Innervation In Rats Research Articles

Oxytocin Attenuates Sympathetic Innervation with Inhibition of Cardiac Mast Cell Degranulation in Rats after Myocardial Infarction.

Sympathetic hyperinnervation is the leading cause of fatal ventricular arrhythmia (VA) after myocardial infarction (MI). Cardiac mast cells cause arrhythmias directly through degranulation. However, the role and mechanism of mast cell degranulation in sympathetic remodeling remain unknown. We investigated the role of oxytocin (OT) in stabilizing cardiac mast cells and improving sympathetic innervation in rats. MI was induced by coronary artery ligation. Western blotting, immunofluorescence, and toluidine staining of mast cells were performed to determine the expression and location of target protein. Mast cells accumulated significantly in peri-infarcted tissues and were present in a degranulated state. They expressed OT receptor (OTR), and OT infusion reduced the number of degranulated cardiac mast cells post-MI. Sympathetic hyperinnervation was attenuated as assessed by immunofluorescence for tyrosine hydroxylase (TH). Seven days post-MI, the arrhythmia score of programmed electrical stimulation was higher in vehicle-treated rats with MI than in rats treated with OT. An in vitro study showed that OT stabilized mast cells via the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Further in vivo studies on OTR-deficient mice showed worsening mast cell degranulation and worsening sympathetic innervation. OT pretreatment inhibited cardiac mast cell degranulation post-MI and prevented sympathetic hyperinnervation, along with mast cell stabilization via the PI3K/Akt pathway. SIGNIFICANCE STATEMENT: This is the first study to elucidate the role and mechanism of oxytocin (OT) in inflammatory-sympathetic communication mediated sympathetic hyperinnervation after myocardial infarction (MI), providing new approaches to prevent fatal arrhythmias.

Alpha-Lipoic Acid Ameliorates Radiation-Induced Salivary Gland Injury by Preserving Parasympathetic Innervation in Rats.

Radiation therapy is a standard treatment for patients with head and neck cancer. However, radiation exposure to the head and neck induces salivary gland (SG) dysfunction. Alpha lipoic acid (ALA) has been reported to reduce radiation-induced toxicity in normal tissues. In this study, we investigated the effect of ALA on radiation-induced SG dysfunction. Male Sprague–Dawley rats were assigned to the following treatment groups: control, ALA only (100 mg/kg, intraperitoneally), irradiation only, and ALA administration 24 h or 30 min prior to irradiation. The neck area, including SGs, was irradiated evenly at 2 Gy/min (total dose, 18 Gy) using a photon 6 MV linear accelerator. The rats were sacrificed at 2, 6, 8, and 12 weeks after irradiation. Radiation decreased SG weight, saliva secretion, AQP5 expression, parasympathetic innervation (GFRα2 and AchE expression), regeneration potentials (Shh and Ptch expression), salivary trophic factor levels (brain-derived neurotrophic factor and neurturin), and stem cell expression (Sca-1). These features were restored by treatment with ALA. This study demonstrated that ALA can rescue radiation-induced hyposalivation by preserving parasympathetic innervation and regenerative potentials.

Cannabinoid CB1 receptor inverse agonist MJ08 stimulates glucose production via hepatic sympathetic innervation in rats

