Contrasting genetic effects of major histocompatibility complex on ischemic peripheral nerve and spinal cord injury in female rats

We have recently shown that the major histocompatibility complex (MHC) exerts a regulatory influence on the development of neuropathic pain-like behaviors after partial sciatic nerve injury in male rats. In the present study, we assessed the role of the MHC in peripheral nerve injury-induced pain as well as central pain following spinal cord injury in female rats using the following inbred strains: Dark Agouti (DA; RT1^av1), Piebald Virol Glaxo (PVG; RT1^c) and in the MHC-congenic strain PVG–RT1^av1. In line with our previous observation in male rats, PVG–RT1^c displayed more severe allodynia compared to the strains carrying the RT1^av1 haplotype (PVG–RT1^av1 and DA–RT1^av1) following sciatic nerve injury in female rats. However, the MHC did not seem to impact the development of allodynia following spinal cord injury since the two congenic strains PVG–RT1^c and PVG–RT1^av did not differ after spinal cord injury. Interestingly, the DA–RT1^av1 strain displayed significantly more severe allodynia than both PVG strains and this difference was not explained by the extent of spinal cord injury. These results suggest that there are differences in the genetic mechanisms for neuropathic pain development following peripheral or central nervous system injury, both in regarding to the role of the MHC complex as well as non-MHC genes.     

Allospecific recognition of hemic cells in vitro by natural killer cells from athymic rats: evidence that allodeterminants coded for by single major histocompatibility complex haplotypes are recognized.

We have previously shown that large granular lymphocyte (LGL)-enriched cell populations have the capacity to spontaneously recognize and kill allogeneic small lymphocytes and bone marrow cells (BMC) in vitro in certain strain combinations of rats. Here, we have studied the alloreactivity of natural killer (NK) cells from PVG nude (RT1c) rats against a panel of major histocompatibility complex (MHC) incompatible hemic cells. Both lymphocytes and BMC from the AO (RT1u), DA (RT1a), BN (RT1n) as well as the MHC-congenic PVG-RT1u (RT1u) rat strains were efficiently killed in vitro, whereas cells from syngeneic PVG rats were spared. The structures recognized on lymphocytes and BMC were probably similar since the two cell populations inhibited each other in cross-competition experiments. A number of features aligned the alloreactive effector cells with NK cells and not T cells. (a) Only about 5% of the effector cells from nude spleens expressed the T cell antigens CD3, CD5 or T cell receptor (TcR) alpha/beta whereas greater than 50% of the cells expressed markers present on NK cells (CD2, CD8, OX52 and the rat NK cell-specific marker NKR-P1 recognized by the monoclonal antibody 3.2.3). (b) The alloreactive cells were granular since pretreatment of nude spleen cells with the lysosomotropic agent L-leucine methyl ester which eliminated LGL, simultaneously abolished the cytolysis of both allogeneic lymphocytes and YAC-1 tumor cells. (c) Nude spleen cells stimulated with human recombinant interleukin 2 for 1 week in vitro generated large granular proliferating cells which were CD3-, CD5-, TcR alpha/beta-, but greater than 95% 3.2.3+. These cells efficiently killed allogeneic hemic cells from the same rat strains as did freshly isolated effector cells. (d) The cytolysis of allogeneic hemic cells could effectively be inhibited with unlabelled NK-sensitive (YAC-1 and K-562), but not NK-resistant (Roser leukemia) tumor cells. Cross-competition studies showed that PVG nude NK cells discriminated between AO, BN and DA BMC, suggesting that different alloantigens were positively recognized by subsets of NK cells. The mode of inheritance of the allodeterminant specifically recognized on AO BMC was investigated in crosses and backcrosses between AO and BN or DA rats. A gene dosage effect was observed in that this determinant was expressed at a slightly reduced level in F1 hybrids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Partial NK cell tolerance induced by radioresistant host cells in rats transplanted with MHC-mismatched bone marrow

