Noradrenergic Fibers Research Articles

Noradrenalin and dopamine receptors both control cAMP-PKA signaling throughout the cerebral cortex.

Noradrenergic fibers innervate the entire cerebral cortex, whereas the cortical distribution of dopaminergic fibers is more restricted. However, the relative functional impact of noradrenalin and dopamine receptors in various cortical regions is largely unknown. Using a specific genetic label, we first confirmed that noradrenergic fibers innervate the entire cortex whereas dopaminergic fibers were present in all layers of restricted medial and lateral areas but only in deep layers of other areas. Imaging of a genetically encoded sensor revealed that noradrenalin and dopamine widely activate PKA in cortical pyramidal neurons of frontal, parietal and occipital regions with scarce dopaminergic fibers. Responses to noradrenalin had higher amplitude, velocity and occurred at more than 10-fold lower dose than those elicited by dopamine, whose amplitude and velocity increased along the antero-posterior axis. The pharmacology of these responses was consistent with the involvement of Gs-coupled beta1 adrenergic and D1/D5 dopaminergic receptors, but the inhibition of both noradrenalin and dopamine responses by beta adrenergic antagonists was suggestive of the existence of beta1-D1/D5 heteromeric receptors. Responses also involved Gi-coupled alpha2 adrenergic and D2-like dopaminergic receptors that markedly reduced their amplitude and velocity and contributed to their cell-to-cell heterogeneity. Our results reveal that noradrenalin and dopamine receptors both control cAMP-PKA signaling throughout the cerebral cortex with moderate regional and laminar differences. These receptors can thus mediate widespread effects of both catecholamines, which are reportedly co-released by cortical noradrenergic fibers beyond the territory of dopaminergic fibers.

Lower urinary tract function in spinal cord-injured rats: midthoracic contusion versus transection.

To compare changes in lower urinary tract (LUT) function with modifications in pathways that regulate LUT function using two different animal models (incomplete and complete) of spinal cord injury (SCI). Female Sprague-Dawley rats were used. SCI was made at Th8/9 by a contusion injury (contusion, n=9) or a complete transection (transection, n=9). Unoperated rats were used as normal controls (normal, n=6). LUT function was evaluated by micturition behavior in metabolic cages for 24 h and cystometry in awake animals. Immunocytochemical staining at the L6 spinal cord, spinal areas associated with LUT, was performed to identify descending modulatory fibers and dorsal root afferents that project to the L6 spinal cord. Volume/micturition in metabolic cages gradually increased in both contusion and transection groups compared with normals, and operated groups did not differ from each other. Urodynamic parameters from cystometry were significantly different in contusion and transection groups compared with normals, but again there was no significant difference between contusion and transection groups. Immunocytochemical analyses at the L6 spinal cord showed no serotonergic or noradrenergic fibers in transection group, but some descending fibers remained in contusion group, indicating sparing. Small dorsal root afferents were denser in both contusion and transection groups than in normals, indicating sprouting. Although differences were not found in LUT function in operated animals, supraspinal and dorsal root projections to the L6 spinal cord responded differently to contusion and transection. This suggests that the benefits of pharmacologic treatments may be different in two lesion models.

Effect of neurturin deficiency on cholinergic and catecholaminergic innervation of the murine eye

