Identification and treatment of Strongyloides stercoralis infection in a Boston Terrier dog from south-eastern Australia

Strongyloides stercoralis, the causative agent of strongyloidiasis, is a potentially zoonotic intestinal nematode endemic to northern Australia. Strongyloidiasis is typically observed in immunocompromised hosts and is characterised by gastrointestinal signs, respiratory symptoms and a failure to thrive. In immunocompromised hosts, hyperinfection syndrome and disseminated infections can prove life-threatening. A 24-month-old Boston Terrier dog was referred for investigation of chronic small and large intestinal watery hematochezic diarrhoea, emaciation and hematemesis. Small intestinal histology identified a nematode despite consecutive negative faecal flotations. A real-time polymerase chain reaction and Baermann test subsequently confirmed infection with S. stercoralis. The dog had received an oral parasiticide comprising milbemycin oxime and afoxolaner every month for the 11 months prior to this diagnosis. Despite fenbendazole being reported as successful in the treatment of canine strongyloidiasis, a course of fenbendazole failed to clear the infection. Eradication of S. stercoralis infection was confirmed after the administration of off-label ivermectin fortnightly for 12 doses. Attention should be paid to this nematode as the failure of routine copromicroscopic methods to diagnose S. stercoralis infections can result in misdiagnosis, mistreatment and progression of the disease. Off-label ivermectin may be an alternative to fenbendazole for the treatment of Strongyloides spp. infection in dogs.

Extracellular signal-regulated kinase activation in the spinal cord contributes to visceral hypersensitivity induced by craniofacial injury followed by stress

BACKGROUND

We previously developed an animal model to examine mechanisms that underlie the emergence of visceral hypersensitivity modeling pain characteristics of temporomandibular disorder (TMD) patients with comorbid irritable bowel syndrome (IBS). In ovariectomized (OVx) rats with estradiol (E2) replacement, visceral hypersensitivity developed subsequent to masseter muscle inflammation followed by repeated forced swim (FS) stress. The purpose of this study was to investigate whether activation of extracellular signal-regulated kinase (ERK) in the spinal cord contributes to visceral hypersensitivity in this overlapping pain model.

METHODS

In OVx with E2 replacement rats masseter muscle inflammation was followed by 3 day FS (comorbid condition). Depression-like behaviors were assessed by sucrose preference and in the elevated plus maze, and visceral sensitivity was measured by the visceromotor response (VMR) to colorectal distention. The protein level of ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in the L6-S2 dorsal spinal cord was analyzed by western blot.

KEY RESULTS

FS stress decreased sucrose consumption in E2 replaced rats in sucrose preference test. The expression of p-ERK1/2 in the L6-S2 dorsal spinal cord increased significantly in E2 with comorbid rats. Intrathecal injection of mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor PD98059 blocked the visceral hypersensitivity induced by masseter muscle inflammation combined with FS stress.

CONCLUSIONS & INFERENCES

These data indicate that ERK1/2 activation contributes to the visceral hypersensitivity evoked by craniofacial inflammation pain combined with stress. The results may provide a new therapeutic avenue for alleviating overlapping pain conditions.

Estradiol modulates visceral hyperalgesia by increasing thoracolumbar spinal GluN2B subunit activity in female rats

BACKGROUND

We previously reported estrogen modulates spinal N-methyl-d-aspartate (NMDA) receptor processing of colorectal pain through changes in spinal GluN1 subunit phosphorylation/expression. The purpose of this study was to investigate whether spinal GluN2B containing NMDA receptors are involved in estrogen modulation of visceral pain processing.

METHODS

Behavioral, molecular, and immunocytochemical techniques were used to determine spinal GluN2B expression/phosphorylation and function 48 h following subcutaneous injection of estradiol (E2) or vehicle (safflower oil, Saff oil) in ovariectomized rats in the absence or presence of colonic inflammation induced by mustard oil.

KEY RESULTS

E2 increased the magnitude of the visceromotor response (VMR) to colorectal distention compared to Saff oil in non-inflamed rats. Intrathecal injection of the GluN2B subunit antagonist, Ro 25-6981, had no effect on the VMR in non-inflamed E2 or Saff oil rats. Colonic inflammation induced visceral hyperalgesia in E2, but not Saff oil rats. Visceral hyperalgesia in E2 rats was blocked by intrathecal GluN2B subunit selective antagonists. In inflamed rats, E2 increased GluN2B protein and gene expression in the thoracolumbar (TL), but not lumbosacral (LS), dorsal spinal cord. Immunocytochemical labeling showed a significant increase in GluN2B subunit in the superficial dorsal horn of E2 rats compared to Saff oil rats.

CONCLUSIONS & INFERENCES

These data support the hypothesis that estrogen increases spinal processing of colonic inflammation-induced visceral hyperalgesia by increasing NMDA receptor activity. Specifically, an increase in the activity of GluN2B containing NMDA receptors in the TL spinal cord by estrogen underlies visceral hypersensitivity in the presence of colonic inflammation.

Blastocystis subtypes in symptomatic and asymptomatic family members and pets and response to therapy

BACKGROUND

Blastocystis is a common, enteric parasite. The pathogenicity of the organism is uncertain, but subtypes (ST) 1 and 3 have been reported more likely to cause irritable bowel-like symptoms.

AIMS

We treated symptomatic patients positive for Blastocystis with conventional therapy and analysed 16 small-subunit (SSU) rDNA to assess clearance and carriage rates and ST prevalence of the parasite in the asymptomatic household members.

METHODS

In a longitudinal, prospective case study, 11 symptomatic patients positive for Blastocystis underwent outpatient clinical assessment to exclude other diagnoses before 14 days of either metronidazole 400 mg three times daily or trimethoprim/sulfamethoxazole 160/800 mg twice-daily therapy. Faecal specimens were collected from patients at baseline, day 15, 28 and 56 after therapy and from 17 family members and eight pets at day 15. Specimens were analysed using faecal smear, culture and polymerase chain reaction analysis of 16SSU rDNA.

RESULTS

No patient cleared the organism following therapy. ST 1 (45%), 3 (36%), 4 (36%) and 6 (9%) were found in the symptomatic Blastocystis patients, and ST identified before and after therapy were identical in each individual. All household contacts were positive for Blastocystis and 16/17 (94%) contacts showed identical Blastocystis ST to the symptomatic family member. All pets were positive for Blastocystis with polymerase chain reaction testing, 7/8 (88%) demonstrating ST concordance with the symptomatic Blastocystis patients.

CONCLUSIONS

Conventional therapy is ineffective for symptomatic Blastocystis infection. The high prevalence of Blastocystis infection within households suggested transmission between humans and their pets. Subtyping analysis of SSU rDNA alone in Blastocystis does not appear to predict pathogenicity.

Canine vector-borne disease pathogens in dogs from south-east Queensland and north-east Northern Territory

OBJECTIVES

To determine the prevalence of canine vector-borne diseases (CVBD: Babesia spp., Anaplasma spp., Ehrlichia spp., haemotropic mycoplasmas and Hepatozoon) in Australian dogs; namely, dogs from pounds in south-east Queensland and an indigenous Aboriginal community in the north-east of the Northern Territory.

DESIGN AND PROCEDURE

Blood samples were collected from 100 pound dogs and 130 Aboriginal community dogs and screened for the CVBD pathogens using polymerase chain reaction (PCR). All positive PCR products were sequenced for species confirmation.

RESULTS

In total, 3 pound dogs and 64 Aboriginal community dogs were infected with at least one CVBD pathogen. Overall, B. vogeli was detected in 13 dogs, A. platys in 49, M. haemocanis in 23, Candidatus Mycoplasma haematoparvum in 3 and C. M. haemobos in 1 dog. Co-infections were detected in 22 Aboriginal community dogs.

CONCLUSIONS

This study found B. vogeli, A. platys and haemotropic mycoplasma infections to be common in dogs in subtropical and tropical areas of Australia. This study also reports for the first time the prevalence and genetic characterisation of haemotropic mycoplasmas in dogs in Australia.

