded as simply a structural unit providing mechanical support to vasculature, it is now gaining reputation as an integral endocrine/paracrine component, in addition to the well-established modulator endothelium, in regulating vascular tone. Since the discovery of anti-contractile effect of PVAT in 1991, the use of multiple rodent models of reduced amounts of PVAT has revealed its regulatory role in vascular remodeling and cardiovascular implications, including atherosclerosis. PVAT does not only release PVAT-derived relaxing factors (PVRFs) to activate multiple subsets of endothelial and vascular smooth muscle potassium channels and anti-inflammatory signals in the vasculature, but it does also provide an interface for neuron-adipocyte interactions in the vascular wall to regulate arterial vascular tone. In this review, we outline our current understanding towards PVAT and attempt to provide hints about future studies that can sharpen the therapeutic potential of PVAT against cardiovascular diseases and their complications.

Time course and expression pattern of the neuronal markers in the developing human spinal cord

The aim of this study was to examine the spatio-temporal appearance of different neuronal cell subtypes by analyzing expression patterns of several neuronal markers (calretinin, neurofilament 200 (NF200), vanilloid receptor 1(VR1) and calcitonin gene-related peptide (CGRP)) of the embryonic human spinal cord (SC). Developing human SCs from 11 human conceptuses beetwen 5-10 developmental weeks (DW) were examined by light and electron microscopy and immunofluorescence. Light and electron microscopy revealed different embryonic stages of recognizable structure of the SC. NF200, CGRP and VR1 positive cells were observed in SCs during 5th-6th DW. NF200 was predominantly expressed in the ventral part, indicating presence of motoneurons. As development advanced, NF200 was mainly expressed in the marginal zone. Expression of CGRP was intense during all of the investigated periods, predominantly during the 5th-6th DW pointing to neural sensory differentiation, as opposed to the last DW when reduced expression of CGRP in the marginal layer indicated the terminations of the sensory afferents. Expression of VR1 was highest in the intermediate zone, at the beginning and at the end of the investigated periods, pointing to VR1 spatial pattern in the visceral afferents in the grey matter, while the first signs of calretinin were found in the 9th-10th DW ventrally. Delineating the relationships between factors involved in processes of neuronal differentiation as well as spatial and temporal arrangement of SC interrelated neurons can provide a useful information about normal SC development as well as the insight in possible causes of anomalies and disorders during embryonic life.

Oxidative Stress as a Physiological Pain Response in Full-Term Newborns

This research paper aims to investigate if oxidative stress biomarkers increase after a painful procedure in term newborns and if nonpharmacological approaches, or sex, influence pain degree, and the subsequent OS. 83 healthy term newborns were enrolled to receive 10% oral glucose or sensorial saturation (SS) for analgesia during heel prick (HP). The ABC scale was used to score the pain. Advanced oxidation protein products (AOPP) and total hydroperoxides (TH) as biomarkers of OS were measured at the beginning (early-sample) and at the end (late-sample) of HP. The early-sample/late-sample ratio for AOPP and TH was used to evaluate the increase in OS biomarkers after HP. Higher levels of both AOPP and TH ratio were observed in high degree pain (4–6) compared with low degree pain score (0–3) (AOPP: p = 0.049; TH: p = 0.001). Newborns receiving SS showed a significantly lower pain score (p = 0.000) and AOPP ratio levels (p = 0.021) than those without. Males showed higher TH levels at the end of HP (p = 0.005) compared to females. The current study demonstrates that a relationship between pain degree and OS exists in healthy full-term newborns. The amount of OS is gender related, being higher in males. SS reduces pain score together with pain-related OS in the newborns.

Accelerated onset of the vesicovesical reflex in postnatal NGF-OE mice and the role of neuropeptides

The mechanisms underlying the postnatal maturation of micturition from a somatovesical to a vesicovesical reflex are not known but may involve neuropeptides in the lower urinary tract. A transgenic mouse model with chronic urothelial overexpression (OE) of NGF exhibited increased voiding frequency, increased number of non-voiding contractions, altered morphology and hyperinnervation of the urinary bladder by peptidergic (e.g., Sub P and CGRP) nerve fibers in the adult. In early postnatal and adult NGF-OE mice we have now examined: (1) micturition onset using filter paper void assays and open-outlet, continuous fill, conscious cystometry; (2) innervation and neurochemical coding of the suburothelial plexus of the urinary bladder using immunohistochemistry and semi-quantitative image analyses; (3) neuropeptide protein and transcript expression in urinary bladder of postnatal and adult NGF-OE mice using Q-PCR and ELISAs and (4) the effects of intravesical instillation of a neurokinin (NK)-1 receptor antagonist on bladder function in postnatal and adult NGF-OE mice using conscious cystometry. Postnatal NGF-OE mice exhibit age-dependent (R²=0.996-0.998; p≤0.01) increases in Sub and CGRP expression in the urothelium and significantly (p≤0.01) increased peptidergic hyperinnervation of the suburothelial nerve plexus. By as early as P7, NGF-OE mice exhibit a vesicovesical reflex in response to intravesical instillation of saline whereas littermate WT mice require perigenital stimulation to elicit a micturition reflex until P13 when vesicovesical reflexes are first observed. Intravesical instillation of a NK-1 receptor antagonist, netupitant (0.1μg/ml), significantly (p≤0.01) increased void volume and the interval between micturition events with no effects on bladder pressure (baseline, threshold, peak) in postnatal NGF-OE mice; effects on WT mice were few. NGF-induced pleiotropic effects on neuropeptide (e.g., Sub P) expression in the urinary bladder contribute to the maturation of the micturition reflex and are excitatory to the micturition reflex in postnatal NGF-OE mice. These studies provide insight into the mechanisms that contribute to the postnatal development of the micturition reflex.

Developmental localization of calcitonin gene-related peptide in dorsal sensory axons and ventral motor neurons of mouse cervical spinal cord

Calcitonin gene-related peptide (CGRP) is a 37-amino-acid neuropeptide, synthesized by alternative splicing of calcitonin gene mRNA. CGRP is characteristically distributed in the nervous system, and its function varies depending on where it is expressed. To reveal developmental formation of the CGRP network and its function in neuronal maturation, we examined the immunohistochemical localization of CGRP in the developing mouse cervical spinal cord and dorsal root ganglion. CGRP immunolabeling (IL) was first detected in motor neurons on E13, and in ascending axons of the posterior funiculus and DRG neurons on E14. CGRP-positive sensory axon fibers entered Laminae I and II on E16, and Laminae I through IV on E18. The intensity of the CGRP-IL gradually increased in both ventral and dorsal horns during embryonic development, but markedly decreased in the ventral horn after birth. These results suggest that CGRP is expressed several days after neuronal settling and entry of sensory fibers, and that the CGRP network is formed in chronological and sequential order. Furthermore, because CGRP is markedly expressed in motor neurons when axons are vastly extending and innervating targets, CGRP may also be involved in axonal elongation and synapse formation during normal development.

Neonatal pain: What's age got to do with it?

Background:

The neurobiology of neonatal pain processing, especially in preterm infants, differs significantly from older infants, children, adolescence, and adults. Research suggests that strong painful procedures or repeated mild procedures may permanently modify individual pain processing. Acute injuries at critical developmental periods are risk factors for persistent altered neurodevelopment. The purpose of this narrative review is to present the seminal and current literature describing the unique physiological aspects of neonatal pain processing.

Methods:

Articles describing the structures and physiological processes that influence neonatal pain were identified from electronic databases Medline, PubMed, and CINAHL.