Neurturin (NRTN) is a neurotrophic factor required for the development of many parasympathetic neurons and normal cholinergic innervation of the heart, lacrimal glands and numerous other tissues. Previous studies with transgenic mouse models showed that NRTN is also essential for normal development and function of the retina (J. Neurosci. 28:4123–4135, 2008). NRTN knockout (KO) mice exhibit a marked thinning of the outer plexiform layer (OPL) of the retina, with reduced abundance of horizontal cell dendrites and axons, and aberrant projections of horizontal cells and bipolar cells into the outer nuclear layer. The effects of NRTN deletion on specific neurotransmitter systems in the retina and on cholinergic innervation of the iris are unknown. To begin addressing this deficiency, we used immunohistochemical methods to study cholinergic and noradrenergic innervation of the iris and the presence and localization of cholinergic and dopaminergic neurons and nerve fibers in eyes from adult male wild-type (WT) and NRTN KO mice (age 4–6 months). Mice were euthanized, and eyes were removed and fixed in cold neutral buffered formalin or 4% paraformaldehyde. Formalin-fixed eyes were embedded in paraffin, and 5 μm cross-sections were collected. Representative sections were stained with hematoxylin and eosin or processed for fluorescence immunohistochemistry after treatment for antigen retrieval. Whole mount preparations were dissected from paraformaldehyde fixed eyes and used for immunohistochemistry. Cholinergic and catecholaminergic nerve fibers were labeled with primary antibodies to the vesicular acetylcholine transporter (VAChT) and tyrosine hydroxylase (TH), respectively. Cholinergic and dopaminergic cell bodies were labeled with antibodies to choline acetyltransferase (ChAT) and TH, respectively. Cholinergic innervation of the mouse iris was restricted to the sphincter region, and noradrenergic fibers occurred throughout the iris and in the ciliary processes. This pattern was unaffected by deletion of NRTN. Furthermore, functional experiments demonstrated that cholinergic regulation of the pupil diameter was retained in NRTN KO mice. Hematoxylin and eosin stains of the retina confirmed a marked thinning of the OPL in KO mice. VAChT and ChAT staining of the retina revealed two bands of cholinergic processes in the inner plexiform layer, and these were unaffected by NRTN deletion. Likewise, NRTN deletion did not affect the abundance of ChAT-positive ganglion and amacrine cells. In marked contrast, staining for TH showed an increased abundance of dopaminergic processes in the OPL of retina from KO mice. Staining of retinal whole mounts for TH showed no difference in the abundance of dopaminergic amacrine cells between WT and KO mice. These findings demonstrate that the neurotrophic factor NRTN is not required for the development or maintenance of cholinergic innervation of the iris, cholinergic control of pupil diameter, or for development of cholinergic and dopaminergic amacrine cells of the retina. However, NRTN deficiency causes a marked reduction in the size of the OPL and aberrant growth of dopaminergic processes into this region.

The peritoneum—an important factor for pathogenesis and pain generation in endometriosis

Endometriosis (EM) is an oestrogen-dependent disease affecting 10-15 % of women during reproductive age. It is characterised by the presence of endometrial glands, stromal- and smooth muscle-like cells outside of the uterine cavity. Fifty to sixty per cent of women and teenage girls with pelvic pain suffer from EM. EM causes disability and compromises the quality of life in women and young girls significantly. Pain generation in EM is an intricate interplay of several factors such as the endometriotic lesions themselves and the pain-mediating substances, nerve fibres and cytokine-releasing immune cells such as macrophages. These interactions seem to induce a neurogenic inflammatory process. Recently published data demonstrated an increased peptidergic and decreased noradrenergic nerve fibre density in peritoneal lesions. These data could be substantiated by in vitro analyses demonstrating that the peritoneal fluids of patients suffering from EM induced an enhanced sprouting of sensory neurites from chicken dorsal root ganglia and decreased neurite outgrowth from sympathetic ganglia. These findings might be directly involved in the perpetuation of inflammation and pain. Furthermore, the evidence of EM-associated smooth muscle-like cells seems another important factor in pain generation. The peritoneal endometriotic lesion leads to reactions in the surrounding tissue and, therefore, is larger than generally believed. The identification of EM-associated nerve fibres and smooth muscle-like cells fuel discussions on the mechanisms of pain generation in EM, and may present new targets for innovative treatments.

Localization of α7 nicotinic acetylcholine receptor mRNA and protein within the cholinergic anti-inflammatory pathway

Electrical stimulation of the vagus nerve attenuates tumor necrosis factor (TNF) synthesis by macrophages and reduces the systemic inflammatory response. Current evidence suggests that the α7 nicotinic acetylcholine receptor present in the celiac/superior mesenteric ganglia is a key component in vagus nerve signaling to the spleen; however, there is currently no direct anatomical evidence that the α7 receptor is present in the murine celiac/superior mesenteric ganglia. Our study addresses this deficiency by providing anatomical evidence that the α7 receptor is expressed within the celiac/superior mesenteric ganglia and splenic nerve fibers using immunohistochemistry and quantitative polymerase chain reaction (qPCR). α7 receptor mRNA is highly expressed in the celiac/superior mesenteric ganglia and at low levels in the spleen compared to the brain. Double-labeling for α7 and tyrosine hydroxylase shows that α7 receptor protein is present on noradrenergic neurons within the ganglia and prejunctionally on noradrenergic nerve fibers within the spleen. The α7 receptor in the ganglia provides a possible location for the action of α7-selective agonists, while prejunctional α7 receptor expressed on splenic nerves may induce an increase in norepinephrine release in a positive feedback system enhanced by lymphocyte-derived acetylcholine.