We have studied the effect of radioresistant host cells in inducing tolerance and adaptation of the MHC recognition repertoire of donor-derived NK cells in stem cell allotransplanted (allo-SCT) rats. Sub-lethally irradiated PVG.1AV1 rats (RT1(av1)) were transplanted with bone marrow from fully MHC-mismatched allotype-marked PVG.7B (RT1(c)) rats; MHC-identical PVG (RT1(c)) controls were transplanted in parallel. In the PVG.7B → PVG.1AV1 allogeneic chimeras, NK cells were donor derived and showed partial tolerance toward host cells. Allogeneic chimeras failed to efficiently reject PVG.1AV1 cells by an NK-mediated mechanism in vivo (allogeneic lymphocyte cytotoxicity), and IL-2-cultured NK cells derived from these chimeras showed diminished cytolytic activity against PVG.1AV1 cells in vitro. There were corresponding changes in the phenotype and function of the highly alloreactive Ly49i2(+) NK cells, which are specifically inhibited by a donor MHC class I ligand, RT1-A1(c). The ligand-negative host MHC haplotype apparently induced expression of a second uncharacterized inhibitory MHC receptor responsible for the partial tolerance toward host-derived cells, along with a modest increase in Ly49i2 receptor levels. The host MHC haplotype did not induce a general hyporesponsiveness in Ly49i2(+) NK cells, which showed normal activation responses in a panel of MHC congenic strains. The data suggest that the MHC constitution of radiation-resistant host cells can have permanent, albeit not fully tolerogenic, effects on the development of a functional NK repertoire following allo-SCT.     

Class I and class II regions of the major histocompatibility complex both contribute to individual odors in congenic inbred strains of rats

The major histocompatibility complex (MHC) of the rat has three regions—A (class I), B/D (class II), and C/E (class I)—and congenic strains are available which differ in each of these regions. We used the habituation-dishabituation procedure to examine the ability of PVG-RT1^u male rats to discriminate between the urinary odors of congenic rat strains which differ genetically only at certain individual regions of the MHC. The results of five experiments indicate that discrimination can be made between urine from rats which differ in all three regions of the MHC (PVG vs. PVG-RT1^av1 donors), only in the class I A region (PVG vs. PVG.R1 donors), only in the class I C/E region (PVG.R19 vs. PVG-RT1^av1 donors), only in the class II B/D region (PVG.R1 vs. PVG.R19 donors), and in all regions except the classical class IA locus (PVG-RT1^av1 vs. PVG.R1 donors). These results indicate that all of the MHC regions may contribute to the individual odors of rats.This research was supported by Natural Sciences and Engineering Research Council of Canada Grant A7441 (R.E.B.), the Medical Research Council of Great Britain (B.R.), and a NATO Collaborative Research Grant. P.B.S. is working under an AFRC New Initiatives Grant.     

Activation and selection of NK cells via recognition of an allogeneic, non-classical MHC class I molecule, RT1-E

Previous studies have established that NK cells express both inhibitory and activatory receptors. The inhibitory receptors have been shown to recognize major MHC class I molecules, but the physiological ligands for the activatory receptors have been only partly characterized. In this study we investigated whether NK cells could be activated by recognizing specific non-classical MHC class Ib molecules. NK cells from BN (RT1(n)) rats immunized in vivo with MHC-incompatible WF (RT1(u)) cells displayed cytolytic activity specific for product(s) of the MHC class Ib RT1-E(u) / C(u) region. These cells were shown to kill Rat2 fibroblast cells transfected with cDNA for RT1-E(u) but neither untransfected Rat2 nor a transfectant with the class Ia allele, RT1-A(u). Cytolysis of Rat2-RT1-E(u) was inhibited by the anti-RT1-E(u) antibody 70-3-C2. In addition, NK cells cytolytic against PVG (RT1(c)) targets, but not against WF (RT1(u)) or other allogeneic targets were activated after PVG immunization of BN rats. The generation of NK populations cytolytic for target cells of the same haplotype as the immunizing cells, but not for third-party targets, strongly suggests the existence of a selective NK-mediated response in vivo. We conclude that recognition of an allogeneic MHC class Ib RT1-E molecule activates NK cells and the specific cytolytic response could be regarded as adaptive.     

Genes in two major histocompatibility complex class I regions control selection, phenotype, and function of a rat Ly-49 natural killer cell subset.