First report of a Trichinella papuae infection in a wild pig (Sus scrofa) from an Australian island in the Torres Strait region

Multiple Trichinella species are reported from the Australasian region although mainland Australia has never confirmed an indigenous case of Trichinella infection in humans or animals. Wildlife surveys in high-risk regions are essential to truly determine the presence or absence of Trichinella, but in mainland Australia are largely lacking. In this study, a survey was conducted in wild pigs from mainland Australia's Cape York Peninsula and Torres Strait region for the presence of Trichinella, given the proximity of a Trichinella papuae reservoir in nearby PNG. We report the detection of a Trichinella infection in a pig from an Australian island in the Torres Strait, a narrow waterway that separates the islands of New Guinea and continental Australia. The larvae were characterised as T. papuae (Kikori strain) by PCR and sequence analysis. No Trichinella parasites were found in any pigs from the Cape York Peninsula. These results highlight the link the Torres Strait may play in providing a passage for introduction of Trichinella parasites from the Australasian region to the Australian mainland.

Prevalence of Cysticercus bovis in Australian cattle

OBJECTIVE

The first national abattoir survey of Cysticercus bovis ('beef measles') in cattle was conducted in February 2008.

METHODS

During the data collection period, 493,316 cattle were subjected to standard postmortem procedures, including incision of the masseter and heart muscles. On-site veterinarians were asked to record the location of any C. bovis cysts, as well as the National Livestock Identification System ear tag numbers of infected animals. Veterinarians were asked to submit samples for laboratory confirmation by histology and polymerase chain reaction testing.

RESULTS

Of the 23 samples submitted, none was positive for C. bovis by either diagnostic method.

CONCLUSIONS

Occasional, isolated diagnoses of beef measles are still made in most states of Australia, but since the last regional surveys were conducted 30 years ago, when the estimated prevalence was 50 to 200 per 100,000 cattle slaughtered, the parasite has become extremely rare.

The visceromotor response to colorectal distention fluctuates with the estrous cycle in rats

The existence of a sex difference in several chronic pain syndromes and the fluctuation of symptoms during the menstrual cycle strongly suggest sex hormones are involved in pain processing. The mechanisms underlying these changes are not well understood. Using the colorectal distention model in the rat, we previously reported a sex difference in the response to distention [Ji Y, Murphy AZ, Traub RJ (2006) Sex differences in morphine induced analgesia of visceral pain are supraspinally and peripherally mediated. Am J Physiol Regul Integr Comp Physiol 291:R307-R314] and that ovariectomy decreased the responses to distention while estrogen replacement reversed the decrease [Ji Y, Murphy AZ, Traub RJ (2003) Estrogen modulates the visceromotor reflex and responses of spinal dorsal horn neurons to colorectal stimulation in the rat. J Neurosci 23:3908-3915], suggesting estrogen increases visceral nociception. In the present study we tested the hypothesis that the visceromotor response to colorectal distention fluctuates with the estrous cycle. Three measurements (vaginal smears, uterine tube weight and plasma estrogen concentration) were used to determine the estrous phase. Comparison of the visceromotor response threshold and magnitude was made between proestrus and metestrus/diestrus. Our experiment demonstrated that the distention threshold was significantly lower in proestrus (median: 15 mm Hg) as compared with metestrus/diestrus (median: 25 mm Hg); and the magnitude of the visceromotor response to graded intensities of colorectal distentions (20, 40, 60, 80 mm Hg) was significantly higher in proestrus. The results indicate that the visceromotor response fluctuates with estrous phase, providing evidence for endogenous estrogen modulation of visceral nociceptive processing that could contribute to sex differences.

Blastocystis: subtyping isolates using pyrosequencing technology

Blastocystis is a prevalent single-celled enteric parasite of unresolved clinical significance. Efforts based on molecular methodologies to establish whether pathogenicity is linked to specific isolates of the genetically diverse genus of Blastocystis have been scarce and so far yielded ambiguous results which can be difficult to interpret. To alleviate some of the problems related to unravelling the molecular epidemiology of Blastocystis infections we developed and evaluated a simple and high-throughput sequence analysis (SQA) pyrosequencing technique based on the detection of genotype-specific nucleotide polymorphisms in the 18S small subunit rRNA gene for a rapid and cost-effective post-PCR screening of Blastocystis genotypes. The method was effectively capable of genotyping 48/48 isolates positive by nested PCR in approximately one hour, and in 94% of the cases the isolate detected by PCR and pyrosequencing was also detected by one of two different PCR assays with subsequent dideoxy sequencing.

Direct characterization of Blastocystis from faeces by PCR and evidence of zoonotic potential

In vitro propagation followed by PCR, and a PCR-based method capable of the direct detection of Blastocystis in faeces were utilized to detect Blastocystis from various hosts in Australia, including primates and their handlers from the Perth Zoo. In addition, Blastocystis isolates from dogs and humans living in a localized endemic community in Thailand were also characterized genetically. PCR-based detection directly from faeces was shown to be more sensitive compared with in vitro culture for the detection of Blastocystis. Moreover, phylogenetic analysis of Blastocystis isolates amplified utilizing in vitro techniques prior to PCR revealed that this method favoured the preferential amplification of Blastocystis subtype 5 over subtype 1. This study is the first to provide molecular-based evidence supporting the zoonotic potential of Blastocystis in dogs, possums and primates in a natural setting.

A case of mistaken identity – reappraisal of the species of canid and felid hookworms (Ancylostoma) present in Australia and India

This study serves to clarify the current status of canid and felid Ancylostoma species present in Australia. The morphological identification of A. ceylanicum from cats for the first time in Townsville, Australia, appears to be in error, together with the genetic markers provided for the species. Morphological and genetic data presented herein provide strong evidence that the hookworms from cats in Towsville are not A. ceylanicum as previously identified (i.e. the first report of this species in Australia), but are A. braziliense. Therefore the subsequent genetic markers established for A. ceylanicum in subsequent molecular studies based on these Townsville specimens should also be attributed to A. braziliense. Based on this information, a study of canine hookworm species present in northern India is also in error and it is apparent that the hookworms found in this region are those of A. ceylanicum. The distribution of A. braziliense and A. ceylanicum in the Americas and Asia Pacific region is discussed together with the importance of combining parasite morphology with genetic data for parasite diagnosis in epidemiological studies.

The radiological properties of a novel lung tissue substitute

Lung phantoms have been manufactured using commercially available, polyurethane foam products. Some of these materials are no longer available; therefore, a new lung tissue substitute was developed. The elemental composition and radiological properties of the new lung tissue substitute are described in this paper. Because the lung tissue substitute will be used to manufacture phantom lungs that will be used to evaluate chest counting systems, it is necessary to know the radiological properties of the material. These properties must be compared with reference materials and materials that have been used for lung phantoms in the past. The radiological properties of interest include the electron density, mean excitation energy, electron stopping power and photon mass attenuation coefficients. In all these properties, the calculated values for the new lung tissue substitute closely matched the calculated values of ICRU Publication 44 lung tissue. Good agreement was also found when the new lung tissue substitute was compared with the Griffith lung tissue substitute described by the ICRU. The new material was determined to be an excellent lung tissue substitute.

Molecular epidemiology: A multidisciplinary approach to understanding parasitic zoonoses

Sound application of molecular epidemiological principles requires working knowledge of both molecular biological and epidemiological methods. Molecular tools have become an increasingly important part of studying the epidemiology of infectious agents. Molecular tools have allowed the aetiological agent within a population to be diagnosed with a greater degree of efficiency and accuracy than conventional diagnostic tools. They have increased the understanding of the pathogenicity, virulence, and host-parasite relationships of the aetiological agent, provided information on the genetic structure and taxonomy of the parasite and allowed the zoonotic potential of previously unidentified agents to be determined. This review describes the concept of epidemiology and proper study design, describes the array of currently available molecular biological tools and provides examples of studies that have integrated both disciplines to successfully unravel zoonotic relationships that would otherwise be impossible utilising conventional diagnostic tools. The current limitations of applying these tools, including cautions that need to be addressed during their application are also discussed.