Results:

The representation of neonatal pain physiology is described in three processes: Local peripheral nervous system processes, referred to as transduction; spinal cord processing, referred to as transmission and modulation; and supraspinal processing and integration or perception of pain. The consequences of undermanaged pain in preterm infants and neonates are discussed.

Conclusion:

Although the process and pain responses in neonates bear some similarity to processes and pain responses in older infants, children, adolescence, and adults; there are some pain processes and responses that are unique to neonates rendering them at risk for inadequate pain treatment. Moreover, exposure to repeated painful stimuli contributes to adverse long-term physiologic and behavioral sequelae. With the emergence of studies showing that painful experiences are capable of rewiring the adult brain, it is imperative that we treat neonatal pain effectively.

Somatostatin and its 2A receptor in dorsal root ganglia and dorsal horn of mouse and human: expression, trafficking and possible role in pain

Background

Somatostatin (SST) and some of its receptor subtypes have been implicated in pain signaling at the spinal level. In this study we have investigated the role of SST and its sst2A receptor (sst2A) in dorsal root ganglia (DRGs) and spinal cord.

Results

SST and sst2A protein and sst2 transcript were found in both mouse and human DRGs, sst2A-immunoreactive (IR) cell bodies and processes in lamina II in mouse and human spinal dorsal horn, and sst2A-IR nerve terminals in mouse skin. The receptor protein was associated with the cell membrane. Following peripheral nerve injury sst2A-like immunoreactivity (LI) was decreased, and SST-LI increased in DRGs. sst2A-LI accumulated on the proximal and, more strongly, on the distal side of a sciatic nerve ligation. Fluorescence-labeled SST administered to a hind paw was internalized and retrogradely transported, indicating that a SST-sst2A complex may represent a retrograde signal. Internalization of sst2A was seen in DRG neurons after systemic treatment with the sst2 agonist octreotide (Oct), and in dorsal horn and DRG neurons after intrathecal administration. Some DRG neurons co-expressed sst2A and the neuropeptide Y Y1 receptor on the cell membrane, and systemic Oct caused co-internalization, hypothetically a sign of receptor heterodimerization. Oct treatment attenuated the reduction of pain threshold in a neuropathic pain model, in parallel suppressing the activation of p38 MAPK in the DRGs

Conclusions

The findings highlight a significant and complex role of the SST system in pain signaling. The fact that the sst2A system is found also in human DRGs and spinal cord, suggests that sst2A may represent a potential pharmacologic target for treatment of neuropathic pain.

Galanin gene expression and effects of its knock-down on the development of the nervous system in larval zebrafish

Despite the known importance of galanin in the nervous system of vertebrates, the galanin gene structure and expression and the consequences of galanin deficiency in developing zebrafish are unknown. We cloned the galanin gene and analyzed its expression by using in situ hybridization, PCR, and immunocytochemistry throughout the early development of zebrafish until the end of the first week of life. The single zebrafish galanin gene encoded for a single amidated galanin peptide and a galanin message-associated peptide. Two forms resulting from alternative processing were identified. Galanin mRNA was maternally expressed and found in developing fish throughout early development. In situ hybridization showed the first positive neurons in three groups in the brain at 28 hours postfertilization. At 2 days postfertilization, three prosencephalic neuron groups were seen in the preoptic area and in rostral and caudal periventricular hypothalamus. In addition, two other groups of weakly stained neurons were visible, one in the midbrain and another in the hindbrain. Translation inhibition of galanin mRNA with morpholino oligonucleotides caused complete disappearance of galanin immunoreactivity in the brain until 7 dpf and did not induce known cascades of nonspecific pathways or morphological abnormalities. A minor disturbance of sensory ganglia was found. Galanin knockdown did not alter the expression of tyrosine hydroxylases 1 and 2, choline acetyltransferase, histidine decarboxylase, or orexin mRNA. The results suggest that galanin does not regulate the development of these key markers of specific neurons, although galanin-expressing fibers were in a close spatial proximity to several neurons of these neuronal populations.

[Pain in the fetus: neurobiological, psychophysiological and behavioral aspects.]

Until a short time ago, the view prevailed worldwide that children were less sensitive to pain than adults, and such operations as circumcision were performed in babies without adequate anesthesia or analgesia. This view is now considered a misconception, as psychophysiological and behavioral studies show that even neonates have a well-functioning nociceptive system. Nociception generally refers to the neural and sensory aspects of pain, which do not necessarily include conscious experience. There is no discontinuity in the development of the nervous system during birth, and therefore it can be concluded that the fetus is also responsive to noxious stimuli. The question arises as to the stage of ontogeny of the human at which nociceptive behavior begins. Literature on the fetal nervous system reveals that the first signs of somatosensory system function occur at week 7 of gestation and at week 22 the synaptic connection from the nervous periphery to the somatosensory cortex is becoming established. During this period, motor behavior matures, from stereotyped reflexes to spontaneously generated complex motor patterns reminiscent of the repertory of voluntary movement. From week 22 onward the electroencephalogram (EEG) shows increasingly more varied patterns, and sleep-wake states can be discerned after week 30 of gestation. Somatosensory evoked cortial potentials have been recorded from gestational week 28 onward. Substance P, a neuropeptide associated with pain in the adult nervous system, is present in the fetal spinal cord as early as week 12 of gestation, while the antinociceptive opioid peptide enkephalin does not appear until week 24. From week 15 onward, opioid peptides such as beta-endorphin appear in the pituitary; their release becomes sensitive to environmental stimuli from about week 20 onward, which can be considered the onset of pituitary stress responses. In particular, parturition and abortion induced the release of opioid peptides. Studies of conditioned behavior show that the fetus has the ability to learn. It has been hypothesized that the fetus and neonate possess a procedural memory, which is not transferred to the language-based memory of later phases of life. Learning and memory are the most essential elements for the construct of "consciousness." Therefore, a primitive type or level of consciousness might exist in the fetus. Thus, a considerable range of sensorimotor function, including memory, develops during fetal life. Anatomical, physiological and behavioral data suggest that the nociceptive system is included in this development. Although we cannot be sure at present whether the fetus consciously experiences pain, beyond the protective nociceptive behavioral responses, anesthesia should be used for invasive procedures to protect the fetus and its nervous systems.

The mechanism of calcitonin gene-related peptide-containing nerve innervation

Calcitonin gene-related peptide (CGRP) is a major neurotransmitter and CGRP-containing primary sensory neurons play an important role in nociception and potent vasodilation. CGRP-containing nerves in mesenteric arteries are decreased in pathological animal models (hypertension, diabetes, and atherosclerosis). In apolipoprotein E&ndash;knockout mice, which have atherosclerosis and peripheral sensory nerve defects, nerve growth factor (NGF)-mediated CGRP nerve facilitation was down-regulated, which may have been caused by the impairment of the Akt&ndash;NO&ndash;cGMP pathway. In addition, NGF-mediated CGRP neurite outgrowth was decreased in fructose-induced insulin-resistant rats. We recently discovered that renin&ndash;angiotensin inhibitors improved CGRP innervation in spontaneously hypertensive rats, indicating that rescuing CGRP nerve innervation might improve pathophysiological conditions. To find a novel reagent that facilitates CGRP nerves, a new model, phenol-injured perivascular nerve model rats, was established. Adrenomedullin, hepatocyte growth factor, and angiotensin II type 2 receptor activation induced CGRP nerve distribution in phenol-injured rats. Furthermore, in insulin-resistant model rats, the down-regulation of CGRP nerves was likely due to the depression of phosphoinositide 3-kinase (PI3K)-dependent Akt activation. Administration of candesartan improves CGRPergic function via the PI3K&ndash;Akt pathway in insulin-resistant rats. Thus, clarification of the mechanisms of CGRP nerve defects may constitute future therapeutic targets.