We have generated a monoclonal antibody (STOK2) which reacts with an inhibitory MHC receptor on a subset of alloreactive NK cells in the rat. This receptor, termed the STOK2 antigen (Ag), belongs to the Ly-49 family of lectin-like molecules and displays specificity for the classical MHC class I molecule RT1-A1c of PVG rats. Here, we have investigated the influence of the MHC on the selection, phenotype and function of the STOK2+ NK subset in a panel of MHC congenic and intra-MHC recombinant strains. STOK2 receptor density was influenced by the presence of its classical MHC I ligand RT1-A1c, as evidenced by a reduction of STOK2 Ag on the surface of NK cells from RT1-A1c+, as compared with RT1-A1c-, strains. In addition, a role for nonclassical MHC I RT1-C/E/M alleles in the selection of the STOK2 Ag was demonstrated. The relative number of STOK2+ NK cells was fivefold higher in rats expressing the RT1-C/E/M(av1) as compared with those expressing the RT1-C/E/M(u) class Ib haplotype. The STOK2 ligand RT1-A1c inhibited cytotoxicity of STOK2+ NK cells regardless of effector cell MHC haplotype. Allospecificity of STOK2+ NK cells varied markedly with effector cell MHC, however, and suggested that inhibitory MHC I receptors apart from STOK2 were variably co-expressed by these cells. These data provide evidence for the MHC-dependent regulation of the allospecific repertoire within a subset of potentially autoreactive Ly-49+ rat NK cells.     

Long-Term Donor Chimerism after MHC (RT1) Mismatched Bone Marrow Transplantation in the Rat: the Role of Host Alloreactive NK Cells

We have investigated the role of major histocompatibility complex (MHC) (RT1) disparities in the engraftment of bone marrow (BM) cells after whole body irradiation of rats. Mononuclear BM cells from PVG.RT7.2 (RT1c) rats were injected i.v. into sublethally (10Gy) whole body irradiated PVG (RT1c) rats and RT1 congenic and recombinant PVG rats. Repopulation of the BM, spleen, and blood with donor cells was assessed by FACS analysis of cells labelled with the fluorescein isothiocyanate (FITC)-labelled HIS41 monoclonal antibody (MoAb) against the RT7.2 marker. In RT1 matched (PVG.RT7.2 --> PVG) and RT1-mismatched combinations (PVG.RT7.2 --> PVG.1AV1), where radioresistant host natural killer (NK) cells could not recognize the BM inoculum as foreign, a donor chimerism close to 100% was observed after 6-8 weeks. However, in rat strain combinations where host NK cells could recognize an RT1 mismatch, almost no donor cells survived, and the rats were repopulated with leukocytes of host origin. In intra-MHC recombinant rat strains the element determining rejection or acceptance of the allograft mapped to the RT1-B/D-C/E/M region in PVG.R8 and PVG.R23 rats, in accordance with the patterns of NK alloreactivity in these strain combinations. NK cells may therefore be a primary obstacle to successful allogeneic BM engraftment in this model.     

Strain differences in sensitivity of rats to Mycoplasma arthritidis ISR 1 infection are under multiple gene control.

At least 5 female rats from each of 24 inbred (ACI, AS, BDIX, BH, BN, BS, BUF, DA, LE, LEW, MWF, OM, SPRD-Cu3, W-Krypt, and WKY), RT1 congenic [BH.1L(LEW), LEW.1A(AVN), LEW.1C(WIST), LEW.1LV3(BH), LEW.1K(SHR), and LEW.1N(BN)], and F1 hybrid [(LEW x BN)F1, (LEW.1W x LEW.1A)F1, and (LEW x LEW.1W)F1] strains, representing eight independent major histocompatibility complex (MHC) haplotypes (a, b, c, dv1, k, l, n, and u) and five related RT1 haplotypes (av1, lv1, lv3, uv2, and uv3), were inoculated intravenously with Mycoplasma arthritidis, and the severity of the polyarthritis that developed was determined by estimating arthritis scores and weight reductions. The 24 inbred, congenic, and F1 hybrid rat strains differed considerably in their sensitivity to infection with M. arthritidis and in the severity of the polyarthritis that they developed. Statistical evaluation showed that in the acute phase (days 1 to 42 after infection) as well as in the chronic phase (days 39 to 121 after infection) of the disease, the means of the arthritis scores for the strains form a continuous variation without significant interruptions, with the very sensitive LEW rats, the RT1 congenic rats on LEW background, the F1 hybrids with LEW, and the MWF, BS, BH, and DA rats on one end and the resistant WKY, BUF, W-Krypt, LE, and OM rats on the other end. A continuous variation was also observed for the means of the growth rates. There were, however, no significant differences between the sensitive and the resistant rat strains in the antibody titers determined by complement fixation test and enzyme immunoassay. Heritabilities of arthritis scores were calculated for all strains (h2 = 0.39 to 0.62), for the RT1 congenic strains (h2 = 0.04 to 0.14), and for several strains with identical MHC genes (h2 = 0.61 to 0.93). The results show that non-MHC genes are probably responsible for the sensitivity of rats to infection with M. arthritidis.     