Epidemiological and molecular evidence supports the zoonotic transmission of Giardia among humans and dogs living in the same community

Giardia duodenalis isolates recovered from humans and dogs living in the same locality in a remote tea-growing community of northeast India were characterized at 3 different loci; the SSU-rDNA, elongation factor 1-alpha (ef1-alpha) and triose phosphate isomerase (tpi) gene. Phylogenetic analysis of the SSU-rDNA and efl-alpha genes provided poor genetic resolution of the isolates within various assemblages, stressing the importance of using multiple loci when inferring genotypes to Giardia. Analysis of the tpi gene provided better genetic resolution and placed canine Giardia isolates within the genetic groupings of human isolates (Assemblages A and B). Further evidence for zoonotic transmission was supported by epidemiological data showing a highly significant association between the prevalence of Giardia in humans and presence of a Giardia-positive dog in the same household (odds ratio 3.01, 95% CI, 1.11, 8.39, P = 0.0000).

Colonization and risk factors for Brachyspira aalborgi and Brachyspira pilosicoli in humans and dogs on tea estates in Assam, India

The prevalence of colonization with the anaerobic intestinal spirochaetes Brachyspira aalborgi and Brachyspira pilosicoli was investigated in humans (n = 316) and dogs (n = 101) living on three tea estates in Assam, India. Colonization was detected using PCR on DNA from faeces. Nineteen (6%) human faecal samples contained B. aalborgi DNA, 80 (25.3%) contained B. pilosicoli DNA, and 10 (3.2%) contained DNA from both species. One canine sample contained DNA from B. pilosicoli. Significant factors for B. aalborgi colonization in logistic regression were: infection of family members with B. aalborgi (P < 0.001), being a resident of Balipara (P = 0.03), and use of water treatment (P = 0.03). For B. pilosicoli, significant factors were: other family members being positive for B. pilosicoli (P < 0.001), water obtained from a well (P = 0.006), water treatment (P = 0.03), and not having visited a doctor in the previous 12 months (P = 0.03).

Methodology for worker neutron exposure evaluation in the PDCF facility design

A project headed by Washington Group International is meant to design the Pit Disassembly and Conversion Facility (PDCF) to convert the plutonium pits from excessed nuclear weapons into plutonium oxide for ultimate disposition. Battelle staff are performing the shielding calculations that will determine appropriate shielding so that the facility workers will not exceed target exposure levels. The target exposure levels for workers in the facility are 5 mSv y(-1) for the whole body and 100 mSv y(-1) for the extremity, which presents a significant challenge to the designers of a facility that will process tons of radioactive material. The design effort depended on shielding calculations to determine appropriate thickness and composition for glove box walls, and concrete wall thicknesses for storage vaults. Pacific Northwest National Laboratory (PNNL) staff used ORIGEN-S and SOURCES to generate gamma and neutron source terms, and Monte Carlo (computer code for) neutron photon (transport) (MCNP-4C) to calculate the radiation transport in the facility. The shielding calculations were performed by a team of four scientists, so it was necessary to develop a consistent methodology. There was also a requirement for the study to be cost-effective, so efficient methods of evaluation were required. The calculations were subject to rigorous scrutiny by internal and external reviewers, so acceptability was a major feature of the methodology. Some of the issues addressed in the development of the methodology included selecting appropriate dose factors, developing a method for handling extremity doses, adopting an efficient method for evaluating effective dose equivalent in a non-uniform radiation field, modelling the reinforcing steel in concrete, and modularising the geometry descriptions for efficiency. The relative importance of the neutron dose equivalent compared with the gamma dose equivalent varied substantially depending on the specific shielding conditions and lessons were learned from this effect. This paper addresses these issues and the resulting methodology.

Humans, dogs and parasitic zoonoses--unravelling the relationships in a remote endemic community in northeast India using molecular tools

Canine parasitic zoonoses pose a continuing public health problem, especially in developing countries and communities that are socioeconomically disadvantaged. Our study combined the use of conventional and molecular epidemiological tools to determine the role of dogs in transmission of gastrointestinal (GI) parasites such as hookworms, Giardiaand Ascarisin a parasite endemic tea-growing community in northeast India. A highly sensitive and specific PCR-RFLP was developed to detect and differentiate the zoonotic species of canine hookworm eggs directly from faeces. This allowed epidemiological screening of canine hookworm species in this community to be conducted with ease and accuracy. Seventy two percent of dogs were found to harbour A. caninum, 60% A. braziliense and 37% harboured mixed infections with both hookworms. No A. ceylanicum was detected in the dog population. The zoonotic potential of canine Giardiawas also investigated by characterising Giardia duodenalisrecovered from humans and dogs living in the same locality and households, at three different loci. Phylogenetic and epidemiological analysis provided compelling evidence to support the zoonotic transmission of canine Giardia. Molecular tools were also used to identify the species of Ascarisegg present in over 30% of dog faecal samples. The results demonstrated the role of dogs as a significant disseminator and environmental contaminator of Ascaris lumbricoidesin communities where promiscuous defecation practices exist. Our study demonstrated the usefulness of combining conventional and molecular parasitological and epidemiological tools to help solve unresolved relationships with regards to parasitic zoonoses.

NMDA receptor antagonists attenuate noxious and nonnoxious colorectal distention-induced Fos expression in the spinal cord and the visceromotor reflex

In the present three-part study, the effects of intrathecally administered N-methyl-D-aspartate (NMDA) receptor antagonists on responses to noxious and innocuous colorectal distention (CRD) were examined. In the first part, a passive-avoidance paradigm was used to confirm that 80 mm Hg CRD is a noxious stimulus since it produced avoidance behavior. Acquisition of this behavior was blocked by the NMDA receptor antagonist D(-)-2-amino-5-phosphonopetanoic acid (APV, 60 nmol, intrathecal). In contrast, 20 mm Hg CRD is an innocuous stimulus since there was no difference in the behavior of these animals compared to nondistended controls. In the second part, the effects of the NMDA receptor antagonist dizocilpine maleate (MK-801, 0-100 nmol, intrathecal) on CRD-induced Fos expression in the lumbosacral spinal cord were examined. Noxious and innocuous CRD induced 98+/-4 and 50+/-2 Fos labeled cells per section per side of the spinal cord, respectively. MK-801 dose-dependently attenuated noxious CRD-induced Fos. Compared to saline, the peak attenuation was 55%. Innocuous CRD-induced Fos was attenuated by 36% following 100 nmol MK-801. In the third part, the effects of APV (0-240 nmol, intrathecal) on the visceromotor reflex were examined. APV dose-dependently attenuated the visceromotor reflex to graded intensities of CRD that went from the innocuous into the noxious range. In separate animals that only received innocuous stimulation, APV dose-dependently attenuated the visceromotor reflex. The magnitude of attenuation was similar for both stimulus paradigms. These data expand upon our previous dorsal horn neuronal recordings which showed that spinal NMDA receptors partially mediate the processing of both noxious and innocuous colorectal stimuli. They further underscore a difference from somatic tissue in the role of NMDA receptors in processing acute or transient visceral stimuli in the absence of tissue injury.