Transforming growth factor-β in normal nociceptive processing and pathological pain models

The transforming growth factor-β (TGF-β) superfamily is a multifunctional, contextually acting family of cytokines that participate in the regulation of development, disease and tissue repair in the nervous system. The TGF-β family is composed of several members, including TGF-βs, bone morphogenetic proteins (BMPs) and activins. In this review, we discuss recent findings that suggest TGF-β function as important pleiotropic modulators of nociceptive processing both physiologically and under pathological painful conditions. The strategy of increasing TGF-β signaling by deleting "BMP and activin membrane-bound inhibitor" (BAMBI), a TGF-β pseudoreceptor, has demonstrated the inhibitory role of TGF-β signaling pathways in normal nociception and in inflammatory and neuropathic pain models. In particular, strong evidence suggests that TGF-β1 is a relevant mediator of nociception and has protective effects against the development of chronic neuropathic pain by inhibiting the neuroimmune responses of neurons and glia and promoting the expression of endogenous opioids within the spinal cord. In the peripheral nervous system, activins and BMPs function as target-derived differentiation factors that determine and maintain the phenotypic identity and circuit assembly of peptidergic nociceptors. In this context, activin is involved in the complex events of neuroinflammation that modulate the expression of pain during wound healing. These findings have provided new insights into the physiopathology of nociception. Moreover, specific members of the TGF-β family and their signaling effectors and modulator molecules may be promising molecular targets for novel therapeutic agents for pain management.

The analgesic properties of intraoral sucrose: an integrative review

The treatment of pain is an essential component of the clinical and ethical care of infants. Despite evidence-based practice consensus statements recommending that infants receive analgesia during minor painful procedures, numerous studies have shown that procedural pain remains poorly managed in this population. Oral sucrose administration has been associated with calming effects and reductions in observed pain behaviors with preterm and term infants aged up to 1 year. The objective of this integrative review is to synthesize findings from published randomized controlled trials evaluating the efficacy and safety of oral sucrose as a preprocedural intervention for mild to moderate procedural pain in infants. Overall, studies indicate that oral sucrose is an effective, safe, convenient, and immediate-acting analgesic for reducing crying time and significantly decreases biobehavioral pain response following painful procedures with infants.

Bradykinin and prostaglandin E₁ regulate calcitonin gene-related peptide expression in cultured rat sensory neurons

Primary cultures of adult rat dorsal root ganglia (DRG) sensory neurons were used to determine whether bradykinin and prostaglandins E₁ (PGE₁), E₂ (PGE₂) or I₂ (PGI₂) stimulate long-term calcitonin gene-related peptide (CGRP) mRNA accumulation and peptide release. Treatment (24 h) of neurons with either bradykinin or PGE₁, significantly increased CGRP mRNA content and iCGRP release. However, PGE₂ or PGI₂ was without effect. Exposure of the cultured neurons to increasing concentrations of bradykinin or PGE₁ demonstrated that the stimulation of CGRP expression was concentration-dependent, while time-course studies showed that maximal levels of CGRP mRNA accumulation and peptide release were maintained for at least 48 h. Treatment of the neuronal cultures with a bradykinin B₂ receptor antagonist significantly inhibited the bradykinin-induced increase in CGRP expression and release. In addition, preincubation of neuronal cultures with the cyclooxygenase inhibitor indomethacin did not alter the PGE₁-mediated stimulation of CGRP but blocked completely the bradykinin-induced increase in CGRP production. Therefore, these data indicate that bradykinin and PGE₁ can regulate the synthesis and release of CGRP in DRG neurons and that the stimulatory effects of bradykinin on CGRP are mediated by a cyclooxygenase product(s). Thus, these findings suggest a direct relationship between chronic alterations in bradykinin/prostaglandin production that may arise from pathophysiological causes and long-term changes in CGRP expression.

Differentiation of spinal motor neurons from pluripotent human stem cells

We have devised a reproducible protocol by which human embryonic stem cells (hESCs) or inducible pluripotent stem cells (iPSCs) are efficiently differentiated to functional spinal motor neurons. This protocol comprises four major steps. Pluripotent stem cells are induced to form neuroepithelial (NE) cells that form neural tube-like rosettes in the absence of morphogens in the first 2 weeks. The NE cells are then specified to OLIG2-expressing motoneuron progenitors in the presence of retinoic acid (RA) and sonic hedgehog (SHH) or purmorphamine in the next 2 weeks. These progenitor cells further generate post-mitotic, HB9-expressing motoneurons at the 5th week and mature to functional motor neurons thereafter. It typically takes 5 weeks to generate the post-mitotic motoneurons and 8-10 weeks for the production of functional mature motoneurons. In comparison with other methods, our protocol does not use feeder cells, has a minimum dependence on proteins (purmorphamine replacing SHH), has controllable adherent selection and is adaptable for scalable suspension culture.

Role of neurotrophin signalling in the differentiation of neurons from dorsal root ganglia and sympathetic ganglia

Manipulation of neurotrophin (NT) signalling by administration or depletion of NTs, by transgenic overexpression or by deletion of genes coding for NTs and their receptors has demonstrated the importance of NT signalling for the survival and differentiation of neurons in sympathetic and dorsal root ganglia (DRG). Combination with mutation of the proapoptotic Bax gene allows the separation of survival and differentiation effects. These studies together with cell culture analysis suggest that NT signalling directly regulates the differentiation of neuron subpopulations and their integration into neural networks. The high-affinity NT receptors trkA, trkB and trkC are restricted to subpopulations of mature neurons, whereas their expression at early developmental stages largely overlaps. trkC is expressed throughout sympathetic ganglia and DRG early after ganglion formation but becomes restricted to small neuron subpopulations during embryogenesis when trkA is turned on. The temporal relationship between trkA and trkC expression is conserved between sympathetic ganglia and DRG. In DRG, NGF signalling is required not only for survival, but also for the differentiation of nociceptors. Expression of neuropeptides calcitonin gene-related peptide and substance P, which specify peptidergic nociceptors, depends on nerve growth factor (NGF) signalling. ret expression indicative of non-peptidergic nociceptors is also promoted by the NGF-signalling pathway. Regulation of TRP channels by NGF signalling might specify the temperature sensitivity of afferent neurons embryonically. The manipulation of NGF levels "tunes" heat sensitivity in nociceptors at postnatal and adult stages. Brain-derived neurotrophic factor signalling is required for subpopulations of DRG neurons that are not fully characterized; it affects mechanical sensitivity in slowly adapting, low-threshold mechanoreceptors and might involve the regulation of DEG/ENaC ion channels. NT3 signalling is required for the generation and survival of various DRG neuron classes, in particular proprioceptors. Its importance for peripheral projections and central connectivity of proprioceptors demonstrates the significance of NT signalling for integrating responsive neurons in neural networks. The molecular targets of NT3 signalling in proprioceptor differentiation remain to be characterized. In sympathetic ganglia, NGF signalling regulates dendritic development and axonal projections. Its role in the specification of other neuronal properties is less well analysed. In vitro analysis suggests the involvement of NT signalling in the choice between the noradrenergic and cholinergic transmitter phenotype, in the expression of various classes of ion channels and for target connectivity. In vivo analysis is required to show the degree to which NT signalling regulates these sympathetic neuron properties in developing embryos and postnatally.