As a key insulin target tissue for maintaining systemic glucose homeostasis, the liver plays important roles in improving obesity-associated insulin intolerance via selective cannabinoid CB1 receptor antagonism/inverse agonism. However, it is unclear whether this receptor inverse agonism affects hepatic glucose metabolism. MJ08 is a novel cannabinoid CB1 receptor antagonist/inverse agonist that has superior inverse agonism over the well-known antagonist/inverse agonist, SR141716 (rimonabant). MJ08 remarkably elevates fasting blood glucose independent of inhibition of insulin release in mice. In the current study, MJ08 was used to investigate the mechanism by which liver cannabinoid CB1 receptor inverse activation regulates hepatic glucose metabolism. MJ08 stimulated hepatic glucose production (HGP) in a dose-dependent manner and promoted gluconeogenic gene expression in perfused rat liver. SR141716 exhibited similar but weaker effects. The cannabinoid CB1 receptor agonist (WIN 55,212-2), Gs protein-cyclic AMP (cAMP)-dependent pathway inhibitors (NF449 and H89), β-adrenoceptor antagonist (propranolol), and peripheral sympathetic inhibitor (reserpine) could antagonize MJ08-induced HGP. Furthermore, MJ08 and SR141716 induced monoamine neurotransmitter (noradrenaline) release and increased cAMP content significantly in perfused liver, although only a slight increase was observed in primary cultured hepatocytes. These results indicate that local liver cannabinoid CB1 receptor inverse agonism via hepatic sympathetic innervation is responsible for the HGP induced by MJ08. Thus, high inverse agonistic activity could increase fasting blood glucose levels and should be avoided in the development of peripheral cannabinoid CB1 receptor-targeted weight-loss drugs.

Development of neuropeptide Y-mediated heart innervation in rats

Neuropeptide Y (NPY) plays a trophic role in the nervous and vascular systems and in cardiac hypertrophy. However, there is no report concerning the expression of NPY and its receptors in the heart during postnatal development. In the current study, immunohistochemistry and Western blot analysis was used to label NPY, and Y1R, Y2R, and Y5R receptors in the heart tissue and intramural cardiac ganglia from rats of different ages (newborn, 10days old, 20days old, 30days old, 60days old, 1year old, and 2years old).The obtained data suggest age-dependent changes of NPY-mediated heart innervation. The density of NPY-immunoreactive (IR) fibers was the least in newborn animals and increased in the first 20days of life. In the atria of newborn and 10-day-old rats, NPY-IR fibers were more abundant compared with the ventricles. The vast majority of NPY-IR fibers also contained tyrosine hydroxylase, a key enzyme in catecholamine synthesis.The expression of Y1R increased between 10 and 20days of life. Faint Y2R immunoreactivity was observed in the atria and ventricles of 20-day-old and older rats. In contrast, the highest level of the expression of Y5R was found in newborn pups comparing with more adult rats. All intramural ganglionic neurons were also Y1R-IR and Y5R-IR and Y2R-negative in all studied animals.Thus, the increasing of density of NPY-containing nerve fibers accompanies changes in relation of different subtypes of NPY receptors in the heart during development.

Hind Limb Sensory Innervation in Rats: Comparison between Sural and Saphenous Nerve Morphometry

Aunque numerosos estudios investigan la recuperacion sensorial del miembro pelvico o posterior de la rata despues del dano en los nervios, aun no existe en la literatura una vision global de su inervacion normal. Investigamos la morfometria de fibras mielinicas de los nervios sural y safeno y analizamos sus distribuciones de tamano en ratas jovenes. Seis ratas Wistar de 30 dias de edad fueron perfundidas con 2,5% de glutaraldehido, se prepararon los nervios sural y safeno derecho e izquierdo para microscopia de luz y morfometria. Datos morfometricos fueron comparados entre los segmentos (proximal vs distal) y laterales (derecho vs izquierdo) para los mismos nervios. Ademas, los segmentos de los lados derecho e izquierdo se compararon entre los nervios (sural vs safeno). Ambos nervios sural y safeno exhibieron una simetria proximal a distal en ambos lados, asi como una simetria izquierda-derecha. Histogramas del diametro de las fibras mielinizadas eran unimodales en ambos nervios, independientemente de los segmentos o de los lados, siendo los peaks del tamano de las fibras entre 2,5 y 4,0 micras. Las distribuciones de los axones reflejan las distribuciones de fibras mielinizadas, de los nervios sural y safeno que alcanzaban entre 1,5 and 2,0 µm. La relacion de G (relacion entre los diametros de los axones y de fibra) eran tambien unimodales, alcanzando 0,6 para ambos nervios. Este estudio contribuye a la literatura con los datos de la morfometria de fibras mielinizadas de ambos nervios sensoriales responsables de la inervacion de la extremidad pelvica de la rata. Esta informacion es valiosa para una mejor comprension de los nervios sural y safeno en la recuperacion sensorial del miembro despues de que uno de estos nervios ha sido danado.