Induction of autoimmunity to antigens of the glomerular basement membrane in inbred Brown-Norway rats.

Induction of autoimmune antibodies against antigens of glomerular basement membrane (GBM) was studied in nine inbred strains of rats each with a different major histocompatibility complex H-1. Brown-Norway (BN) (H-1n), Lewis (H-1(1)), PVG/c (H-1c), AS2 (H-1f), AVN (H-1a), BD V (H-1d), DA (H-1a) and F344 (H-1(1)) rats were immunized with bovine GBM and Freund's complete adjuvent (CFA). A pronounced linear deposition of host IgG (IgG1 and IgG2a) along the GBM was found in BN rats. No deposition of C3 could be detected in the glomeruli nor did the animals develop proteinuria. The quantity of autoimmune antibodies fixed to the GBM was low (48 microgram +/- 14) which could explain the absence of C3 deposition and proteinuria. The antigenic specificity of the antibodies deposited along the GBM in BN rats was shown by the fixation in vitro of the eluted antibodies to the GBM and tubular basement membrane (TBM) of normal kidneys. A much weaker and irregular deposition of host IgG along the GBM was observed in PVG/c, AS2. AVN, BD V, DA and F344 rats. Of these strains, eluates from the glomeruli of PVG/c, AVN, BD V and DA rats fixed very weakly to the GBM of normal kidneys whereas eluates from AS2 and F344 rats did not fix to GBM or TBM. No deposition of host IgG was found in Lewis rats, and the eluates did not fix to normal kidneys. Congenic L.BN rats with the BN H-1n haplotype and a Lewis background did not respond. This study shows a genetic predisposition in rats to an autoimmune anti-GBM response which is not, or not exclusively, controlled by genes linked to the H-1 histo-compatibility complex.     

Macrophage and lymphocyte invasion of dorsal root ganglia after peripheral nerve lesions in the rat

The distribution of major histocompatibility complex class II (MHC II)-positive non-neuronal cells and T-lymphocytes was examined immunohistochemically in dorsal root ganglia (DRGs) up to 12 weeks following transection of one sciatic or lumbar spinal nerve in adult rats. Unlike within the brain, MHC II immunopositive (+) and T-cells are normally present within DRGs. After nerve transection, MHC II+ cell density increased (by about four times after each lesion) in DRGs projecting into lesioned nerves. Subsequently the number declined after sciatic but not spinal nerve transection. MHC II+ cells did not contain glial markers, even when these were up-regulated after the lesions. Initially, MHC II+ cells lay outside the satellite glia but, by 11 weeks, they had moved through them to lie against the somata. T-cells invaded the lesioned DRGs earlier than the MHC II+ cells. They achieved greater numbers after spinal (30 x control) than after sciatic (12 x control) nerve transection. They also increased in undamaged ganglia adjacent to the spinal nerve injury. T-cell density progressively declined after spinal but not sciatic nerve transection. Both cell types appeared to invade the DRGs initially through blood vessels and the meninges, particularly near the subarachnoid angle. At later stages, occasional neurones had dense aggregations of T-cell receptor+ and MHC II+ cells associated with them.We conclude that the magnitude and time course of changes in MHC II expression and T-cell numbers in lesioned DRGs differ from the responses within motor nuclei after axotomy. The influx of inflammatory cells may contribute to neurone survival in the short term. Their long-term presence has implications for patients. These cells have the potential to release excitatory cytokines that may generate ectopic impulse activity in sensory neurones after nerve injury and so may play a role in the generation of chronic neuropathic pain.     