Noradrenergic Sympathetic Sprouting and Cholinergic Reinnervation Maintains Non-Amyloidogenic Processing of AβPP

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) plaques, hyperphosphorylated tau neurofibrillary tangles, and cholinergic dysfunction. Cholinergic degeneration can be mimicked in rats by lesioning medial septum cholinergic neurons. Hippocampal cholinergic denervation disrupts retrograde nerve growth factor (NGF) transport, leading to its accumulation, which subsequently triggers sprouting of noradrenergic sympathetic fibers from the superior cervical ganglia into hippocampus. Previously we reported that coincident with noradrenergic sprouting is the partial reinnervation of hippocampus with cholinergic fibers and the maintenance of a M1 muscarinic acetylcholine receptor (M1 mAChR) dependent long-term depression at CA3-CA1 synapses that is lost in the absence of sprouting. These findings suggest that sympathetic sprouting and the accompanying cholinergic reinnervation maintains M1 mAChR function. Importantly, noradrenergic sympathetic and cholinergic sprouting have been demonstrated in human postmortem AD hippocampus. Furthermore, M1 mAChRs are a recent focus as a therapeutic target for AD given their role in cognition and non-amyloidogenic processing of amyloid-β protein precursor (AβPP). Here we tested the hypotheses that noradrenergic sympathetic sprouting is triggered by NGF, that sprouting maintains non-amyloidogenic AβPP processing, and that sprouting is prevented by intrahippocampal Aβ42 infusion. We found that NGF stimulates sprouting, that sprouting maintains non-amyloidogenic AβPP processing, and that Aβ42 is not only toxic to central cholinergic fibers innervating hippocampus but it prevents and reverses noradrenergic sympathetic sprouting and the accompanying cholinergic reinnervation. These findings reiterate the clinical implications of sprouting as an innate compensatory mechanism and emphasize the importance of M1 mAChRs as an AD therapeutic target.

Increased density of inhibitory noradrenergic parenchymal nerve fibers in hypertrophic islets of Langerhans of obese mice

Background and aimWe sought to identify mechanisms of beta cell failure in genetically obese mice. Little is known about the role of pancreatic innervation in the progression of beta cell failure. In this work we studied adrenergic innervation, in view of its potent inhibitory effect on insulin secretion. We analyzed genetically obese ob/ob and db/db mice at different ages (6- and 15-week-old), corresponding to different compensatory stages in the course of beta cell dysfunction. 15 week-old HFD mice were also studied. Methods and resultsAll mice were characterized by measures of plasma glucose, insulin, and HOMA. After perfusion, pancreata were dissected and studied by light microscopy, electron microscopy, and morphometry. Insulin, Tyrosine Hydroxylase-positive fibers and cells and Neuropeptide Y-positive cells were scored by immunohistochemistry.Islets of obese mice showed increased noradrenergic fiber innervation, with significant increases of synaptoid structures contacting beta cells compared to controls. Noradrenergic innervation of the endocrine area in obese db/db mice tended to increase with age, as diabetes progressed. In ob/ob mice, we also detected an age-dependent trend toward increased noradrenergic innervation that, unlike in db/db mice, was unrelated to glucose levels. We also observed a progressive increase in Neuropeptide Y-immunoreactive elements localized to the islet core. ConclusionsOur data show increased numbers of sympathetic nerve fibers with a potential to convey inhibitory signals on insulin secretion in pancreatic islets of genetically obese animals, regardless of their diabetic state. The findings suggest an alternative interpretation of the pathogenesis of beta cell failure, as well as novel strategies to reverse abnormalities in insulin secretion.

6. Osteoclast progenitors induce catecholaminergic-to-cholinergic transition of sympathetic nerve fibers under healthy conditions