Age-related changes in dorsal root ganglia, circulating and vascular calcitonin gene-related peptide (CGRP) concentrations in female rats: effect of female sex steroid hormones

The aim of the present study is to investigate whether immunoreactive (I) calcitonin gene-related peptide (CGRP) content is decreased in plasma and mesenteric arteries (resistance arteries) in middle-aged rats and if so, whether sex steroid hormones enhance I-CGRP in middle-aged female rats. We also examined whether vascular CGRP receptor components, calcitonin receptor like receptor (CRLR) and receptor activity modifying protein 1 (RAMP1) are elevated by sex steroid hormones treatment in middle-aged female rats. Young adult (3 months old) and middle-aged (10-12 months old) ovariectomized rats were treated subcutaneously with estradiol-17beta (E2; 2 mg), progesterone (P4; 5 mg), E2+P4 (2 mg+20 mg) or placebo (control). Radioimmunoassay and Western blot analysis were performed to measure I-CGRP content and CGRP receptor components in dorsal root ganglia (DRG), in resistance arteries and in plasma. Immunofluorescent staining methods were employed to determine cellular localization of CRLR, RAMP1 in resistance arteries. Our data demonstrated that I-CGRP content was significantly (p<0.05) lower in the plasma and resistance arteries of middle-aged female rats compared to young controls. Both RAMP1 and CRLR were concentrated in vascular endothelium and the underlying smooth muscle cells. RAMP1 but not CRLR appeared to be decreased in middle-aged rat vasculature. Chronic perfusion of sex steroid hormones to ovariectomized rats: 1 significantly (p<0.05) elevated I-CGRP in the DRG and in the plasma, and (2) significantly elevated RAMP1 (p<0.05) but did not alter CRLR in resistance arteries. These data suggest that female sex steroid treatment enhances I-CGRP and its receptors, and thus regulate the blood pressure in aged female rats.

Expression and changes of neuropeptide Y in the development of mouse stomach

AIM: To observe expression, distribution and development of neuropeptide Y in stomach of mouse embryo and to investigate relationship between the histological changes, functions and neuropeptide Y.

METHODS: HE staining and immunohistochemistry SABC method were used to study the expression of mouse stomach neuropeptide Y from embryonic day 13 (E13D) to day 21 (E21D).

RESULTS: Neuropeptide Y was positively expressed in embryonic muscle and epithelial mucosa with the successive growth in the mucosal plexus, muscular mucosa, submucosa, submucosal plexus in the fetal rat stomach at different development stages. Immune-response was increasingly strong with its peak value in E18D. There was a significant increase in the total number density of NPY in the stomach wall in E15D and significant differences were observed between E15D and E14D (2.26 ± 4.19 vs 1.05 ± 3.91, P < 0.05). The total area density was significantly increased in E18D, and significant difference was noted between E14-16D and E19D-21D (9.00 ± 3.41 vs 1.12 ± 1.10, 1.88 ± 4.75, 3.77 ± 5.09, 3.39 ± 3.11, 3.36 ± 4.11, 3.43 ± 3.16, P < 0.01); positive expression mucosa density was significantly higher in E18D than in the other groups (7.35 ± 5.01vs 2. 45 ± 2.79, 3. 41 ± 3.25, 5.89 ± 7.43, 3.55 ± 3.78, 4.33 ± 6.52, 3.21 ± 6.25, 2.77 ± 6.13, P < 0.05 or 0.01).

CONCLUSION: E14-E18D is a critical period in development of mice stomach. Neuropeptide Y is closely related to development of stomach.

Development, plasticity and modulation of visceral afferents

Visceral pain is the most common reason for doctor visits in the US. Like somatic pain, virtually all visceral pain sensations begin with the activation of primary sensory neurons innervating the viscera and/or the blood vessels associated with these structures. Visceral afferents also play a central role in tissue homeostasis. Recent studies show that in addition to monitoring the state of the viscera, they perform efferent functions through the release of small molecules (e.g. peptides like CGRP) that can drive inflammation, thereby contributing to the development of visceral pathologies (e.g. diabetes Razavi, R., Chan, Y., Afifiyan, F.N., Liu, X.J., Wan, X., Yantha, J., Tsui, H., Tang, L., Tsai, S., Santamaria, P., Driver, J.P., Serreze, D., Salter, M.W., Dosch, H.M., 2006. TRPV1+ sensory neurons control beta cell stress and islet inflammation in autoimmune diabetes, Cell 127 1123-1135). Visceral afferents are heterogeneous with respect to their anatomy, neurochemistry and function. They are also highly plastic in that their cellular environment continuously influences their response properties. This plasticity makes them susceptible to long-term changes that may contribute significantly to the development of persistent pain states such as those associated with irritable bowel syndrome, pancreatitis, and visceral cancers. This review examines recent insights into visceral afferent anatomy and neurochemistry and how neonatal insults can affect the function of these neurons in the adult. New approaches to the treatment of visceral pain, which focus on primary afferents, will also be discussed.

Development of galanin-containing nerve fibres in rat tibia

Galanin exerts tonic inhibition of nociceptive input to the central nervous system. Recently, this peptide was demonstrated in several neuronal and non-neuronal structures in bones and joints. In this study, the time of appearance and topographic localization of galanin-containing nerve fibres in bone were studied in rats from gestational day 16 (GD16) to postnatal day 21 (PD21). The tibia was chosen as a model of developing long bone and indirect immunofluorescence combined with confocal laser scanning microscopy was used to identify galanin-immunoreactive (GAL-IR) nerve fibres. The earliest, sparse GAL-IR fibres were observed on GD21 in the perichondrium of both epiphyses and in the periosteum of the diaphysis. From PD1 onwards, GAL-IR fibres were also seen in the bone marrow cavity and in the region of the inter-condylar eminence of the knee joint. Intramedullary GAL-IR fibres in proximal and distal metaphyses appeared around PD1. Some of them accompanied blood vessels, although free fibres were also seen. GAL-IR fibres located in the cartilage canals of both epiphyses were observed from PD7, in the secondary ossification centres from PD10 and in the bone marrow of both epiphyses from PD14. The time course and localization of galanin-containing nerve fibres resemble the development of substance P- and CGRP-expressing nerve fibres, thus suggesting their sensory origin.

A transcriptional network coordinately determines transmitter and peptidergic fate in the dorsal spinal cord

Dorsal horn neurons express many different neuropeptides that modulate sensory perception like the sensation of pain. Inhibitory neurons of the dorsal horn derive from postmitotic neurons that express Pax2, Lbx1 and Lhx1/5, and diversify during maturation. In particular, fractions of maturing inhibitory neurons express various neuropeptides. We demonstrate here that a coordinate molecular mechanism determines inhibitory and peptidergic fate in the developing dorsal horn. A bHLH factor complex that contains Ptf1a acts as upstream regulator and initiates the expression of several downstream transcription factors in the future inhibitory neurons, of which Pax2 is known to determine the neurotransmitter phenotype. We demonstrate here that dynorphin, galanin, NPY, nociceptin and enkephalin expression depends on Ptf1a, indicating that these neuropeptides are expressed in inhibitory neurons. Furthermore, we show that Neurod1/2/6 and Lhx1/5, which act downstream of Ptf1a, control distinct aspects of peptidergic differentiation. In particular, the Neurod1/2/6 factors are essential for dynorphin and galanin expression, whereas the Lhx1/5 factors are essential for NPY expression. We conclude that a transcriptional network operates in maturing dorsal horn neurons that coordinately determines transmitter and peptidergic fate.