Innervation of Rat and Human Dura Mater and Pericranial Tissues in the Parieto‐Temporal Region by Meningeal Afferents

To reinvestigate the innervation pattern of the dura mater of rat and human middle cranial fossa, the morpho-functional substrate of headache generation, and adjacent extracranial tissues with neuronal in vitro tracing. This study was initiated by recent structural and functional findings of meningeal afferent fibers which innervate the cranial dura mater and may project to extracranial tissues. Anterograde and retrograde neuronal in vitro tracing was made in formaldehyde fixed hemisected rat and human skulls. The fluorescent tracer DiI was applied to proximally cut meningeal nerves in rat and to distal branches of the spinosus nerve in human calvaria lined by dura mater. After several weeks, the dura mater and deep extracranial tissues were examined with fluorescence microscopy. In addition to a network of meningeal nerve fibers, several fiber bundles were observed, leaving the skull through emissary canals and fissures to innervate the pericranial temporal, parietal, and occipital periosteum. Traced fibers were seen spreading into deep layers of the temporal and upper neck muscles. Retrograde neuronal tracing revealed labeled cell bodies exclusively in the mandibular and maxillary division of the rat trigeminal ganglion, and centrally projecting fibers were identified in the spinal trigeminal tract. Electron microscopy of the cross-sected spinosus nerve showed myelinated and unmyelinated axons with similar numbers in human and rat. We conclude that a proportion of meningeal afferents innervates extracranial tissues like periosteum and pericranial muscles via collaterals projecting through the skull. These afferents may be nociceptive, some may subserve proprioceptive functions. The finding of extracranial projections of meningeal afferents may be important for our understanding of extracranial impacts on headache generation and therapy.

Innervation mapping of the hind paw of the rat using Evans Blue extravasation, Optical Surface Mapping and CASAM.

Although numerous studies investigate sensory regeneration and reinnervation of the hind paw of the rat after nerve damage, no comprehensive overview of its normal innervation is present in literature. The Evans Blue extravasation technique is a well-known technique to study patterns of skin innervation. This technique has been performed differently by various groups but was never used to study the entire skin innervation in rats' hind paw including all three branches of the sciatic nerve and the saphenous nerve in detail. In this paper, we have used the Evans Blue extravasation technique to chart the skin areas innervated by the sural, peroneal, tibial and/or saphenous nerves, which together innervate the entire hind paw of the rat, and use a new technique to analyze the distribution, overlap and variability of the results. The technique is based on analysis of whole hind paws using Optical Surface Mapping (OSM) in combination with the Computer Assisted Surgical Anatomy Mapping (CASAM) technology. While the plantar hind paw is mainly innervated by the tibial nerve, the dorsal hind paw is supplied by the sural, peroneal and the saphenous nerve. Although our results basically concur with the general nerve-specific innervation of the rat hind paw, they show considerable detail in their areas of overlap as well as in the amount of variability between animals. These results will be invaluable to study and evaluate patterns of innervation and reinnervation of intact and damaged nerve fibers.

Special AT-rich sequence-binding protein-2 (Satb2) — Independent initiation of cholinergic sweat gland innervation in rat in vivo

The transcription factor special AT-rich sequence-binding protein-2 (Satb2) is induced and critical for the establishment of the cholinergic phenotype in rat superior cervical ganglion cells in culture during switching from a noradrenergic to the cholinergic phenotype upon exposure to soluble differentiation factors. To obtain evidence for Satb2 determining the sympathetic cholinergic sudomotor phenotype also in vivo, we traced the postnatal expression profile of Satb2 in the rat stellate ganglion in comparison to the vesicular acetylcholine transporter (VAChT), choline acetyltransferase (ChAT), and the neuropeptide calcitonin gene-related peptide (CGRP), all required for sudomotor function in adult rats.