Sympathetic nerve fibers innervate bone and tissue adjacent to joints. They play an important role in bone and tissue homeostasis. Under certain conditions, sympathetic nerve fibers can change their phenotype from catecholaminergic to cholinergic. This can be important because anti-inflammatory effects of acetylcholine have been described (alpha-7-nicotinic receptor). We asked whether this transition might occur in the joint during collagen-induced arthritis (CIA) in mice or during rheumatoid arthritis (RA) and osteoarthritis (OA) in humans. Sections of limbs from 30 immunized mice and synovial tissue samples obtained from 30 OA and 12 RA patients were stained for tyrosine hydroxylase (noradrenergic fibers), and for vesicular acetylcholine transporter (cholinergic fibers). In mouse joint area, an increase in the ratio of cholinergic to catecholaminergic nerve fibers appeared at day 35 after immunization. Most of the nerve fibers were located in joint-adjacent skin or muscle tissue, and only very few were detected in synovial tissue or near erosions. In human tissue sections, we were able to show cholinergic fibers in the synovium of four OA patients but in none of the RA patients. Co-culture of sympathetic ganglia and osteoclast progenitors from healthy mice showed more catecholaminergic-to-cholinergic transition when compared to experiments with osteoclast progenitors from arthritic mice. In mice and men, catecholaminergic-to-cholinergic transition is possible in less synovial inflamed tissue but not in highly inflamed arthritic tissue.

Degenerative alterations in noradrenergic neurons of the locus coeruleus in Alzheimer's disease.

Mice carrying mutant amyloid-β precursor protein and presenilin-1 genes (APP/PS1 double transgenic mice) have frequently been used in studies of Alzheimer's disease; however, such studies have focused mainly on hippocampal and cortical changes. The severity of Alzheimer's disease is known to correlate with the amount of amyloid-β protein deposition and the number of dead neurons in the locus coeruleus. In the present study, we assigned APP/PS1 double transgenic mice to two groups according to age: young mice (5–6 months old) and aged mice (16–17 months old). Age-matched wild-type mice were used as controls. Immunohistochemistry for tyrosine hydroxylase (a marker of catecholaminergic neurons in the locus coeruleus) revealed that APP/PS1 mice had 23% fewer cells in the locus coeruleus compared with aged wild-type mice. APP/PS1 mice also had increased numbers of cell bodies of neurons positive for tyrosine hydroxylase, but fewer tyrosine hydroxylase-positive fibers, which were also short, thick and broken. Quantitative analysis using unbiased stereology showed a significant age-related increase in the mean volume of tyrosine droxylase-positive neurons in aged APP/PS1 mice compared with young APP/PS1 mice. Moreover, the mean volume of tyrosine hydroxylase-positive neurons was positively correlated with the total volume of the locus coeruleus. These findings indicate that noradrenergic neurons and fibers in the locus coeruleus are predisposed to degenerative alterations in APP/PS1 double transgenic mice.

The Noradrenergic Innervation and Steroidogenic Activity of Porcine Cystic Ovaries

The aim of the present study was to investigate the distribution and density of noradrenergic nerve fibres (NNFs), content of catecholamines (CATs) and steroids in the cystic ovaries of gilts receiving DXM from middle luteal phase. Cystic status of ovaries was induced by i.m. DXM injections on days 7-21 of the estrous cycle. During the same time, gilts in the control group received saline. The ovaries were collected on predicted day 11 of the second studied estrous cycle. The cystic ovaries were supplied by more numerous NNFs than the control gonads. Moreover after DXM injections, the content of CATs and progesterone and androstendione (A(4)) in the cystic wall were elevated, while the levels of A(4), testosterone and estradiol-17beta in the cystic fluid were lowered. Our results show that in the porcine cystic ovaries, induced by DXM injections from middle phase of estrous cycle, increased the density of NNFs and level of CATs, and that it was accompanied by changes in the content of steroids. Moreover, this study is a further confirmation that the morphological and functional changes of cystic ovaries are partly dependent on phase of the estrous cycle in which the induction of the ovarian cysts was initiated.

Effects of Stimulation of Nerve Fibers on the Contractile Activity of Tracheobronchial Lymph Node Capsule Smooth Muscles

The contractile activity of smooth muscle in the capsules of bovine tracheobronchial lymph nodes was recorded. On electrical stimulation with a field (impulse amplitude 55 V, duration 0.5 msec, frequency 0.5, 1, 2, 4, 8, 16, and 32 Hz), strips of lymph node capsule showed frequency-dependent increases in tone and phasic contraction frequency. Reactions evoked by electrical stimulation were significantly (by 80%) suppressed by tetrodotoxin (10–6 M). Blockade of M-cholinoreceptors with atropine did not lead to any change in the effects of stimulation. The contractile response of preparations to electrical stimulation on the background of phentolamine (10–7–10–6 M) were significantly suppressed but not completely prevented. Propranolol (10–7–10–6 M) did not alter or slightly increased the contractile responses of lymph node capsules to electrical stimulation. These data lead to the conclusion that the contractile activity of tracheobronchial lymph node capsule smooth muscle is modulated (at least partially) by excitatory noradrenergic nerve fibers.