PA6-induced human embryonic stem cell-derived neurospheres: a new source of human peripheral sensory neurons and neural crest cells

Human embryonic stem cells (hESC) have been directed to differentiate into CNS cells with clinical importance. However, for study of development and regeneration of the human PNS, and peripheral neuropathies, it would be useful to have a source of human PNS derivatives. We have demonstrated that peripheral sensory neuron-like cells (PSN) can also be derived from hESC via neural crest-like (NC) intermediates, and from neural progenitors induced from hESC using noggin. Here we report the generation of higher purity PSN from passagable neurospheres (NSP) induced by murine PA6 stromal cells. hESC were cultured with PA6, and colonies that developed a specific morphology were cut from the plates. Culture of these colonies under non-adhesive conditions yielded NSPs. Several NC marker genes were expressed in the NSP, and these were also detected in 3-5week gestation human embryos containing migrating NC. These NSPs passaged for 2-8weeks and re-plated on PA6 gave rise to many Brn3a+/peripherin+ cells, characteristic of early sensory-like neurons. Re-culturing PA6-induced NSP cells with PA6 resulted in about 25% of the human cells in the co-cultures differentiating to PSN after 1week, compared to only about 10% PSN obtained after 3 weeks when noggin-induced NSP were used. Two month adherent cultures of PA6-induced NSP cells contained neurons expressing several PSN neuropeptides, and voltage-dependent currents and action potentials were obtained from a molecularly identified PSN. hESC-derived PA6-induced NSP cells are therefore an excellent potential source of human PSN for study of differentiation and modeling of PNS disease.

Postnatal expression of corticotropin releasing factor (CRF) in rat urinary bladder

Corticotropin releasing factor (CRF) is a neuropeptide expressed in micturition reflex circuitry and different roles in these reflexes have been suggested. These studies examined the expression of CRF/CRF receptors in the urinary bladder during postnatal development in the rat. Urinary bladder was harvested from rats (postnatal (P) day 0-adult) euthanized by isoflurane (4%) and thoracotomy. CRF protein expression significantly (p<or=0.01) decreased in the urothelium with increasing postnatal age. In contrast, CRF-immunoreactivity (IR) was increased in nerve fibers in the suburothelial plexus during the second-third postnatal week. Total CRF protein from urinary bladder significantly increased during the second-third postnatal weeks as determined with ELISAs. CRF receptor 2 (CRFR(2)) transcript was expressed in urinary bladder of all postnatal ages examined whereas no CRFR(1) transcript was expressed at any postnatal age examined. We also demonstrated changes in urinary bladder mRNA expression for the neuropeptides, galanin, substance P, vasoactive intestinal polypeptide and pituitary adenylate cyclase activating polypeptide during postnatal development. These studies demonstrate changes in the CRF expression in urinary bladder, specifically in the urothelium and nerve fibers of the suburothelial plexus during postnatal development. Changes in CRF expression and neuropeptide expression in general in the urinary bladder may contribute to the emergence of mature voiding reflexes.

Tlx1 and Tlx3 coordinate specification of dorsal horn pain-modulatory peptidergic neurons

The dorsal spinal cord synthesizes a variety of neuropeptides that modulate the transmission of nociceptive sensory information. Here, we used genetic fate mapping to show that Tlx3(+) spinal cord neurons and their derivatives represent a heterogeneous population of neurons, marked by partially overlapping expression of a set of neuropeptide genes, including those encoding the anti-opioid peptide cholecystokinin, pronociceptive Substance P (SP), Neurokinin B, and a late wave of somatostatin. Mutations of Tlx3 and Tlx1 result in a loss of expression of these peptide genes. Brn3a, a homeobox transcription factor, the expression of which is partly dependent on Tlx3, is required specifically for the early wave of SP expression. These studies suggest that Tlx1 and Tlx3 operate high in the regulatory hierarchy that coordinates specification of dorsal horn pain-modulatory peptidergic neurons.

Estrogen receptor beta is essential for sprouting of nociceptive primary afferents and for morphogenesis and maintenance of the dorsal horn interneurons

Estrogen is known to influence pain, but the specific roles of the two estrogen receptors (ERs) in the spinal cord are unknown. In the present study, we have examined the expression of ERalpha and ERbeta in the spinal cord and have looked for defects in pain pathways in ERbeta knockout (ERbeta(-/-)) mice. In the spinal cords of 10-month-old WT mice, ERbeta-positive cells were localized in lamina II, whereas ERalpha-positive cells were mainly localized in lamina I. In ERbeta(-/-) mice, there were higher levels of calcitonin gene-regulated peptide and substance P in spinal cord dorsal horn and isolectin B4 in the dorsal root ganglion. In the superficial layers of the spinal cord, there was a decrease in the number of calretinin (CR)-positive neurons, and in the outer layer II, there was a loss of calbindin-positive interneurons. During embryogenesis, ERbeta was first detectable in the spinal cord at embryonic day 13.5 (E13.5), and ERalpha was first detectable at E15.5. During middle and later embryonic stages, ERbeta was abundantly expressed in the superficial layers of the dorsal horn. ERalpha was also expressed in the dorsal horn but was limited to fewer neurons. Double staining for ERbeta and CR showed that, in the superficial dorsal horn of WT neonates [postnatal day 0 (P0)], most CR neurons also expressed ERbeta. At this stage, few CR-positive cells were detected in the dorsal horn of ERbeta(-/-) mice. Taken together, these findings suggest that, early in embryogenesis, ERbeta is involved in dorsal horn morphogenesis and in sensory afferent fiber projections to the dorsal horn and that ERbeta is essential for survival of dorsal horn interneurons throughout life.

Adrenomedullin facilitates reinnervation of phenol-injured perivascular nerves in the rat mesenteric resistance artery

Our previous report showed that innervation of calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-containing nerves in rat mesenteric resistance arteries was markedly reduced by topical application of phenol, and that nerve growth factor (NGF) facilitates the reinnervation of both nerves. We also demonstrated that a CGRP superfamily peptide, adrenomedullin, is distributed in perivascular nerves of rat mesenteric resistance arteries. In the present study, we investigated the influence of adrenomedullin on the reinnervation of mesenteric perivascular nerves following topical phenol treatment. Under pentobarbital-Na anesthesia, 8-week-old Wistar rats underwent in vivo topical application of phenol (10% phenol in 90% ethanol) to the superior mesenteric artery proximal to the bifurcation of the abdominal aorta. After the treatment, the animals were subjected to immunohistochemistry of the third branch of small arteries proximal to the intestine and to vascular responsiveness testing on day 7. Topical phenol treatment caused marked reduction of the density of NPY-like immunoreactive (LI)- and CGRP-LI nerve fibers in the arteries. Adrenomedullin (360 or 1000 ng/h) or NGF (250 ng/h), which was administered intraperitoneally for 7 days using an osmotic mini-pump immediately after topical phenol treatment, significantly increased the density of CGRP-LI- and NPY-LI nerve fibers compared with saline. Treatment with adrenomedullin (1000 ng/h) or NGF restored adrenergic nerve-mediated vasoconstriction and CGRP nerve-mediated vasodilation in the perfused mesenteric artery treated topically with phenol. These results suggest that adrenomedullin, like NGF, has a facilitatory effect on the reinnervation of perivascular nerves.