Controlled ingestion of kaolinite (5%) modulates enteric nitrergic innervation in rats

We have previously shown that kaolinite slowed down gastric emptying and intestinal transit and induced changes in enteric mechanical activities. As gastric emptying and intestinal transit have been shown to be regulated by nitric oxide (NO), the effect of an imposed ingestion of kaolinite on enteric nitrergic innervation was determined. Kaolinite has also been shown to increase plasmatic levels of leptin. Therefore, the responses of enteric neurons in the presence of leptin after kaolinite ingestion were determined, and a possible role of nitrergic neurons was evaluated in rats using organ bath technique. Our results showed that kaolinite modulates activities of enteric nerves at 14days of ingestion. Exogenous l-NNA produced a decrease in nerve stimulation (NS)-induced relaxation in both jejunum and colon of control groups. At 14days of kaolinite ingestion, this effect of l-NNA was significantly reduced only in the jejunum. Although l-NNA did not affect NS-induced contraction in jejunum and colon of control animals, it increased the amplitude of the NS-induced contraction in the colon of rats at 14days of kaolinite ingestion. Leptin inhibitory effects on ENS in the jejunum were also altered at 14days of ingestion. These differences were masked in the presence of l-NNA. Our data give evidence that changes in mechanical activities induced by kaolinite might be due to alterations in inhibitory (nitrergic and/or other) innervation at 14days of kaolinite ingestion and to modifications of leptin effects on the responses to intramural nerve stimulation.

Sympathetic renal nerve ultrastructure: Comparative analysis between adult mice and rats.

The renal nerves exhibit efferent and afferent sympathetic fibers, crucial for regulation of renal function and input of sensory information from the kidneys to the central nervous system. The intrinsic renal innervation was widely described in rats. However, few reports deal with renal extrinsic innervation in rats and mice, and comparative studies between species have not been reported. We aimed to compare the ultrastructural and morphometric characteristics of the extrinsic renal nerves of adult rats and mice. A total of 15 left renal nerves, 5 from adult male C57BL/6 mice and 10 from adult male Wistar rats were used. The renal nerves were dissected and prepared for light and electron microscopy morphometry. As expected, the difference of the fascicular area and diameter was significant, being the nerves of mice smaller than rats. The myelinated fibers of rats were larger (diameter and area) compared to mice, but the number and density of these fibers were not different between species. No morphological differences were observed (number, area, diameter, and size distribution) on the unmyelinated fibers between species. Our results indicate that fascicle and myelinated fibers sizes accompany the animal size. The unmyelinated fibers, mainly responsible for the sympathetic functions of the renal nerve, do not differ between species in size and number, suggesting the absence of functional differences.

Distribution and ultrastructural features of the serotonin innervation in rat and squirrel monkey subthalamic nucleus

The main purpose of this light and electron microscopic immunocytochemical study was to characterize and compare the serotonin (5-HT) innervation of the subthalamic nucleus (STN) in rats and squirrel monkeys (Saimiri sciureus) following labeling with an antibody against the 5-HT transporter (SERT). Unbiased counts of SERT+ axon varicosities revealed an average density of 5-HT innervation higher in monkeys (1.52 x 10(6) varicosities/mm3) than rats (1.17 x 10(6)), particularly in the anterior half of the nucleus (1.70 x 10(6)). As measured by electron microscopy, SERT+ axon varicosity profiles in the STN of both species were smaller than unlabeled profiles. The number of SERT+ profiles displaying a synaptic junction indicated that, in both rat and monkey STN, approximately half of 5-HT axon varicosities were asynaptic. In monkeys, all synaptic junctions made by SERT+ varicosities were asymmetrical, as opposed to only 77% in rats. Despite the higher density of 5-HT innervation in the anterior half of monkey STN, the ultrastructural features of its SERT+ varicosities, including synaptic incidence, did not significantly differ from those in its posterior half. These findings suggest that, throughout the rat and monkey STN, 5-HT afferents may exert their influence via both synaptic delivery and diffusion of 5-HT, and that an ambient level of 5-HT maintained in STN by these two modes of transmission might also modulate neuronal activity and influence motor behavior. A better understanding of the factors governing the complex interplay between these signaling processes would greatly improve our knowledge of the physiopathology of the STN.