DSP-4, a noradrenergic neurotoxin, produces sex-specific effects on pairing and courtship behavior in zebra finches

Norepinephrine (NE) is involved in a variety of behaviors across vertebrate species. In songbirds, NE is involved in singing and auditory perception, fundamental components of pair formation. Mechanisms of pairing remain poorly understood in avian species. NE is likely involved given its role in vocal communication and perception. Here, we tested the hypothesis that DSP-4 treatments (a noradrenergic neurotoxin that decreases NE) decreases singing in males, song perception in females and pairing in both sexes using a naturalistic paradigm. Females were tested for preferences of either control or DSP-4 males in a two-choice paradigm using live males. Both sexes were then tested for courtship and pair formation in aviaries. In the two-choice paradigm, control females showed a significant preference for control males over DSP-4 males, whereas DSP-4 females showed no such preference. In the aviary tests, DSP-4 males engaged in less courtship behavior, showed decreased pairing behaviors and increased pair latencies compared to control males. In females, DSP-4 treatments did not alter courtship or pairing behavior. Lower neural densities of noradrenergic fibers in song, auditory, and affiliative regions were observed in DSP-4 animals of both sexes. Furthermore, DBH-ir densities in these regions explained variations in courtship and pairing behaviors, as well as pairing status. Our results extend previous findings to naturalistic contexts, provide evidence that DBH-ir densities in specific regions correlate with pairing-related behaviors, and inform us of sex differences in the role of NE in pairing.

Effect of the denervation of porcine ovaries on dexamethasone-induced cyst formation

Previously, we have shown that the activity of noradrenergic nerve fibres increased and the steroid content changed in porcine ovaries with dexamethasone-(DXM-) induced polycystic status. To better understand the role of the ovarian nerves in the formation of cystic status, the morphology and steroidogenic activity of the ovaries of DXM-treated gilts after denervation of the gonads were investigated in this study. Ovarian denervation was performed on day 3 of the first studied oestrous cycle and then, on days 7-21 of the cycle, DXM was administered. Following neurectomy and DXM treatment, cysts, medium-sized follicles and corpora lutea were not present, while the number of small-sized follicles increased. Denervation and DXM application led to a reduction in the number of dopamine-β-hydroxylase- and/or neuropeptide Y-immunoreactive nerve fibres. The concentrations of progesterone, androstenedione, testosterone and oestradiol-17β in the follicular fluid and/or in the wall of small-sized follicles of the experimental gilts were lower than in the controls. A similar result was demonstrated for P450scc, 3β-HSD and P450arom protein contents in the small follicles. Our data showed that DXM was not able to stimulate the formation of cysts in denervated porcine ovaries, indicating that the ovarian peripheral nerves might participate in the aetiopathogenesis of polycystic status.

Evidence for a regional specificity in the density and distribution of noradrenergic varicosities in rat cortex.

The brainstem nucleus locus coeruleus (LC) is the sole source of norepinephrine (NE)-containing fibers in the mammalian cortex. Previous studies suggest that the density of noradrenergic fibers in rat is relatively uniform across cortical regions and that cells in the nucleus discharge en masse. This implies that activation of the LC results in equivalent release of NE throughout the cortex. However, it is possible that there could be differences in the density of axonal varicosities across regions, and that these differences, rather than a difference in fiber density, may contribute to the regulation of NE efflux. Quantification of dopamine β-hydroxylase (DβH)-immunostained varicosities was performed on several cortical regions and in the ventral posterior medial (VPM) thalamus by using unbiased sampling methods. The density of DβH varicosities is greater in the prefrontal cortex than in motor, somatosensory, or piriform cortices, greater in superficial than in deep layers of cortex, and greater in the VPM than in the somatosensory cortex. Our results provide anatomical evidence for non-uniform release of NE across functionally discrete cortical regions. This morphology may account for a differential, region-specific, impact of LC output on different cortical areas.