Antihyperalgesic and Anti-inflammatory Effects of Atorvastatin in Chronic Constriction Injury-Induced Neuropathic Pain in Rats

Atorvastatin is a 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitor used in treatment of hypercholesterolemia and prevention of coronary heart disease. The aim of this study is to investigate the antihyperalgesic and anti-inflammatory effects of atorvastatin (3, 10, and 30 mg/kg by oral gavages for 14 days) in chronic constriction injury (CCI) model of neuropathic pain in rats. CCI caused significant increase in tumor necrosis factor-α, interleukin 1 beta, prostaglandin E2, along with matrix metalloproteases (MMP-2) and nerve growth factor (NGF) levels in sciatic nerve and spinal cord concomitant with mechanical and thermal hyperalgesia, which were significantly reduced by oral administration of atorvastatin for 14 days as compared to CCI rats. Our study demonstrated that atorvastatin attenuates neuropathic pain through inhibition of cytokines, MMP-2, and NGF in sciatic nerve and spinal cord suggesting that atorvastatin could be an additional therapeutic strategy in management of neuropathic pain.     

Synaptic plasticity in the substantia gelatinosa in a model of chronic neuropathic pain

Chronic neuropathic pain (CNP) is common after peripheral nerve injuries (PNI), but is rather refractory to available anti-pain medication. Advances in neuropathic pain research have identified cellular and molecular cues triggering the onset of neuropathic pain, but the mechanisms responsible for maintenance of chronic pain states are largely unknown. Structural changes such as sprouting of injured A-fibres into the substantia gelatinosa of the dorsal horn in the spinal cord have been proposed to relate to neuropathic pain in partial PNI models. Structural changes in central pain networks may also underlie the more persistent CNP following complete sectioning of a peripheral nerve, because this type of injury results in continuous and spontaneous afferent input to the spinal cord, which can trigger central sensitization. In the present study, the left sciatic nerve was completely sectioned and a 1-cm segment was removed to maintain a chronic pathology, whereas the right sciatic nerve was left intact. Mechanical allodynia was measured up to 84 days after injury, after which synaptic changes were studied in the lumbar substantia gelatinosa. The numbers of larger sized synaptophysin-immunoreactive presynaptic boutons were found to be increased in the substantia gelatinosa ipsilateral to the nerve injury. From these data we conclude that structural synaptic changes within the substantia gelatinosa are present months after complete nerve injury and that this plasticity may be involved in maintaining neuropathic pain states.     

Limiting-dilution analysis of the frequency of myelin basic protein-reactive T cells in Lewis, PVG/c and BN rats. Implication for susceptibility to autoimmune encephalomyelitis.

Susceptibility to experimental autoimmune encephalomyelitis (EAE), which is an autoimmune disease inducible by immunization with a brain-specific antigen in complete Freund's adjuvant (CFA), is different among strains. In an attempt to resolve the immune mechanisms by which the difference in susceptibility to EAE is regulated, we re-estimated susceptibility of several strains of rats, and the frequency of antigen-reactive T cells in each strain was determined by limiting-dilution analysis. EAE was induced in Lewis (LEW), PVG/c and BN rats using four different methods: (i) active immunization with guinea-pig myelin basic protein (GPBP) in CFA; (ii) immunization with GPBP in CFA that had been further supplemented with Mycobacterium tuberculosis H37Ra (supplemented CFA); (iii) adoptive transfer of GPBP-activated spleen cells into syngeneic rats; and (iv) transfer of a GPBP-specific T-cell line. The LEW strain was susceptible to all four methods. The PVG/c strain was resistant to immunization with GPBP in conventional CFA (GPBP/conv. CFA), but was susceptible to immunization with GPBP in supplemented CFA (GPBP/suppl. CFA) and to transfer of activated spleen cells. The BN strain was resistant to all methods. Limiting-dilution analysis using T cells from LEW, PVG/c or BN rats has revealed that each strain of rat displays a different pattern of frequencies of GPBP-reactive or the 68-88 sequence (GP68-88)-reactive T cells. LEW rats showed relatively high frequencies of GPBP-reactive and GP68-88-reactive T cells after immunization with either GPBP/conv. CFA or GPBP/suppl. CFA, symptomatic rats showing higher values than asymptomatic rats. In asymptomatic PVG/c rats, the frequency of GP68-88-reactive T cells was lower than that of GPBP-reactive T cells. In PVG/c rats with clinical EAE, however, GP68-88-reactive T cells increased in frequency and were almost the same as GPBP-reactive T cells. BN rats, on the other hand, responded very poorly not only to the GP68-88 sequence but also to the whole GPBP molecule, even after immunization with GPBP/suppl. CFA. These findings, obtained by limiting-dilution analysis, strongly suggest that the development of EAE in LEW, PVG/c and BN rats is closely related to the frequency of GPBP-reactive T cells. Furthermore, it is shown that resistance to EAE found in PVG/c and BN rats may be generated by different immune mechanisms.     