Bronchopulmonary innervation defects in infants and rats with congenital diaphragmatic hernia

Introduction Pulmonary morbidity in survivors of congenital diaphragmatic hernia (CDH) is caused by hypoplasia, barotraumas, or other reasons. We have previously shown deficient tracheal innervation in rats with CDH. Now we examine whether bronchopulmonary innervation is also abnormal in both infants and rats with CDH. Material and Methods Sections of E15, E18, and E21 rat lungs were immunostained for Protein gene product 9.5 and S100 antibodies. Similar immunostaining was performed on tissue from infants dying from CDH (n = 6) and other causes (n = 6) with Neurofilament, S100, and Rearranged during transfection antibodies. Nerve trunks/bronchus were counted, and the proportion of glial and RET-positive cells/bronchial surface was calculated. Glial cell-line derived neurotrophic factor protein and mRNA were measured in rat lungs. Results Nerve trunks/bronchus were decreased in infants and rat fetuses with CDH. In contrast, glial and RET-positive cells/bronchial surface were increased in infants and rats with CDH. Both lungs were equally affected. GDNF protein was high, whereas GDNF mRNA was decreased in preterm animals with CDH. Conclusions The lungs of infants and rats with CDH have decreased neural components compensated by increased supporting glial cells and persistence high expression of RET and GDNF protein. Because bronchopulmonary innervation controls airway smooth muscle, vessels, and glandular secretions, it is tempting to hypothesize that these deficiencies might play a role in respiratory morbidity in CDH.

Tracheal innervation is abnormal in rats with experimental congenital diaphragmatic hernia

Background Tracheobronchial motility influences lung development. Lung hypoplasia and lung sequelae accompany congenital diaphragmatic hernia (CDH) in which the vagus nerves and esophageal innervation are abnormal. As the vagus supplies tracheal innervation, this study tested the hypothesis that it might also be abnormal in rats with CDH. Material and Methods Intrinsic ganglia were counted and measured in whole mount acetylcholinesterase-stained tracheas from CDH and control E21 fetal rats. The relative surfaces occupied by neural structures were measured in tracheal sections immunostained for p75 NTR and PGP 9.5. PGP 9.5 protein and mRNA expression were determined. Mann-Whitney tests were used for comparisons between groups using P < .05 as significant. Results p75 NTR staining showed the neural crest origin of tracheal innervation. Scarce neural structures and smaller ganglia were found in CDH fetuses. PGP 9.5 protein expression was decreased in CDH fetuses, whereas PGP 9.5 mRNA levels were increased in comparison with controls. Conclusions Decreased density of neural structures and size of intramural ganglia, reduced expression of neural tissue and PGP 9.5 protein, and increased levels of PGP 9.5 mRNA reveal deficient tracheal innervation in rats with CDH. If similar anomalies exist in the human condition, they could contribute to explaining the pathogenesis of lung hypoplasia and bronchopulmonary sequelae.