Testosterone alters genomic responses to song and monoaminergic innervation of auditory areas in a seasonally breeding songbird

Behavioral responses to social stimuli often vary according to endocrine state. Our previous work has suggested that such changes in behavior may be due in part to hormone-dependent sensory processing. In the auditory forebrain of female white-throated sparrows, expression of the immediate early gene ZENK (egr-1) is higher in response to conspecific song than to a control sound only when plasma estradiol reaches breeding-typical levels. Estradiol also increases the number of detectable noradrenergic neurons in the locus coeruleus and the density of noradrenergic and serotonergic fibers innervating auditory areas. We hypothesize, therefore, that reproductive hormones alter auditory responses by acting on monoaminergic systems. This possibility has not been examined in males. Here, we treated non-breeding male white-throated sparrows with testosterone to mimic breeding-typical levels and then exposed them to conspecific male song or frequency-matched tones. We observed selective ZENK responses in the caudomedial nidopallium only in the testosterone-treated males. Responses in another auditory area, the caudomedial mesopallium, were selective regardless of hormone treatment. Testosterone treatment reduced serotonergic fiber density in the auditory forebrain, thalamus, and midbrain, and although it increased the number of noradrenergic neurons detected in the locus coeruleus, it reduced noradrenergic fiber density in the auditory midbrain. Thus, whereas we previously reported that estradiol enhances monoaminergic innervation of the auditory pathway in females, we show here that testosterone decreases it in males. Mechanisms underlying testosterone-dependent selectivity of the ZENK response may differ from estradiol-dependent ones

White-to-brown transdifferentiation of omental adipocytes in patients affected by pheochromocytoma

In all mammals, white adipose tissue (WAT) and brown adipose tissue (BAT) are found together in several fat depots, forming a multi-depot organ. Adrenergic stimulation induces an increase in BAT usually referred to as “browning”. This phenomenon is important because of its potential use in curbing obesity and related disorders; thus, understanding its cellular mechanisms in humans may be useful for the development of new therapeutic strategies. Data in rodents have supported the direct transformation of white into brown adipocytes. Biopsies of pure white omental fat were collected from 12 patients affected by the catecholamine-secreting tumor pheochromocytoma (pheo-patients) and compared with biopsies from controls. Half of the omental fat samples from pheo-patients contained uncoupling protein 1 (UCP1)-immunoreactive-(ir) multilocular cells that were often arranged in a BAT-like pattern endowed with noradrenergic fibers and dense capillary network. Many UCP1-ir adipocytes showed the characteristic morphology of paucilocular cells, which we have been described as cytological marker of transdifferentiation. Electron microscopy showed increased mitochondrial density in multi- and paucilocular cells and disclosed the presence of perivascular brown adipocyte precursors. Brown fat genes, such as UCP1, PR domain containing 16 (PRDM16) and β3-adrenoreceptor, were highly expressed in the omentum of pheo-patients and in those cases without visible morphologic re-arrangement. Of note, the brown determinant PRDM16 was detected by immunohistochemistry only in nuclei of multi- and paucilocular adipocytes. Quantitative electron microscopy and immunohistochemistry for Ki67 suggest an unlikely contribution of proliferative events to the phenomenon. The data support the idea that, in adult humans, white adipocytes of pure white fat that are subjected to adrenergic stimulation are able to undergo a process of direct transformation into brown adipocytes. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.

The puerperium alters spinal cord plasticity following peripheral nerve injury

Tissue and nerve damage can result in chronic pain. Yet, chronic pain after cesarean delivery is remarkably rare in women and hypersensitivity from peripheral nerve injury in rats resolves rapidly if the injury occurs in the puerperium. Little is known regarding the mechanisms of this protection except for a reliance on central nervous system oxytocin signaling. Here we show that the density of inhibitory noradrenergic fibers in the spinal cord is greater when nerve injury is performed in rats during the puerperium, whereas the expression of the excitatory regulators dynorphin A and neuregulin-1 in the spinal cord is reduced. The puerperium did not alter spinal cord microgial and astrocyte activation. Astrocyte activation, as measured by glial fibrillary acidic protein (GFAP) expression, was not evident in female rats with injury, regardless of delivery status suggesting sex differences in spinal astrocyte activation after injury. These results suggest a change in the descending inhibitory/facilitating balance on spinal nociception neurotransmission during the puerperium, as mechanisms for its protective effect against injury-induced hypersensitivity.