Current challenges in personal dosimetry at the US DOE Hanford site

An overview is presented of the dosimetry system, dose equivalent calculation methodology, and QA/QC practices used at the US Department of Energy Hanford site. It describes some of the problems encountered in accurately measuring dose equivalent quantities under a broad range of field conditions that do not necessarily correlate with laboratory calibration conditions and the approach taken to solve these problems. Personnel at Hanford are monitored with a combination of Harshaw model 8825 and 8816 thermoluminescence dosemeters and CR-39 etched track dosemeters. Extremities are monitored using the ICN MeasuRing loaded with a Harshaw XD740 chipstrate TLD. All dosemeters employ LiF:Mg,Ti elements that are read on-site with Harshaw model 8800 and 6600 TLD readers. CR-39 dosemeters are electrochemically etched in non-commercial etch chambers and counted with an automated track counting system developed by Pacific Northwest National Laboratory. Problems with over response of the 8825 with respect to Hp(0.07), under-response of the 8825 with respect to Hp(3), and over response of the 8825 with respect to Hp(10) in Hanford's 90Sr/90Y beta radiation fields are discussed. Approaches to measurement of the operational quantities for field conditions and algorithm solutions to the above problems are described. Methods used to calibrate the ring dosemeter for Hanford field conditions together with limitations of the ring dosemeter in measuring Hp(0.07) for extremities, particularly when covered with protective clothing, are also discussed.

Spinal NMDA receptors contribute to neuronal processing of acute noxious and nonnoxious colorectal stimulation in the rat

The present study investigated the role of NMDA receptors in the spinal processing of acute noxious and nonnoxious colorectal stimulation using extracellular single-unit recording in the rat. Fifty-three neurons in the L6-S2 dorsal horn of the spinal cord were studied. Neurons were identified using touch and light pinch of the ipsilateral perianal/scrotal area and colorectal distention (CRD). All neurons had excitatory responses to CRD. Thirty neurons were studied using a search stimulus of 80-mmHg CRD. The effects of a systemically administered N-methyl-D-aspartate (NMDA) receptor channel blocker, dizocilpine maleate (MK-801) (0.1, 0.5, 1.0, and 5.0 mg/kg), were tested on the CRD-evoked responses of 13 neurons. The lowest dose had no effect on the neuronal responses to CRD, while greater doses lowered the CRD-evoked responses at all distention pressures tested (20, 40, 60, and 80 mmHg). Similarly, spinal application of MK-801 (20, 50, 100, and 200 nmol) attenuated CRD-evoked activity (n = 9). In addition, a spinally administered competitive NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (APV) (30, 60, 120, and 240 nmol), dose-dependently attenuated the CRD-evoked response at all distention pressures (n = 5). Systemically administered APV did not affect neuronal responses to CRD (n = 3). Twenty-three neurons were studied in animals that never received distention pressures exceeding 30 mmHg; the search stimulus ranged between 20- and 30-mmHg CRD. These neurons were tested using 20-mmHg CRD. Systemically administered MK-801 facilitated the response to 20-mmHg CRD in three neurons and inhibited the response in five neurons, and the response of five neurons was not affected. Spinally administered MK-801 had no effect on neuronal responses to 20-mmHg CRD in six neurons. However, spinally administered APV dose-dependently decreased the response to 20-mmHg CRD in four neurons. These results are consistent with our previous observations that used Fos expression as the index, suggesting that spinal NMDA receptors contribute to processing of both noxious and nonnoxious CRD.

Distribution of natural thorium in the tissues of a whole body

The distribution of thorium in the tissues of a whole body donor to the United States Transuranium and Uranium Registries is described. This case, identified by the USTUR as Case 0212, had two documented intakes of plutonium and americium from occupational accidents while employed at Hanford but no known occupational exposure to thorium. Concentrations of 239+240Pu, 241Am, and 232Th in the tissues are compared and the distribution of these isotopes in this case is evaluated. The distribution data for 232Th are compared to those from previous studies of thorium in human tissues resulting from environmental exposure and to an individual exposed to Thorotrast (colloidal ThO2) in a medical diagnostic procedure. The 232Th distribution data from this work are also compared against ICRP 30 and ICRP 69 models for the behaviour of thorium in the human body.

Evidence for thoracolumbar spinal cord processing of inflammatory, but not acute colonic pain

The lower bowel is innervated by visceral afferents projecting to the lumbosacral and thoracolumbar spinal segments. The present study tested the hypothesis that sensory processing from the normal colon occurs in the lumbosacral spinal cord with little or no activity in the thoracolumbar segments. Following colonic inflammation, viscerosensory processing in the thoracolumbar spinal cord is recruited, contributing to visceral hyperalgesia. A baseline visceromotor reflex to colorectal distention recorded in intact rats was eliminated following bilateral L6-S3 dorsal rhizotomies. The visceromotor reflex recovered to 29% of baseline following colonic inflammation. These results suggest that visceral hyperalgesia and referred pain in patients with lower bowel disorders partly result from novel viscerosensory processing in the thoracolumbar spinal cord.

The NMDA receptor antagonist MK-801 attenuates c-Fos expression in the lumbosacral spinal cord following repetitive noxious and non-noxious colorectal distention

The effects of pretreatment with an NMDA receptor antagonist, MK-801, on c-Fos (Fos) expression in the lumbosacral spinal cord following repetitive, noxious (80 mmHg) or non-noxious (20 mmHg) colorectal distention (CRD) was examined immunocytochemically in awake and urethane anesthetized rats. In awake rats, noxious CRD induced Fos expression in the lumbosacral spinal cord. Pretreatment with MK-801 (0.1-1.0 mg/kg, i.p.) produced no change or an increase in noxious CRD induced-Fos expression and caused aversive side effects. In order to examine greater doses of MK-801, further experiments were performed in rats anesthetized with urethane. Both noxious and non-noxious CRD induced Fos in the lumbosacral spinal cord. Pretreatment with MK-801 (0.5, 1.0, 5.0 mg/kg, i.p.) dose-dependently attenuated noxious CRD-induced Fos by 20-40%. Five mg/kg MK-801 attenuated non-noxious CRD-induced Fos by 20%. Lesser doses did not significantly attenuate Fos expression. The laminar distribution of Fos following MK-801 pretreatment revealed a tendency towards the deeper laminae showing the greatest attenuation at the highest dose of MK-801. Protein plasma extravasation in the colon measured with Evan's blue dye showed no difference between rats without balloons, rats with balloons that were not distended and non-noxious CRD. There was significantly more extravasation following noxious CRD. Pretreatment with systemic MK-801 had no effect on plasma extravasation produced by noxious CRD. These data suggest that the induction of Fos in the lumbosacral spinal cord by noxious and non-noxious CRD is partially NMDA receptor mediated. However, NMDA receptor activation contributes significantly more to noxious than non-noxious CRD-induced Fos. Inflammation of the colon following noxious CRD likely contributes to sensitization of colonic afferents which may contribute to the increased NMDA receptor-mediated Fos following the noxious stimulus.

The peptide content of colonic afferents decreases following colonic inflammation

Peripheral injury produces long term changes in peptide content in dorsal root ganglion (DRG) cells that contribute to the inflammatory process in the periphery and neuronal plasticity in the spinal cord. We report here the proportion of colonic afferents labeled for calcitonin gene-related peptide (CGRP), substance P (SP) or somatostatin (Som) in the T13-L2 and L6-S2 DRG and changes in the percentage of SP or CGRP labeled afferents 6, 24, and 72 h following induction of experimental colitis. Following injection of fluorogold (FG) into the descending colon, significantly more FG labeled DRG cells were observed in the T13-L2 than L6-S2 DRG. In noninflamed rats, in both spinal regions, 60-70% of the colonic afferents that were labeled with FG were double labeled for SP. Similar results were obtained when double labeling for CGRP. Only 20-30% of the FG labeled afferents were double labeled for Som. Following experimental colitis induced by intracolonic zymosan, there was a significant decrease in the percentage of cells double labeled for SP in the T13-L2 and L6-S2 DRG at 6, 24, and 72 h. The percentage of CGRP double labeled cells was decreased in the T13-L2 DRG at all time points, but only at 24 h in the L6-S2 DRG. The cell bodies of CGRP labeled colonic afferents were significantly larger than SP or Som in control rats. Inflammation did not affect the mean size of the double labeled cells. These results suggest that colonic inflammation increases SP and CGRP release in the spinal cord and the colon that is manifest as a decrease in peptide content in the cell bodies of the colonic afferents during the first 72 h following injury.