Abnormal development of tracheal innervation in rats with experimental diaphragmatic hernia

We previously demonstrated that tracheobronchial innervation, originated from the vagus nerve and hence of neural crest origin, is deficient in rats with experimental congenital diaphragmatic hernia (CDH). The present study examines the development of this innervation during fetal life in an attempt to understand the nature of these deficiencies. Pregnant rats were given either 100 mg nitrofen or vehicle on E 9.5. Embryos were recovered on E15 and E18. Control and nitrofen/CDH pups (n = 10 each) were studied on each of these days and compared with our previous results on E21. Whole mount preparations of tracheas stained for anti-protein gene product 9.5 (PGP 9.5) and smooth muscle contractile alpha-actin were examined under confocal microscopy for the morphology of intrinsic neural network. Sections of tracheas were immunostained with anti-low-affinity neurotrophin receptor (p75(NTR)), neural cell marker PGP 9.5, and anti-glial cell marker S100 antibodies. The proportions of sectional areas occupied by neural and glial structures were measured in the proximal and distal trachea. PGP 9.5 protein, and mRNA expressions were determined. Mann-Whitney tests with a threshold of significance of P < 0.05 were used for comparison. Positive staining for p75(NTR) confirmed the neural crest origin of tracheal neural cells. The neural network appeared less organized on E15, and it was less dense on E18 in nitrofen-exposed embryos than in controls. The proportions of section surface occupied by neural elements were similar in both groups on E15, but that of glial tissue was significantly increased in nitrofen-exposed embryos. On E18, the relative neural surface was significantly reduced in CDH embryos in contrast with increased glial tissue surface. On E21 the proportion of neural tissue was reduced only in the distal trachea. The expression of PGP 9.5 protein was decreased in CDH fetuses on E18 and E21. In contrast, PGP 9.5 mRNA levels were increased in CDH fetuses on E18 and E21. The development of intrinsic innervation of the trachea in rats with CDH is abnormal with reduction of neural tissue accompanied by increase of glial tissue that could represent a response to neural damage. The significance of increased PGP 9.5 mRNA levels is unclear.

Depletion of peptidergic innervation in the gastric mucosa of streptozotocin-induced diabetic rats

Autonomic neuropathy affecting the gastrointestinal system is a major presentation of diabetic neuropathy. Changes in the innervation of gastric mucosa or muscle layers can contribute to gastrointestinal symptoms. The present study investigated this issue by quantitatively analyzing the immunohistochemical patterns of the gastric innervation in rats with streptozotocin (STZ)-induced diabetes. In control rats, calcitonin gene-related peptide (CGRP) and substance P (SP) (+) nerve fibers appeared in the gastric mucosa and muscle layers. Double immunohistochemical staining showed that immunoreactivities for SP and CGRP were co-localized with a pan-neuronal marker protein gene product 9.5. Both SP (+) nerve fibers (p<0.001) and CGRP (+) nerve fibers (p<0.005) were decreased in the gastric mucosa within 4 weeks of diabetes; the reduction persisted throughout 24 weeks. Diabetic rats treated with insulin did not show decrease of SP or CGRP (+) fibers in the mucosa 4 weeks after STZ injection (p>0.05). There was no significant change in SP (+) nerve fibers (p>0.05) or CGRP (+) nerve fibers (p>0.05) of the gastric muscle layers. Reverse transcription-polymerase chain reaction (RT-PCR) showed that the expression levels of SP and CGRP mRNA in the thoracic dorsal root ganglia were similar between diabetic and control animals (p>0.05). Qualitative and quantitative ultrastructural examinations on the gastric mucosa documented unmyelinated nerve degeneration. These results suggest the existence of gastric sensory neuropathy in STZ-induced diabetes, and this pathology provides a foundation for understanding diabetic gastropathy.