The role of activin in neuropeptide induction and pain sensation

Signals from target tissues play critical roles in the functional differentiation of neuronal cells, and in their subsequent adaptations to peripheral changes in the adult. Sensory neurons in the dorsal root ganglia (DRG) provide an excellent model system for the study of signals that regulate the development of neuronal diversity. DRG have been well characterized and contain both neurons that convey information from muscles about limb position, as well as other neurons that provide sensations from skin about pain information. Sensory neurons involved in pain sensation can be distinguished physiologically and antigenically, and one hallmark characteristic is that these neurons contain neuropeptides important for their functions. The transforming growth factor (TGF) beta family member activin A has recently been implicated in neural development and response to injury. During sensory neuron development, peripheral target tissues containing activin or activin itself can regulate pain neuropeptide expression. Long after development has ceased, skin target tissues retain the capacity to signal neurons about changes or injury, to functionally refine synapses. This review focuses on the role of activin as a target-derived differentiative factor in neural development that has additional roles in response to cutaneous injuries in the adult.

Role of Nitric Oxide in Mediating In Vivo Vascular Responses to Calcitonin Gene-Related Peptide in Essential and Peripheral Circulations in the Fetus

Background— The role of calcitonin gene-related peptide (CGRP) in cardiovascular regulation is gaining clinical and scientific interest. In the adult, in vivo studies have shown that CGRP-stimulated vasodilation in several vascular beds depends, at least in part, on nitric oxide (NO). However, whether CGRP acts as a vasodilator in the fetus in vivo and whether this effect is mediated via NO have been addressed only minimally. This study tested the hypothesis that CGRP has potent NO-dependent vasodilator actions in essential and peripheral vascular beds in the fetus in late gestation.

Methods and Results— Under anesthesia, 5 fetal sheep at 0.8 gestation were instrumented with vascular catheters and Transonic flow probes around an umbilical artery and a femoral artery. Five days later, fetuses received 2- and 5-μg doses of exogenous CGRP intra-arterially in randomized order. Doses were repeated during NO blockade with the NO clamp. This technique permits blockade of de novo synthesis of NO while compensating for tonic production of the gas, thereby maintaining basal cardiovascular function. CGRP resulted in potent and long-lasting NO-dependent dilation in the umbilical and femoral circulations, hypotension, and a positive cardiac chronotropic effect. During NO blockade, the femoral vasodilator response to CGRP was diminished. In contrast, in the umbilical vascular bed, the dilator response was not only prevented but reversed to vasoconstriction.

Conclusions— CGRP has potent NO-dependent vasodilator actions in fetal essential and peripheral vascular beds. CGRP-induced NO-dependent effects in the umbilical vascular bed may provide an important mechanism in the control and maintenance of umbilical blood flow during pregnancy.

Distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)-expressing cells in rat urinary bladder: a developmental study

We examined the distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)(55-102)-immunoreactive (IR) structures in the neonatal and adult rat urinary bladder. Double-labeling studies examining CARTp with tyrosine hydroxylase (TH), neuronal nitric oxide synthase (nNOS), or choline acetyltransferase (ChAT) were performed in wholemounts of urothelium or detrusor or cryostat sections of the bladder. In younger animals (postnatal day [P]1, P3), CARTp-IR cell bodies in detrusor smooth muscle were observed in large clusters ( approximately 100 cells/cluster) at the ureteral insertion and along thick bundles of nerve fibers at the bladder base. The total number of CARTp-IR cells was significantly reduced (by five-fold) at P14, and this reduced number persisted into adulthood. The decrease in the number of CARTp-expressing cells was complemented with positive staining for cleaved caspase-3, suggesting that apoptosis contributed to this decrease. At birth (P1), all CARTp-IR cells expressed the neuronal marker Hu. After birth, CARTp was expressed by some neurons (CARTp-IR, Hu-IR) that represent intramural ganglion cells and by cells that lacked a neuronal phenotype (CARTp-IR, Hu-) but did express TH. Neither of these cell populations expressed ChAT immunoreactivity in adult bladder. These cells (CARTp-IR, Hu-, TH-IR) may represent paraganglion or small intensely fluorescent (SIF) cells. The percentage of colocalization of CARTp-IR and nNOS or TH was dependent on postnatal age and showed an inverse relationship. At P1, 67.1 % of CARTp-IR cells expressed nNOS immunoreactivity. Decreased colocalization was observed with increasing postnatal age. In contrast, 19.5% of CARTp-IR cells expressed TH at P1, but colocalization increased with postnatal age. The suburothelial plexus lacked CARTp-IR nerve fibers until P14, when nerve fibers with varicosities were observed in the urethra and bladder neck region. In summary, we demonstrate 1) a decrease in the number of CARTp-IR cells in rat detrusor in early postnatal development; 2) apoptotic events in the bladder during early postnatal development; 3) rostral migration of CARTp-IR cells from the ureteral insertion toward the bladder body during postnatal development; 4) the presence of different populations of CARTp-IR cells, some with and others without a neuronal phenotype; and (5) age-dependent changes in chemical coding of CARTp-IR cells with postnatal development. This study demonstrates that CARTp-IR intramural ganglia and CARTp-IR paraganglion or SIF cells exist in the postnatal and adult rat bladder, although the role of these cell types remains to be determined.

Differential development of TRPV1-expressing sensory nerves in peripheral organs

In mouse ontogeny, neurons immunoreactive for transient receptor potential vanilloid receptor 1 (TRPV1) were observed primarily in the dorsal root ganglia (DRG) at embryonic day 13 (E13). In the embryonic period, the number of TRPV1(+) neurons decreased, but then gradually increased postnatally. Some of TRPV1(+) neurons were also immunoreactive for calcitonin gene-related peptide (CGRP). At postnatal day 7 (P7), 66% of CGRP(+) neurons were TRPV1(+), and 55% of TRPV1(+) neurons were also CGRP(+) in the L4 DRG. In the peripheral organs, TRPV1-immunorective nerve fibers were transiently observed in the skin at E14. They were also observed in the urinary tract at E14, and in the rectum at E15. Many TRPV1(+) nerve fibers in these organs were also CGRP(+). At P1, TRPV1(+) nerve fibers were observed in the respiratory organs, and to a lesser extent in the stomach, colon, skin, and skeletal muscles. The number of TRPV1(+) nerve fibers on each organ gradually increased postnatally. At P7, TRPV1(+) nerve fibers were also observed in the small intestine and kidneys. The percentage of total TRPV1(+) nerve fibers that co-localized with CGRP was greater in most organs at P7 than at P1. The present results indicate that TRPV1 expression on peripheral processes differs among organs. The differential time course of TRPV1 expression in the cell bodies might be related to the organs to which they project. Co-localization of TRPV1 with CGRP on nerve fibers also varies among organs. This suggests that the TRPV1-mediated neuropeptide release that occurs in certain pathophysiologic conditions also varies among organs.