Spinal modulation of the induction of central sensitization

Peripheral tissue injury results in a change in the excitability of spinal dorsal horn neurons, central sensitization, and the behavioral correlate, hyperalgesia. It is proposed here that a dynamic balance exists between excitatory and inhibitory synaptic input to the spinal dorsal horn that functions to prevent central sensitization following brief, mild, noxious stimulation. Following more severe stimulation and injury, there is a loss of these inhibitory mechanisms that allow central sensitization to proceed. Single-unit recordings were made from L4-L5 deep dorsal horn neurons (wide dynamic range and nociceptive specific) from barbiturate-anesthetized rats that were non-inflamed or had a carrageenan-inflamed hindpaw. Baseline test responses to mechanical stimuli were obtained and normalized to 100%. An electrical conditioning stimulus (1 Hz, 20 s, C-fiber strength) was applied to the tibial nerve or the neuronal receptive field. Five seconds later the test stimulus was repeated and the magnitude of response compared to baseline. During the conditioning stimulus, 46% of the neurons from non-inflamed and inflamed rats showed wind-up although the magnitude of wind-up was significantly greater for inflamed rats. The remaining neurons showed no change (36-46%) or wind-down (8-18%). Five seconds following the end of the conditioning stimulus 67% of the neurons from non-inflamed rats had attenuated responses to mechanical stimuli (36% of baseline). The remaining neurons were either unaffected (30%) or facilitated (3%). Following inflammation significantly fewer neurons (28%) had attenuated responses and the magnitude of attenuation was significantly less than in non-inflamed rats (54% of baseline). The responses of the remaining neurons were unaffected (54%) or facilitated (18%). During subsequent test stimuli, the responses of 30% of the neurons from non-inflamed rats were facilitated to 140% of baseline. The responses of 46% of neurons from inflamed rats were facilitated to 160% of baseline. In these neurons there was significantly less initial attenuation following inflammation compared to non-inflamed rats. The response of the neuron during the electrical conditioning had no effect upon the response following conditioning. The conditioning stimulus given transcutaneously within the receptive field produced qualitatively similar results to tibial nerve stimulation. In non-inflamed rats, when the conditioning/test-stimulus interval was increased from 5 s to 10-30 s, the responses of 20% of the neurons were attenuated (compared to 67%) and the mean magnitude of attenuation was 52% of baseline (compared to 36% of baseline). However, the responses of only 33% of the neurons were ultimately facilitated (compared to 30%). The present study documents a short period following a low-frequency C-fiber input in which the response to natural stimuli is suppressed. It is suggested that this attenuation, whether or not expressed, prevents a significant portion of deep dorsal horn neurons from becoming sensitized to C-fiber input. This functions to prevent central sensitization when the noxious stimulus does not produce inflammation and it is not beneficial to the animal to become hyperalgesic (i.e., to alter its behavior in order to protect an injured limb and reduce painful sensations). Following injury-producing tissue damage and inflammation the mechanisms that produce the attenuation are reduced, with a concomitant increase in excitation to electrical and natural stimuli, suggesting that the attenuation is inhibitory modulation of nociceptive input and injury results in a disinhibition producing an increase in excitability and central sensitization.

Differential c-fos expression in the nucleus of the solitary tract and spinal cord following noxious gastric distention in the rat

c-Fos has been used as a marker for activity in the spinal cord following noxious somatic or visceral stimulation. Although the viscera receive dual afferent innervation, distention of hollow organs (i.e. esophagus, stomach, descending colon and rectum) induces significantly more c-Fos in second order neurons in the nucleus of the solitary tract and lumbosacral spinal cord, which receive parasympathetic afferent input (vagus, pelvic nerves), than the thoracolumbar spinal cord, which receives sympathetic afferent input (splanchnic nerves). The purpose of this study was to determine the contribution of sympathetic and parasympathetic afferent input to c-Fos expression in the nucleus of the solitary tract and spinal cord, and the influence of supraspinal pathways on Fos induction in the thoracolumbar spinal cord. Noxious gastric distention to 80 mmHg (gastric distension/80) was produced by repetitive inflation of a chronically implanted gastric balloon. Gastric distension/80 induced c-Fos throughout the nucleus of the solitary tract, with the densest labeling observed within 300 microns of the rostral pole of the area postrema. This area was analysed quantitatively following several manipulations. Gastric distension/80 induced a mean of 724 c-Fos-immunoreactive nuclei per section. Following subdiaphragmatic vagotomy plus distention (vagotomy/80), the induction of c-Fos-immunoreactive nuclei was reduced to 293 per section, while spinal transection at T2 plus distention (spinal transection/80) induced a mean of 581 nuclei per nucleus of the solitary tract section. Gastric distension/80 and vagotomy/80 induced minimal c-Fos in the T8-T10 spinal cord (50 nuclei/section), but spinal transection/80 induced 200 nuclei per section. Repetitive bolus injections of norepinephrine produced transient pressor responses mimicking the pressor response produced by gastric distension/80. This manipulation induced minimal c-Fos in the nucleus of the solitary tract and none in the spinal cord. It is concluded that noxious visceral input via parasympathetic vagal afferents, and to a lesser extent sympathetic afferents and the spinosolitary tract, contribute to gastric distention-induced c-Fos in the nucleus of the solitary tract. The induction of c-Fos in the nucleus of the solitary tract is significantly greater than in the viscerotopic segments of the spinal cord, which is partially under tonic descending inhibition, but is not subject to modulation by vagal gastric afferents. Distention pressures produced by noxious gastric distention are much greater than those produced during feeding, suggesting that c-Fos induction in the nucleus of the solitary tract to noxious distention is not associated with physiological mechanisms of feeding and satiety. The large vagal nerve-mediated induction of c-Fos in the nucleus of the solitary tract following gastric distension suggests that parasympathetic afferents contribute to the processing of noxious visceral stimuli, perhaps by contributing to the affective-emotional component of visceral pain.

Noxious colorectal distention induced-c-Fos protein in limbic brain structures in the rat

Colorectal distention is a non-invasive stimulus used to study visceral pain processing in the nervous system. In this study, immunocytochemical labeling for the immediate-early gene, c-Fos, was used to map limbic brain structures involved in processing visceral pain. Rats received noxious colorectal distention while loosely restrained or loose restraint without distention (control). The brains were immunostained and the density of Fos-labeled nuclei within areas of the brain associated with limbic function were examined. Many cortical (cingulate; retrosplenial; insular; perirhinal, entorhinal) and subcortical (periaqueductal gray; locus coeruleus; lateral parabrachial area; paraventricular, anterodorsal and centromedian thalamic nuclei; lateral septal area; dorsomedial hypothalamus; cortical amygdala; subiculum) areas were labeled in the control rats, but significantly more Fos was observed in these areas following noxious colorectal distention (CRD). Additional areas were labeled following CRD but not restraint (e.g. infralimbic and prelimbic cortices; mediodorsal thalamic nucleus; central amygdaloid nucleus). The results show that noxious visceral stimuli result in Fos expression in limbic structures that exceeds that induced by restraint stress, suggesting that different pathways and circuits are recruited by stimuli which can produce similar emotional responses.

Anti-somatostatin antisera, but neither a somatostatin agonist (octreotide) nor antagonist (CYCAM), attenuates hyperalgesia in the rat

Somatostatin has been reported to have both nociceptive and antinociceptive roles in sensory transmission in the spinal cord. In this study, antisera against SOM (alpha-SOM), a somatostatin antagonist (CYCAM) and a somatostatin agonist (octreotide), were evaluated for their role in thermal and mechanical hyperalgesia in a model of carrageenan-induced inflammatory pain in the rat. Intrathecal administration of alpha-SOM prior to hindpaw inflammation dose-dependently attenuated thermal and mechanical hyperalgesia and the increase in paw size for up to 4 h following injury. Administration of alpha-SOM 3 h following injury had no effect. Intrathecal administration of octreotide or CYCAM prior to or following injection of carrageenan had no effect on any measure. It is suggested that the lack of effect of octreotide and CYCAM resulted from low affinity for the SOM receptor subtypes in the rat spinal cord. The attenuation of hyperalgesia and paw size produced by alpha-SOM may have resulted from attenuation of somatostatin's role in producing a dorsal root reflex that modulates the increase in paw size following injury.