(120) Physiological relevance of a rodent model of degenerative disc disease

The American Pain Society estimates that 45% of the U.S. population seeks medical help for chronic pain at some point in their lives. Those affected include the 15% of Americans with persistent back pain. There are many potential sources including degenerative disc disease (DDD), which is one of the primary causes of chronic low back pain (LBP). Natural age related degeneration of lumbar intervertebral discs (IVDs) is common, but abnormal degeneration can occur, often resulting in pain, instability, and biomechanical movement disadvantages. IVDs are articular joints between vertebra and they act to distribute loads placed on the spine through hydrostatic pressures. The disc is composed of the exterior annulus fibrosus surrounded by ligaments and the central nucleus pulposus. The presence of nerve fibres and nerve endings in the lumbar IVDs and in the adjacent longitudinal ligaments has been demonstrated by many authors. In healthy discs, innervation is mostly limited to the posterior and anterior longitudinal ligaments and the superficial layers of the annulus fibrosus. Human IVDs are supplied by a variety of nerve fiber types including C- and A-delta fibers (substance P and CGRP), A-beta fibers (myelin basic protein) and sympathetic fibers entering from the sympathetic nerve truck. Specialized sensory nerve endings have also been described (i.e. pacinian corpuscles and golgi tendon organs). The goal of this study is to assess if the rat is of potential use to develop a relevant, rodent model of DDD-related LBP. Lumbar IVD innervation will be assessed in rats by immunohistochemistry to examine total innervation and fiber type(s). Preliminary results suggest that IVD innervation in rat and human are similar. Supported by grants from the Canadian Institute for Health Research (LSS) and the American Pain Society (MM). The American Pain Society estimates that 45% of the U.S. population seeks medical help for chronic pain at some point in their lives. Those affected include the 15% of Americans with persistent back pain. There are many potential sources including degenerative disc disease (DDD), which is one of the primary causes of chronic low back pain (LBP). Natural age related degeneration of lumbar intervertebral discs (IVDs) is common, but abnormal degeneration can occur, often resulting in pain, instability, and biomechanical movement disadvantages. IVDs are articular joints between vertebra and they act to distribute loads placed on the spine through hydrostatic pressures. The disc is composed of the exterior annulus fibrosus surrounded by ligaments and the central nucleus pulposus. The presence of nerve fibres and nerve endings in the lumbar IVDs and in the adjacent longitudinal ligaments has been demonstrated by many authors. In healthy discs, innervation is mostly limited to the posterior and anterior longitudinal ligaments and the superficial layers of the annulus fibrosus. Human IVDs are supplied by a variety of nerve fiber types including C- and A-delta fibers (substance P and CGRP), A-beta fibers (myelin basic protein) and sympathetic fibers entering from the sympathetic nerve truck. Specialized sensory nerve endings have also been described (i.e. pacinian corpuscles and golgi tendon organs). The goal of this study is to assess if the rat is of potential use to develop a relevant, rodent model of DDD-related LBP. Lumbar IVD innervation will be assessed in rats by immunohistochemistry to examine total innervation and fiber type(s). Preliminary results suggest that IVD innervation in rat and human are similar. Supported by grants from the Canadian Institute for Health Research (LSS) and the American Pain Society (MM).

6‐Hydroxydopamine lesion in the ventral tegmental area fails to reduce extracellular dopamine in the cerebral cortex

Dopamine and noradrenaline are both involved in modulation of superior cognitive functions that are mainly dependent on frontal cortex activity. Experimental evidence points to parallel variations in extracellular concentrations of catecholamines in the cerebral cortex, which leads us to hypothesize their corelease from noradrenergic neurons. This study aimed to verify this hypothesis, by means of cerebral microdialysis following destruction of dopaminergic innervation in rats. The unilateral injury of dopaminergic neurons, by 6-hydroxydopamine injection in the ventral tegmental area, dramatically reduced the immunoreactivity for dopamine transporter in the cerebral hemisphere ipsilateral to the lesion. Tissue dopamine content in the ipsilateral nucleus accumbens and medial prefrontal and parietal cortex was also profoundly decreased, whereas noradrenaline was only slightly affected. Despite the lower tissue content in the denervated side, the extracellular dopamine level was not changed in the cortex, although it was markedly decreased in the nucleus accumbens ipsilateral to the lesion. The effect of drugs selective for D(2)-dopaminergic (haloperidol) or alpha(2)-noradrenergic (RS 79948) receptors was verified. Haloperidol failed to modify extracellular dopamine in either cortex but increased it in the nucleus accumbens, such an increase being greatly reduced in the denervated side. On the other hand, RS 79948 increased extracellular dopamine and DOPAC in all areas tested, the increases being of the same degree in both intact and lesioned sides. The results strongly support the hypothesis that the majority of extracellular dopamine in the cortex, unlike that in the nucleus accumbens, originates from noradrenergic terminals.