Calcitonin gene-related peptide and hypertension

Capsaicin-sensitive sensory nerves participate in the regulation of cardiovascular functions both in the normal state and the pathophysiology of hypertension through the actions of potent vasodilator neuropeptides, including calcitonin gene-related peptide (CGRP). CGRP, a very potent vasodilator, is the predominant neurotransmitter in capsaicin-sensitive sensory nerves, and plays an important role in the initiation, progression and maintenance of hypertension via: (1) the alterations in its synthesis and release and/or in vascular sensitivity response to it; (2) interactions with pro-hypertensive systems, including renin-angiotensin-aldosterone system, sympathetic nervous system and endothelin system; and (3) anti-hypertrophy and anti-proliferation of vascular smooth muscle cells. The decrease in CGRP synthesis and release contributes to the elevated blood pressure, as shown in the spontaneously hypertensive rats, alpha-CGRP knockout mice, Dahl-salt or phenol-induced hypertensive rats. In contrast, the increase in CGRP levels or the enhancement of vascular sensitivity response to CGRP plays a beneficial compensatory depressor role in the development of hypertension, as shown in deoxycorticosterone-salt, sub-total nephrectomy-salt, N(omega)-nitro-L-arginine methyl ester or two-kidney, one-clip models of hypertension in rats. We found that rutaecarpine causes a sustained depressor action by stimulation of CGRP synthesis and release via activation of vanilloid receptor subtype 1 (VR1) in hypertensive rats, which reveals the therapeutic implications of VR1 agonists for treatment of hypertension.

The development of nociceptive circuits

The study of pain development has come into its own. Reaping the rewards of years of developmental and molecular biology, it has now become possible to translate fundamental knowledge of signalling pathways and synaptic physiology into a better understanding of infant pain. Research has cast new light on the physiological and pharmacological processes that shape the newborn pain response, which will help us to understand early pain behaviour and to design better treatments. Furthermore, it has shown how developing pain circuitry depends on non-noxious sensory activity in the healthy newborn, and how early injury can permanently alter pain processing.

Corticotropin-releasing factor (CRF) expression in postnatal and adult rat sacral parasympathetic nucleus (SPN)

The neural control of micturition undergoes marked changes during the early postnatal development. During the first few postnatal weeks, the spinal micturition reflex is gradually replaced by a spinobulbospinal reflex pathway that is responsible for micturition in adult animals. Upregulation of brainstem regulation of spinal micturition pathways may contribute to development of mature voiding patterns. We examined the expression of corticotropin-releasing factor (CRF), present in descending projections from Barrington's nucleus to the sacral parasympathetic nucleus (SPN), in postnatal (P0-P36) and adult Wistar rats (P60-90). CRF-immunoreactivity (IR) was present predominantly in the SPN region, although some staining was also observed in the dorsal horn and dorsal commissure in L5-S1 spinal segments. CRF-IR in spinal cord regions was age dependent (R2=0.87-0.98). The majority of the CRF-IR in the lumbosacral spinal cord was eliminated by complete spinalization (2-3 weeks). Double-label immunohistochemistry was combined with quantitative confocal laser scanning microscopy to quantify the number and percentage of colocalization between CRF-immunoreactive varicosities and preganglionic somas or proximal neurites in the SPN in postnatal and adult rats. Results demonstrate an age-dependent upregulation of CRF-IR in the SPN region and specifically in association with preganglionic parasympathetic neurons identified with neuronal nitric oxide synthase (nNOS)-IR. CRF-immunoreactive varicosities on or within a 1 microm perimeter of nNOS-immunoreactive somas or proximal neurites also increased with postnatal age. The upregulation of CRF-IR in bulbospinal projections to the SPN may contribute to mature voiding reflexes.

Galaninergic mechanisms at the spinal level: focus on histochemical phenotyping

The 29/30 amino acid neuropeptide galanin is present in a small population of DRG neurons under normal condition but is strongly upregulated after nerve injury. There is evidence that this upregulated galanin has trophic actions, for example promoting neurite outgrowth as well as influencing pain processing. In fact, both pro- and antinociceptive effects have been reported, probably relating to activation of different receptors. It has been proposed that presynaptic GalR2 receptors are pro-nociceptive by enhancing release of excitatory transmitters in the dorsal horn, and anti-nociceptive via an action on GalR1-positive interneurons. These neurons have recently been shown to be glutamatergic. Several other peptides and molecules are also regulated by nerve injury. Here we focus on neuropeptide tyrosine (NPY), which is upregulated in parallel with galanin. We review data reporting on coexistence between galanin and NPY and between these two peptides and the two NPY receptors Y1 and Y2. The data show considerable overlap, and it will be an important task to analyse how cross-talk between these neuropeptides can influence pain processing. It is proposed that such cross-talk can occur by release of peptides from DRGs neuron somata within dorsal root ganglia. To what extent these mechanisms shown to exist in rodents also occur in human is important, if one wants to discuss novel strategies for pain treatment on the basis of these findings. So far information is limited, but it has been demonstrated that galanin is expressed in DRGs and possibly also regulated.

Effects of systemically administered NT-3 on sensory neuron loss and nestin expression following axotomy

Previous work has shown that administration of the neurotrophin NT-3 intrathecally or to the proximal stump can prevent axotomy-induced sensory neuron loss and that NT-3 can stimulate sensory neuron differentiation in vitro. We have examined the effect of axotomy and systemic NT-3 administration on neuronal loss, apoptosis (defined by morphology and activated caspase-3 immunoreactivity), and nestin expression (a protein expressed by neuronal precursor cells) in dorsal root ganglia (DRG) following axotomy of the adult rat sciatic nerve. Systemic administration of 1.25 or 5 mg of NT-3 over 1 month had no effect on the incidence of apoptotic neurons but prevented the overall loss of neurons seen at 4 weeks in vehicle-treated animals. Nestin-immunoreactive neurons began to appear 2 weeks after sciatic transection in untreated animals and steadily increased in incidence over the next 6 weeks. NT-3 administration increased the number of nestin-immunoreactive neurons at 1 month by two- to threefold. Nestin-IR neurons had a mean diameter of 20.78 +/- 2.5 microm and expressed the neuronal markers neurofilament 200, betaIII-tubulin, protein gene product 9.5, growth associated protein 43, trkA, and calcitonin gene-related peptide. Our results suggest that the presence of nestin in DRG neurons after nerve injury is due to recent differentiation and that exogenous NT-3 may prevent neuron loss by stimulating this process, rather than preventing neuron death.

Postnatal changes in the spatial distributions of substance P and neurokinin-1 receptor in the trigeminal subnucleus caudalis of mice

Nociceptive afferent signals from the orofacial area are transmitted to the trigeminal subnucleus caudalis (Vc) through the release of glutamate and/or substance P (SP). Although nociceptive transmission and/or modulating mechanisms are known to develop during the postnatal period, the specific developmental changes in nociception and/or modulation remain unclear. The present study examined postnatal changes in the spatial relationship between SP and its receptor, the NK1 receptor (NK1R), in the mouse Vc by immunohistochemistry and quantitative analysis. The medulla was removed from C57BL/6N mice (1, 2, 4, and 8 weeks of age) after perfusion and fixation, and cut horizontally at a thickness of 40 mum. The relative densities of SP- and NK1R-immunoreactive areas and their changes with age were assessed statistically. One- and 2-week-old mice showed relatively high densities of SP-positive structures in the marginal layer (Mar) and the deep part of the magnocellular layer (Mag). The SP distribution in the superficial Vc remained unchanged, but the density in the deep Mag gradually decreased with age, resulting in a complete loss after postnatal week 4. The NK1R-immunoreactivity exhibited a similar distribution pattern to that of SP, but the pattern remained unchanged during the postnatal period. Double-immunofluorescence staining for SP and NK1R demonstrated only moderate direct contact of SP-positive structures with NK1R in the superficial area. These separate distributions and the postnatal changes in SP and NK1R suggest the possibility of another nociceptive afferent transmission mechanism, that is, volume transmission, in the Vc other than synapse-mediated transmission.