Attenuation of c-Fos expression in the rat lumbosacral spinal cord by morphine or tramadol following noxious colorectal distention

We have previously reported that repetitive, noxious colorectal distention (CRD) induces c-Fos in the lumbosacral spinal cord. This study examined the effects of the analgesics morphine and tramadol on c-Fos expression resulting from noxious CRD in the rat. Pre-treatment (30 min or 1 min, i.v.) with morphine (1.25 mg/kg-5.0 mg/kg) or tramadol (1 mg/kg-20 mg/kg) dose-dependently attenuated c-Fos expression to CRD in all areas of the L6-S1 spinal gray matter. The highest dose of morphine was equipotent to the highest dose of tramadol. Repetitive dosing (1/4 of the greatest dose every 30 min) was as effective as a single bolus dose for both drugs. The visceromotor response to CRD was dose-dependently attenuated by tramadol and was reversed by naloxone. However, the dose of tramadol that eliminated the visceromotor response (7% of control) reduced the c-Fos expression to 47% of control. These results demonstrate that these two analgesics attenuate immediate-early gene expression and the visceromotor response to a noxious visceral stimulus and suggest that complete attenuation of c-Fos expression is not necessary for these compounds to produce analgesia to a noxious visceral stimulus.

Spinal cord NADPH-diaphorase histochemical staining but not nitric oxide synthase immunoreactivity increases following carrageenan-produced hindpaw inflammation in the rat

Recent reports suggest that NADPH-diaphorase (NADPH-d) may be a histochemical marker for neuronal nitric oxide synthase (nNOS) in the central nervous system. Carrageenan-produced unilateral hindpaw inflammation in the rat results in a bilateral increase in NADPH-d in spinal cord neurons. This suggests there would be a bilateral increase in NO, which mediates thermal hyperalgesia. However, carrageenan-produced unilateral hindpaw inflammation results in hyperalgesia of the inflamed hindpaw only. This study determined (1) if neurons that labeled for NADPH-d following carrageenan-produced unilateral hindpaw inflammation colocalized nNOS, and (2) whether there was an increase in nNOS-ir neurons following inflammation. Following unilateral hindpaw inflammation, double labeling of tissue sections and single labeling of alternate serial sections revealed a lack of colocalization or mismatch between NADPH-d histochemical activity and nNOS-like immunoreactivity in neurons in lamina I, the dorsolateral funiculus and lamina X. Quantitative analysis showed no difference in the number of nNOS-ir neurons and NADPH-d labeled neurons in the superficial laminae of the spinal cord in non-inflamed animals. Following unilateral hindpaw inflammation, there was a 34% increase in the number of NADPH-d labeled neurons but no increase in the number of nNOS-ir neurons. These results indicate that nNOS-immunoreactive neurons and NADPH-diaphorase stained neurons are not identical and that nNOS does not increase as a result of hindpaw inflammation, leaving the source of NO involved in thermal hyperalgesia following injury in question.

Noxious distention of viscera results in differential c-Fos expression in second order sensory neurons receiving 'sympathetic' or 'parasympathetic' input

Visceral organs receive dual innervation from primary afferents commonly referred to as 'sympathetic' and 'parasympathetic' afferents. We have previously reported a significantly greater induction of immediate-early genes in the viscerotopically appropriate spinal cord segments receiving 'parasympathetic' afferent innervation (pelvic nerve) compared with those receiving 'sympathetic' afferent innervation (hypogastric nerve) following noxious colorectal distention. In this study, the nucleus of the solitary tract (NTS) and viscerotopically appropriate spinal cord segments were labeled immunocytochemically for c-Fos following noxious gastric or esophageal distention to determine if the differential labeling following 'sympathetic' (spinal) and 'parasympathetic' (vagal) visceral afferent input is a general phenomenon of the gastrointestinal tract. Gastric distention and esophageal distention induced considerable c-Fos in the NTS and virtually none in the thoracic spinal segments. These data suggest that 'parasympathetic' visceral afferents may be different than 'sympathetic' visceral afferents with respect to their ability to induce c-Fos following noxious visceral distention.

Experimental lumbar radiculopathy. Immunohistochemical and quantitative demonstrations of pain induced by lumbar nerve root irritation of the rat

OBJECTIVE

A series of experiments were designed to develop and validate an animal model of lumbar radiculopathy. More specifically, these investigations introduced a model of chronic neuropathic pain in the rat associated with clinically relevant lumbar nerve root trauma and evaluated the ability of the model to effect symptoms and begin to understand the underlying neurochemical and neurophysiologic factors associated with these neurologic abnormalities.

SUMMARY OF BACKGROUND DATA

A search of the literature suggested that these studies were a first attempt to distinguish and elucidate an experimental lumbar radiculopathy.

METHODS

Two basic approaches to nerve trauma were considered, direct damage to the nerve via compression, and introduction of foreign materials in proximity to the nerve root that might cause irritation and inflammation leading to chronic symptoms. Ligature around the nerve (i.e., surrounding the nerve with a suture) was considered a plausible irritant that might behave in an animal model in a similar way that nerve root entrapment, often observed in HNP and stenosis cases, might function in humans. Further, varying levels of irritation was modeled by using 4-0 silk as a mild and 4-0 chromic gut as a more harsh irritant.

STUDY DESIGN

Five distinct treatments of the nerve roots were investigated initially: 1) a sham intervention, where the surgery simply exposed the nerve roots and dorsal root ganglion followed by standard closing procedures; 2) nerve root clipping, where the nerve roots were clipped with a microhemoclip; 3) 4-0 silk ligature, where two loose ligatures of 4-0 silk were placed around the nerve roots; 4) 4-0 chromic gut 1, where one loose ligature of 4-0 chromic gut was placed around the nerve roots; and 5) 4-0 chromic gut 2, where four 0.3 cm pieces of 4-0 chromic gut were laid adjacent to the nerve roots and secured by two loose ligatures of 4-0 chromic gut. ANOVA techniques were used to test for differential effects across time for the five treatment groups in terms of animal function and biochemistry in the DRG.

RESULTS

Rats treated with chromic gut ligature in large quantity demonstrated differential patterns of results on the injured and noninjured sides consistent with a lumbar radiculopathy. The injured side demonstrated significantly worse thermal hyperalgesia related to neuropathic pain (P < 0.0001); initial mechanical hypoalgesia (P < .001), and motor dysfunction (P < .001) resolving within 2 weeks; significantly increased c-fos counts (P < .0001) 2 weeks postoperatively, which showed a consistent trend toward baseline and return to baseline by 12 weeks; significantly greater and highly increased VIP concentrations in the dorsal root ganglia 2 weeks postoperatively (P < .0001) that did not resolve or tend towards baseline after 12 weeks of follow-up in conjunction with a trend toward VIP depletion in the spinal cord 2 weeks postoperatively that did resolve to baseline until a 12-week concentration indicated a significant increase in concentration (P < .002). Quantitative and qualitative changes in c-fos and VIP, correlated with the patterns of behavior and function. Thus, for the first time, evidence to link outcome behaviors and function with underlying neurochemical processes is suggested.