Evidence for parasympathetic innervation of white adipose tissue, clearing up some vagaries

to the editor: Recently, we reported that fat tissue receives not only sympathetic but also parasympathetic innervation ([5][1]). Using microsurgery, transneuronal retrograde tracing, and hyperinsulinemic euglycemic clamps, we demonstrated that parasympathetic innervation of fat tissue has an

Sympathetic sprouting and changes in nociceptive sensory innervation in the glabrous skin of the rat hind paw following partial peripheral nerve injury

Previous studies have suggested that sympathetic sprouting in the periphery may contribute to the development and persistence of sympathetically maintained pain in animal models of neuropathic pain. In the present study, we examined changes in the cutaneous innervation in rats with a chronic constriction injury to the sciatic nerve. At several periods postinjury, hind paw skin was harvested and processed by using a monoclonal antibody against dopamine-beta-hydroxylase to detect sympathetic fibers and a polyclonal antibody against calcitonin gene-related peptide to identify peptidergic sensory fibers. We observed migration and branching of sympathetic fibers into the upper dermis of the hind paw skin, where they were normally absent. This migration was first detected at 2 weeks, peaked at 4-6 weeks, and lasted for at least 20 weeks postlesion. At 8 weeks postlesion, there was a dramatic increase in the density of peptidergic fibers in the upper dermis. Quantification revealed that densities of peptidergic fibers 8 weeks postlesion were significantly above levels in sham animals. The ectopic sympathetic fibers did not innervate blood vessels but formed a novel association and wrapped around sprouted peptidergic nociceptive fibers. Our data show a long-term sympathetic and sensory innervation change in the rat hind paw skin after the chronic constriction injury. This novel fiber arrangement after nerve lesion may play an important role in the development and persistence of sympathetically maintained neuropathic pain after partial nerve lesions.

Absence of cholinergic sympathetic innervation from limb muscle vasculature in rats and mice

Although the existence of cholinergic sympathetic vasodilatory innervation in limb muscle vasculature is well established for some species, previous pharmacological studies have failed to reveal the presence of such innervation in rats. Recently, Schafer and colleagues [Schafer, M.K., Eiden, L.E., Weihe, E., 1998. Cholinergic neurons and terminal fields revealed by immunohistochemistry for the vesicular acetylcholine transporter. II. The peripheral nervous system. Neuroscience 84(2), 361–376] reported that vesicular acetylcholine transporter immunoreactivity (VAChT-IR), a marker for cholinergic terminals, is present in the innervation of the microvasculature of rat hindlimb skeletal muscle and concluded that rats possess cholinergic sympathetic innervation of limb muscle vasculature. Because of our interest in identifying targets of cholinergic sympathetic neurons, we have analyzed the transmitter properties of the innervation of muscle vessels in rat and mouse limbs. We found that the innervation of vasculature in muscle is noradrenergic, exhibiting robust catecholamine histofluorescence and immunoreactivity for tyrosine hydroxylase (TH) and the peptide transmitters, neuropeptide Y (NPY) and occasionally vasoactive intestinal peptide (VIP). In contrast, cholinergic phenotypic markers, VAChT-IR and acetylcholinesterase (AChE) activity, are absent. Neuron cell bodies in sympathetic ganglia, retrogradely labeled with injections of tracer into limb muscles, also lacked VAChT but contained TH-IR. The innervation of large extramuscular feed arteries in hindlimbs was also devoid of cholinergic markers, as were the cell bodies of sympathetic neurons innervating extramuscular femoral arteries. These results, like those of previous physiological studies, provide no evidence for the presence of cholinergic sympathetic innervation of muscle vasculature in rats or mice.