Genetics of the rat CT system: its apparent complexity is a consequence of cross-reactivity between the distinct MHC class I antigens RT1.C and RT1.A

The rat CT antigens are a system of medial histocompatibility antigens linked to RT1, the rat major histocompatibility complex (MHC). They have aroused interest firstly because, despite their extreme serological weakness, they are targets for 'unrestricted' cytotoxic T lymphocytes (CTL); and secondly because they have appeared to represent a complex genetic system in terms both of the number of genetic loci involved and the number of distinguishable antigenic specificities expressed. The CT system was originally defined by the reactions of LEW anti-F344 (RT1l anti-RT1lv1) secondary in vitro CTL. These CTL reacted strongly on DA(RT1av1) targets, but much more weakly on AUG or PVG (RT1c) targets. We have used the recently derived RT1 recombinant rat strains PVG.R19 (RT1.Aav1Iav1Cc) and PVG.R20 (RT1.AcIcCav1) to investigate the genetic control of this system. Contrary to previous interpretations, the results are consistent with a model in which CT is a single locus, which maps to the RT1.C region. In addition, our results demonstrate that there is cross-reactivity of anti-RT1C CTLs on RT1A products, and we suggest that the earlier placement of a CT locus in the RT1.A region was probably incorrect and a consequence of this cross-reactivity.     

Analgesic effect of intrathecally γ-aminobutyric acid transporter-1 inhibitor NO-711 administrating on neuropathic pain in rats

To investigate the analgesic effect of intrathecally administered γ-aminobutyric acid (GABA) transporter-1 inhibitor NO-711 on the sciatic nerve chronic constriction injury (CCI) rats. 5 days after intrathecal catheter placement, neuropathic pain model was established by CCI of sciatic nerve on rats. Withdrawal thresholds for mechanical allodynia and latency for thermal hyperalgesia were measured in all animals. All rats operated upon for CCI displayed decreased withdrawal thresholds for mechanical allodynia and latency for thermal hyperalgesia, which has significant difference compared with sham groups. After intrathecal NO-711 administration, withdrawal thresholds and latency were significantly increased on CCI rats compared with control group after 1 day. The results show that GABA transporter-1 inhibitor could effectively develop analgesic effect in sciatic nerve CCI rats’ model.     

Changes of expression of glial cell line-derived neurotrophic factor and its receptor in dorsal root ganglions and spinal dorsal horn during electroacupuncture treatment in neuropathic pain rats

Injury to the nervous system occasionally leads to intense and persistent neuropathic pain, which is resistant to conventional analgesic methods. It was reported that electroacupuncture (EA) had potent analgesic effect on neuropathic pain by activating various endogenous transmitters such as the opioid peptides. Glial cell line-derived neurotrophic factor (GDNF) has been hypothesized to play an important role in modulation of nociceptive signals especially during neuropathic pain state. Using immunohistochemistry, Western blot, and RT-PCR analysis techniques, the present study observed the effects of EA on the expression of GDNF and GDNF family receptor alpha-1 (GFRalpha-1, the high-affinity receptor of GDNF) in neuropathic pain rats. The results showed that both protein and mRNA levels of GDNF and GFRalpha-1 in the dorsal root ganglions (DRG), as well as GDNF protein in the spinal dorsal horn, were significantly increased after chronic constriction injury (CCI) of the rats' sciatic nerve and could be further enhanced by EA treatment. The present data demonstrated that EA could activate endogenous GDNF and GFRalpha-1 system of neuropathic pain rats and this might underlie the effectiveness of EA in the treatment of neuropathic pain.     