CONCLUSIONS

When the same apparent conditions can be demonstrated in some situations to be causing pain and in other situations to be independent of pain, some additional factor or factors not considered in the original investigations may be mediating the outcome. Neurochemical consequences of nerve root irritation provide a theoretical framework for hypothesizing about various types of mediating events that might explain how similar apparent pathology might reasonably lead to different predictions about behavior consequences of the pathology.(ABSTRACT TRUNCATED AT 400 WORDS)

NADPH-diaphorase histochemistry provides evidence for a bilateral, somatotopically inappropriate response to unilateral hindpaw inflammation in the rat

Unilateral hindpaw inflammation produces several neurochemical changes in the ipsilateral spinal dorsal horn that have been interpreted as contributing to the associated hyperalgesia. NADPH-diaphorase histochemical staining was used to examine the response of a population of neurons 1, 2, 6 or 24 h following injection of 6 mg carrageenan into the left hindpaw of the rat. The resulting unilateral hindpaw inflammation produced a bilateral, time-dependent, reversible increase in the number of NADPH-diaphorase stained neurons in the lumbar spinal cord that peaked at 6 h. In laminae I-III, there was a significant increase in the number of NADPH-diaphorase stained neurons both ipsilateral (25.9 +/- 2.3) and contralateral (26.3 +/- 1.3) to the inflamed hindpaw relative to uninflamed, control animals (18.6 +/- 1.7, 17.4 +/- 1.7, respectively). A smaller but significant increase was observed in laminae IV-VII and X. Under dark field illumination, an increase in the number of densely stained neurons in laminae I-III was also observed to peak at 6 h. A greater percentage of the neurons observed under bright field illumination were visible under dark field illumination at 6 h (47%) compared to control (18%), suggesting an increase in the enzymatic activity of neurons in laminae I-III in addition to the increase in the number of neurons with threshold levels of NADPH-diaphorase activity. There was no consistent increase in this ratio over time in laminae IV-VII or X. Six hours following carrageenan, there was a bilateral 50% increase in the density of NADPH-diaphorase staining in the neuropil in the medial laminae I-III. Both spinal neurons and primary afferent axons contributed to this bilateral increase in staining as the number of NADPH-diaphorase stained dorsal root ganglion cell bodies increased 47% over control. In addition to the increase in staining in the lumbar spinal cord, at 6 h post carrageenan, there was a bilateral 23% increase over control in the number of stained neurons in the cervical dorsal spinal cord. For comparative purposes, the distribution of Fos-immunoreactive nuclei was compared to NADPH-diaphorase 6 h post carrageenan. The distribution of Fos-immunoreactive nuclei differed from the NADPH-diaphorase stained neurons, suggesting that two separate populations of neurons were stained. Unilateral hindpaw inflammation did not result in an increase in NADPH-diaphorase activity in the periaqueductal gray or the ventroposteriolateral thalamic nucleus. The relationship of NADPH-diaphorase to nitric oxide is discussed and it is concluded that NADPH-diaphorase,(ABSTRACT TRUNCATED AT 400 WORDS)

The role of nitric oxide in the development and maintenance of the hyperalgesia produced by intraplantar injection of carrageenan in the rat

Activation of the N-methyl-D-aspartate (NMDA) receptor has been reported to be involved in the mechanisms that underlie thermal hyperalgesia produced by the intraplantar injection of carrageenan. As NMDA-mediated thermal hyperalgesia produced in models of acute and persistent pain have been reported to involve production of nitric oxide, we examined the role of nitric oxide in both the development and maintenance of the thermal hyperalgesia produced by the intraplantar injection of carrageenan. In addition, we examined the role of nitric oxide in the maintenance of the mechanical hyperalgesia produced by intraplantar injection of carrageenan. Prior to the intraplantar injection of carrageenan (2 mg in 100 microliters) there was no significant difference in thermal withdrawal latencies or mechanical withdrawal thresholds between the left and right hindpaws. Three hours after injection of carrageenan into the left hindpaw, rats showed evidence of a significantly faster thermal withdrawal latency and lower mechanical withdrawal threshold of the left hindpaw compared to the right hindpaw. In addition, the left hindpaw was significantly increased in size (diameter) compared with the right hindpaw. In these same rats, the intrathecal administration of saline, NG-nitro-L-arginine methyl ester (L-NAME; 2-200 nmol) or the inactive enantiomer, NG-nitro-D-arginine methyl ester (D-NAME; 200 nmol) did not produce any significant change in thermal nociceptive withdrawal latencies in the non-injected paw. However, administration of L-NAME (2-20 nmol), but not saline or D-NAME produced a dose dependent and reversible block of the thermal hyperalgesia for a period of up to 3 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential expression of c-fos and c-jun in two regions of the rat spinal cord following noxious colorectal distention

Thoracolumbar and lumbosacral spinal segments that receive afferent input from the descending colon and rectum were stained immunocytochemically for c-Fos- and c-Jun-like proteins following repetitive, noxious colorectal distention (CRD). Noxious CRD (80 mmHg) resulted in significantly more c-Fos- and c-Jun-like immunoreactivity in the sacral dorsal horn than in the thoracic dorsal horn. In both regions of the spinal cord the increase in c-Fos-like immunoreactivity was at least twice that of c-Jun-like immunoreactivity. Basal levels of c-Jun but not c-Fos were observed in the thoracic intermediolateral nucleus (IML) and the sacral parasympathetic nucleus (SPN). Noxious CRD induced both c-Fos and c-Jun in the SPN, but not the IML.

Unilateral hindpaw inflammation produces a bilateral increase in NADPH-diaphorase histochemical staining in the rat lumbar spinal cord

Tissue injury results in several changes in spinal cord neurons that contribute to hyperalgesia arising from the injured tissue. In models of unilateral hindpaw inflammation, changes in the neurochemistry and electrophysiology of dorsal horn neurons ipsilateral, and to a much lesser extent contralateral, to the inflamed paw have been reported. For example, the excitability of dorsal horn neurons increases, receptive field size increases, and the content of various proteins and neuropeptides in the dorsal horn (e.g. FOS, dynorphin, enkephalin) are affected following peripheral inflammatory insult. These changes are typically interpreted on the basis of their relevance to nociception.

Analysis of calcitonin gene-related peptide-like immunoreactivity in the cat dorsal spinal cord and dorsal root ganglia provide evidence for a multisegmental projection of nociceptive C-fiber primary afferents

Recent studies have suggested that calcitonin gene-related peptide (CGRP) can be used as a marker for a subpopulation of nociceptive primary afferents. Consequently, CGRP-immunoreactive (CGRP-IR) primary afferents have been reported to project many segments rostral to their segment of entry and to send collaterals into the superficial and deep laminae of the dorsal horn. This study reports that some CGRP-IR primary afferents of sacral origin project rostral through the ipsilateral lumbar enlargement in the cat. The ultrastructure of these multisegmentally projecting primary afferent axons and terminals identified in a partially denervated cat was examined and compared to the ultrastructure of CGRP-IR afferents from an intact cat. Retrograde transport of wheatgerm agglutinin-colloidal gold injected into the cat L4 spinal cord resulted in labeling of primary afferent cell bodies in the ipsilateral L4-S1 dorsal root ganglia (DRG). Analysis of every fourth section through the ipsilateral S1 DRG revealed as many as 1,000 retrogradely labeled neuronal cell bodies. One third of these cell bodies were double labeled for CGRP-like immunoreactivity. The number of single- and double-labeled cells increased in ganglia closer to the injection site (L4-L7). At the ultrastructural level, in the lumbosacral dorsal spinal cord of a normal cat, most CGRP-IR axons were unmyelinated, while the rest were small myelinated axons. In both the superficial dorsal horn and lamina V, CGRP-IR varicosities were dome shaped, scallop shaped, or elongated. The CGRP-IR varicosities contained small agranular vesicles and frequently a few dense core vesicles. These labeled varicosities formed asymmetric synapses on unlabeled dendritic spines, shafts, or neuronal somata. One cat received multiple unilateral dorsal rhizotomies (S1-L4) and an ipsilateral hemisection (mid L4). CGRP-IR axons and terminals were found within each of the rhizotomized segments, although their density was greatly reduced compared to that in the intact animals. In Lissauer's tract the majority (greater than 90%) of CGRP-IR fibers were unmyelinated. In laminae I and V, the remaining CGRP-IR varicosities were mainly the dome-shaped varicosities morphologically similar to those observed in the normal spinal cords. They contained small agranular vesicles and a few dense core vesicles and formed asymmetric synapses on unlabeled dendritic shafts and spines. These data demonstrate that unmyelinated, presumably C-fiber nociceptive primary afferents and some small myelinated A-delta nociceptive primary afferents of sacral origin project rostral through the cat lumbar enlargement and make synaptic connections in both the superficial and deep laminae of the cat dorsal spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural demonstration of synaptic connections between calcitonin gene-related peptide immunoreactive axons and dynorphin A(1-8) immunoreactive dorsal horn neurons in a rat model of peripheral inflammation and hyperalgesia