Expression of spinal cord Fos protein in response to intrathecal adrenomedullin and CGRP in conscious rats

Adrenomedullin (AM) immunoreactivity and mRNA, in addition to a large number of specific AM-binding sites, exist in the rat spinal cord. However, no phenotype has been reported for AM in the spinal cord. Here, expression of c-fos in response to intrathecal (i.t.) administration of AM, proadrenomedullin N-terminal 20 peptide (PAMP) and calcitonin gene-related peptide (CGRP) was examined in the thoracic, lumbar and sacral regions of spinal cord in conscious rats. Two hours after i.t. administration of either CGRP (2.5 and 10 microg) or AM (10 microg), the number of c-Fos immunoreactive nuclei was increased in all the spinal regions examined in this study, with the highest increase observed in the superficial dorsal horn. Few cells with c-fos immunoreactivity were found in the spinal cord of rats 2 h after i.t. injection of either saline or PAMP. Effects of AM (10 microg) and CGRP (2.5 microg) on c-fos expression were blocked when rats were pretreated with 40 microg of intrathecal CGRP8-37 (CGRP1 receptor antagonist). Fos-like immunoreactivity induced by i.t. CGRP and/or AM were also significantly abolished by i.t. administration of the nitric oxide (NO) inhibitor, l-NAME, indicating that endogenous NO is a necessary intermediary in CGRP and AM induced c-fos expression in the rat spinal cord. In conclusion, AM induces c-fos expression in rat spinal cord when administered intrathecally, with the pattern being similar to those produced by i.t. CGRP. Effects of the two peptides are sensitive to CGRP8-37 and l-NAME.

Mesenteric arterial relaxation to calcitonin gene-related peptide is increased during pregnancy and by sex steroid hormones

The present study investigated whether pregnancy and circulatory ovarian hormones increase the sensitivity of the mesenteric artery to calcitonin gene-related peptide (CGRP)-induced relaxation and possible mechanisms involved in this process. Mesenteric arteries from young adult male rats or female rats (during estrous cycle, after ovariectomy, at Day 20 of gestation, or Postpartum Day 2) were isolated, and the responsiveness of the vessels to CGRP was examined with a small vessel myograph. The CGRP (10(-10) to 10(-7) M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in mesenteric arteries of all groups. Arterial relaxation sensitivity to CGRP was significantly (P < 0.05) greater in female rats compared with male rats. Pregnancy increased the sensitivity to CGRP significantly (P < 0.05) compared to ovariectomized and Postpartum Day 2 rats. In pregnant rats, CGRP-receptor antagonist, CGRP(8-37), inhibited the relaxation responses produced by CGRP. The CGRP-induced relaxation was not affected by N(G)-nitro-l-arginine methyl ester (nitric oxide inhibitor, 10(-4) M) but was significantly (P < 0.05) attenuated by an inhibitor of guanylate cyclase (1H-[1 , 2 , 4 ]oxadizaolo[4 , 3 -a]quinoxalin-1-one, 10(-5) M). Relaxation responses of CGRP on mesenteric arteries were blocked (P < 0.05) by a cAMP-dependent protein kinase A inhibitor, Rp-cAMPs (10(-5) M). The CGRP-induced vasorelaxation was significantly (P < 0.05) attenuated by calcium-dependent (tetraethylammonium, 10(-3) M), but not ATP-sensitive (glybenclamide, 10(-5) M), potassium channel blocker. Therefore, the results of the present study suggest that mesenteric vascular sensitivity to CGRP is higher during pregnancy and that cAMP, cGMP, and calcium-dependent potassium channels appear to be involved. Therefore, we propose that CGRP-mediated vasodilation may be important to maintain vascular adaptations during pregnancy.

Pain and stress in the human fetus

It is not known if the fetus can actually feel pain, but noxious stimulation during fetal life does cause detectable stress responses. These responses cause both short and long-term changes in the central nervous system, which can affect subsequent pain behaviour. Reducing the stress response is known to be beneficial in children and adults and recent evidence suggests this is also true for the fetus. However, the optimal amount of suppression required and the best method of achieving this (opioid or regional anaesthesia techniques) remain unknown. Prevention and treatment of pain is a basic human right, regardless of age, and if the technique of fetal surgery is to progress then a greater understanding of nociception and the stress response is required.

Characterization of long-term mouse brain aggregating cultures: Evidence for maintenance of neural precursor cells

An extensive characterization of fetal mouse brain cell aggregates has been performed using immunohistochemical and stereological methods. Single cell suspensions from mechanically dissociated cortex and hippocampus were cultured in serum-free, B27-supplemented medium under constant gyratory agitation for up to 56 days. Three-dimensional aggregates started to form immediately after seeding and reached a final average size of 500 microm in diameter. Among the cell types identified, neurons were the most abundant cells in the aggregates, followed by astrocytes, microglia, and oligodendrocytes. Western blotting for synaptophysin and immunostaining for neurotransmitter-related molecules indicated the presence of well-defined phenotypic characteristics of the neurons in this culture system, suggesting functionality. Proliferating cells, many with neural precursor cell properties, were seen throughout the culture period and could be isolated from the aggregates even after 2 months in culture. Neural precursor cells were isolated from the aggregates after more than 1 month in culture; these cells were successfully differentiated into neurons, astrocytes, and oligodendrocytes. The aggregate culture system may provide a versatile tool for molecular dissection of processes identified in mouse models, including transgenic animals and manipulation of neural precursor cells.

Female Sex Steroid Hormones and Pregnancy Regulate Receptors for Calcitonin Gene-Related Peptide in Rat Mesenteric Arteries, but Not in Aorta1

Calcitonin gene-related peptide (CGRP) is a potent vasodilator neuropeptide known to be involved in the regulation of vascular tone. Results of previous studies from our laboratory and others suggest that vascular sensitivity to CGRP is enhanced during pregnancy and that the female sex steroid hormones estradiol-17beta (E2) and progesterone (P4) may be involved in this process. We hypothesized that CGRP receptors in the mesenteric artery are increased during pregnancy and with sex steroid hormone treatments. In the present study, we investigated whether pregnancy and female sex steroid hormones modulate the CGRP-receptors CGRP-A and CGRP-B in the mesenteric artery in the rat. The CGRP-A receptor consists of calcitonin receptor-like receptor (CRLR) and receptor activity-modifying protein 1 (RAMP1); however, the CGRP-B receptor needs to be further characterized. Messenger RNA levels for CRLR and RAMP1 were assessed by reverse transcription-polymerase chain reaction, and CGRP-B receptor proteins levels were determined by Western blot analysis. In addition, [125I]CGRP binding was measured by Scatchard analysis. Both mRNA for CGRP-A (CRLR and RAMP1) and the protein for CGRP-B receptors in mesenteric arteries were increased with pregnancy compared to nonpregnant, diestrous animals. A P4 antagonist, RU-486, downregulated and P4 upregulated these receptors in mesenteric arteries (P < 0.05) in pregnant rats. In adult ovariectomized rats, P4 upregulated CRLR and RAMP1 mRNA levels as well as [125I]CGRP-binding sites. The CGRP-B-receptor protein levels were significantly (P < 0.05) elevated by P4 and by combined E2 and P4 treatment. Together with earlier findings, these data suggest that increases in the expression of CGRP-A (CRLR and RAMP1) and CGRP-B receptors in mesenteric arteries may be important in reducing vascular resistance and in vascular adaptations that occur during pregnancy; in addition, P4 may be involved in this process.