Molecular characterization of the subnuclei in rat habenula

The mammalian habenula is involved in regulating the activities of serotonergic and dopaminergic neurons. It consists of the medial and lateral habenulae, with each subregion having distinct neural connectivity. Despite the functional significance, manipulating neural activity in a subset of habenular pathways remains difficult because of the poor availability of molecular markers that delineate the subnuclear structures. Thus, we examined the molecular nature of neurons in the habenular subnuclei by analyzing the gene expressions of neurotransmitter markers. The results showed that different subregions of the medial habenula (MHb) use different combinations of neurotransmitter systems and could be categorized as either exclusively glutamatergic (superior part of MHb), both substance P-ergic and glutamatergic (dorsal region of central part of MHb), or both cholinergic and glutamatergic (inferior part, ventral region of central part, and lateral part of MHb). The superior part of the MHb strongly expressed interleukin-18 and was innervated by noradrenergic fibers. In contrast, the inferior part, ventral region of the central part, and lateral part of the MHb were peculiar in that acetylcholine and glutamate were cotransmitted from the axonal terminals. In contrast, neurons in the lateral habenula (LHb) were almost uniformly glutamatergic. Finally, the expressions of Htr2c and Drd2 seemed complementary in the medial LHb division, whereas they coincided in the lateral division, suggesting that the medial and lateral divisions of LHb show strong heterogeneity with respect to monoamine receptor expression. These analyses clarify molecular differences between subnuclei in the mammalian habenula that support their respective functional implications.

Molecular characterization of the subnuclei in rat habenula

AbstractThe mammalian habenula is involved in regulating the activities of serotonergic and dopaminergic neurons. It consists of the medial and lateral habenulae, with each subregion having distinct neural connectivity. Despite the functional significance, manipulating neural activity in a subset of habenular pathways remains difficult because of the poor availability of molecular markers that delineate the subnuclear structures. Thus, we examined the molecular nature of neurons in the habenular subnuclei by analyzing the gene expressions of neurotransmitter markers. The results showed that different subregions of the medial habenula (MHb) use different combinations of neurotransmitter systems and could be categorized as either exclusively glutamatergic (superior part of MHb), both substance P‐ergic and glutamatergic (dorsal region of central part of MHb), or both cholinergic and glutamatergic (inferior part, ventral region of central part, and lateral part of MHb). The superior part of the MHb strongly expressed interleukin‐18 and was innervated by noradrenergic fibers. In contrast, the inferior part, ventral region of the central part, and lateral part of the MHb were peculiar in that acetylcholine and glutamate were cotransmitted from the axonal terminals. In contrast, neurons in the lateral habenula (LHb) were almost uniformly glutamatergic. Finally, the expressions of Htr2c and Drd2 seemed complementary in the medial LHb division, whereas they coincided in the lateral division, suggesting that the medial and lateral divisions of LHb show strong heterogeneity with respect to monoamine receptor expression. These analyses clarify molecular differences between subnuclei in the mammalian habenula that support their respective functional implications. J. Comp. Neurol. 520:4051–4066, 2012. © 2012 Wiley Periodicals, Inc.

Cutaneous innervation of the human face as assessed by skin biopsy

The morphology of cutaneous sensory and autonomic innervation in human trigeminal territory is still unknown. The aim of this study is to describe facial cutaneous innervation using skin biopsy. This new tool could be useful in understanding the mechanisms underlying several facial pain conditions. In 30 healthy subjects, we quantified epidermal nerve fibers (ENFs) and dermal myelinated fibers (MFs) in V1, V2 and V3, using indirect immunofluorescence and confocal microscopy applied to 2-mm punch skin biopsies from areas adjacent to the eyebrow, upper and lower lip. Using selective markers, we also evaluated the distribution of peptidergic, cholinergic and noradrenergic fibers. Facial skin appeared abundantly innervated and rich in annexes. The ENF density decreased and the MF density increased, moving from the supraorbital to the perioral skin. Noradrenergic sudomotor fibers were particularly and constantly expressed compared with other body sites. Distribution of vasoactive intestinal peptide-immunoreactive (VIP-ir) fibers appeared peculiar for their constant presence in the subepidermal neural plexus - in close contact, but without colocalization with calcitonin gene related peptide (CGRP) and substance P (Sub-P)-ir fibers. Finally, in perioral skin samples, we observed striated muscle fibers with their motor nerves and motor endplates. Our work provides the first morphological study of human facial cutaneous innervation, highlighting some unique features of this territory. Quantification of unmyelinated and myelinated fibers on 2-mm punch biopsies appeared to be feasible and reliable. Facial skin biopsy may be a new approach with which to study and to better characterize facial pain syndromes.