Synaptic contact between dynorphin A(1-8)-like immunoreactive lamina V spinal neurons and calcitonin gene-related peptide-like immunoreactive axon terminals was demonstrated using the immuno-electron microscopic mirror technique in a rat model of peripheral inflammation and hyperalgesia. Adjacent tissue sections were immunocytochemically labeled for either dynorphin A(1-8) or calcitonin gene-related peptide and examined at the electron microscopic level for the presence of synaptic contacts. The results suggest that some opioid neurons which exhibit a dynamic increase in dynorphin peptide associated with peripheral inflammation and hyperalgesia receive direct monosynaptic input from presumptive nociceptive primary afferents.

Calcitonin gene-related peptide immunoreactivity in the cat lumbosacral spinal cord and the effects of multiple dorsal rhizotomies

This study determined the extent of the rostral projection of calcitonin gene-related peptide-like immunoreactive (CGRP-IR) primary afferents in the cat lumbosacral spinal cord. To do this we examined the distribution of CGRP-like immunoreactivity (CGRP-LI) contralateral and ipsilateral to multiple dorsal rhizotomies. In the contralateral dorsal spinal cord, CGRP-IR fibers were mostly observed in Lissauer's tract, the dorsal columns, and laminae I, II, and V. Fewer CGRP-IR fibers were observed in laminae III, IV, and VI and the area around the central canal. The location of the CGRP-LI suggests that the afferents arose from nociceptors. Unilateral dorsal rhizotomies of five consecutive segments in the lumbar enlargement caused a substantial although incomplete loss of CGRP-LI in the rhizotomized dorsal spinal cord ipsilateral to the lesions. The majority of the remaining CGRP-IR fibers were located in Lissauer's tract, the dorsal columns, and the lateral part of laminae I and V. Ventral rhizotomies or an ipsilateral hemisection in the most rostral rhizotomized segment, in addition to the dorsal rhizotomies, had no noticeable effect upon the density or location of the remaining CGRP-LI. These results suggest that the majority of the CGRP-LI within the rhizotomized region of spinal cord was contained within branches of small-diameter primary afferents that entered the spinal cord through intact dorsal roots located caudal to the rhizotomized segments of spinal cord. It is concluded that CGRP-IR small-diameter primary afferents are capable of projecting at least five segments beyond their segment of entry and supplying collaterals to the superficial and deeper layers of the dorsal horn involved in the processing of nociceptive information.

Effect of multiple dorsal rhizotomies on calcitonin gene-related peptide-like immunoreactivity in the lumbosacral dorsal spinal cord of the cat: a radioimmunoassay analysis

Calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was measured by radioimmunoassay in the cat lumbosacral dorsal spinal cord following unilateral dorsal rhizotomy of 5 consecutive dorsal roots. The dorsal rhizotomies greatly reduced but did not eliminate the CGRP-LI from the ipsilateral rhizotomized segments. The amount of CGRP-LI remaining in the rhizotomized segments was greatest in the most caudal segment (846 +/- 311 pmoles/g tissue) and decreased below 300 pmoles/g tissue in the remaining segments. When these values were compared to the intact contralateral side, the percent CGRP remaining ranged from 65% in the sacral segments to less than 20% in the lumbar segments. Rostral to the rhizotomized segments there was a gradual return of CGRP-LI to control levels within 3 segments. Small diameter primary afferent fibers are the only known source of CGRP within the dorsal spinal cord. These results suggest that the most likely origin of the CGRP that remained in the rhizotomized lumbar segments was the rostrally and caudally projecting branches of ipsilateral primary afferents that entered the spinal cord through intact dorsal roots caudal and rostral to the transected roots. These results support the hypothesis that small diameter primary afferents project several segments in the cat spinal cord.

Demonstration of calcitonin gene-related peptide immunoreactive axons contacting dynorphin A(1-8) immunoreactive spinal neurons in a rat model of peripheral inflammation and hyperalgesia

In a rat model of peripheral inflammation and hyperalgesia, dynorphin A(1-8)-like immunoreactive (DYN-LIr) spinal neurons were examined for contacts from calcitonin gene-related peptide-like immunoreactive (CGRP-LIr) varicosities using a double-label PAP method. Ipsilateral to the inflammation, CGRP-LIr varicosities contacted both dendrites and somata of DYN-LIr neurons in lumbar laminae I, II and V. Few such contacts were found on the contralateral side. The results suggest that opioid neurons which exhibit a dynamic change in dynorphin associated with inflammation, represent a subpopulation of neurons that receive contacts from presumptive nociceptive primary afferents.

The spinal projection of individual identified A-delta- and C-fibers

1. Recordings were made from individual sensory neurons with an A-delta peripheral conduction velocity, either intrasomally in the L7 dorsal root ganglion, or extracellularly in Lissauer's Tract or in the dorsal root close to the root entry zone. The spinal projection of these afferents was assessed by their antidromic response to stimulation of the dorsal columns (DC) or Lissauer's Tract (LT) at the L5/L6 border. The adequate stimulus was also ascertained. 2. A-delta-fibers could be divided into two groups: high-threshold mechanoreceptors from either skin or muscle (HTMRs) and low-threshold mechanoreceptors (LTMs), primarily Down Hairs. A third group of cells recorded intrasomally had broad spikes with shoulders on the downstroke characteristic of A-delta-nociceptors and were so classified provisionally, although no adequate stimulus could be identified. HTMRs and broad spike cells projected either in DC or LT, but LTMs projected only in DC, never in LT. About one-quarter of both groups failed to project rostrally as far as L5/L6. 3. Cells with unmyelinated axons recorded intrasomally were found to supply either low-threshold or high-threshold mechanoreceptors. Unlike A-delta-cells, all these cells had broad spikes with shoulders on the downstroke. Proportionally fewer C-fibers than A-delta-fibers projected as far as one segment rostral from their root entry zone. Of those that did, axons supplying low-threshold mechanoreceptors projected only in DC, whereas those innervating high-threshold mechanoreceptors could project either through LT or DC. 4. A-delta-fibers supplying LTMs and HTMRs exhibited a similar reduced conduction velocity was reduced even further in the spinal cord but much more for HTMRs than for LTMs. For C-fibers the conduction velocity decrease was more substantial in the dorsal root for HTMRs than for LTMs. 5. These findings suggest that axons innervating different peripheral receptors exhibit characteristic cellular properties. They confirm that the primary afferent component of Lissauer's Tract is specialized as a "pain pathway" but also indicate that the dorsal columns may play some role in the transmission of nociceptive information.

The rostral projection of small diameter primary afferents in Lissauer's tract

The rostral projection of A delta and C primary afferents in Lissauer's tract (LT) was studied by assessing how far, rostrally, axons entering at a given level could be activated by electrical stimulation. Sural A delta primary afferents in LT exhibited a rostral projection at least as far as the L3/L4 border, 4 segments rostral to their segment of entry (S1 dorsal root). C-fibers from the sural nerve projected in LT less than 2 segments rostral to their segment of entry. It is concluded that small afferent fibers can project appreciable distances along the spinal cord to bring them into regions not normally responsive to natural stimulation of the receptive field of such fibers.