Antihyperalgesic and antiallodynic effect of sirolimus in neuropathic pain and the role of cytokines in this effect

Recent studies have revealed that T lymphocytes play a role in neuropathic pain following nerve injury in rats through releasing several cytokines. Sirolimus is an immunosuppressive antibiotic inhibiting T cell activation. This study aimed to determine the effect of sirolimus on hyperalgesia and allodynia and on serum and spinal cord TNF-α, IL-1β and IL-6 levels in rat neuropathic pain. Neuropathic pain was induced by loose ligation of the sciatic nerve and evaluated by tests measuring the mechanical hyperalgesia and allodynia. Sirolimus (0.75 and 1.5 mg/kg) was administered intraperitoneally once every 3 days for 2 weeks (7 doses totally). This dosing regimen revealed acceptable blood concentrations in neuropathic rats. Chronic constriction injury of the sciatic nerve resulted in hyperalgesia and allodynia. Serum levels of cytokines remained unchanged in neuropathic rats. However, TNF-α, but not IL-1β or IL-6, protein level was increased in the spinal cord tissue as evaluated by Western blotting analysis. Treatment with sirolimus resulted in antihyperalgesic and antiallodynic effects and prevented the increased spinal cord TNF-α level. It seems that sirolimus could be a promising immunosuppressive agent in the treatment of neuropathic pain.     

Patterns of expression of class I antigens in the tissues of congenic strains of rat

A comparative study of expression of class I major histocompatibility (MHC) antigens among lung, spleen, kidney, heart, liver, and brain tissues of the rat was performed. Monoclonal antibodies (MAbs) against RT1Aa determinants were conjugated to 125I and applied to frozen sections. Resulting autoradiograms showed antigen reactivity in lymphoid tissue, bronchial and alveolar epithelium, and endothelium of the lung. The lymphoid tissue of the lung and spleen demonstrated the antigen after shorter autoradiographic exposures than was required for the epithelial components of these organs. The kidneys were heavily labeled over the glomeruli, but less intensely over the tubular epithelium. RT1A antigen content of capillary endothelium of the heart was demonstrable before that of the muscle bundles. In the liver, autoradiographic sections revealed high determinant density in sinusoidal regions. Brain sections show reproducibly low levels of labeling, with the exception of vascular structures. All of these tissues from PVG-RT1c and PVG-RT1u animals show only background labeling.     

大鼠坐骨神经受压和解压后背根节和脊髓内神经元nNOS表达的变化

目的 :观察坐骨神经受压及解压后大鼠腰段背根节和脊髓内神经元型一氧化氮合酶 (nNOS)表达的变化 ,借以探讨外周神经源性痛的发病和影响机制。方法 :大鼠随机分为压迫组、解压组和对照组 ,采用聚乙烯管压迫坐骨神经的动物模型 ,用免疫细胞化学方法并结合计算机图像分析进行研究。结果 :与对照组比较 ,压迫组和解压组腰4～ 6背根节中nNOS的表达显著增加 ,相应节段脊髓背角的表达则明显降低 ;解压组与压迫组比较 ,背根节中nNOS的表达明显减少 ,而脊髓背角的已经下调的nNOS表达则回升 ,但仍然低于对照组水平。结论 :NO可能与神经源性痛时在中枢和外周的痛觉敏感性形成和神经系统长时程改变有关。     

Different patterns of morphological changes in the hippocampus and dentate gyrus accompany the differential expression of disability following nerve injury

Physical and psychological trauma which results in mood disorders and the disruption of complex behaviours is associated with reductions in hippocampal volume. Clinical evaluation of neuropathic pain reveals mood and behavioural change in a significant number of patients. A rat model of neuropathic injury results in complex behavioural changes in a subpopulation (~30%) of injured rats; these changes are co‐morbid with a range of other ‘disabilities’. The specific objective of this study was to determine in rats the morphology of the hippocampus and dentate gyrus in individuals with and without complex behavioural disruptions following a constriction injury of the sciatic nerve, and to determine whether rats that develop disabilities following nerve injury have a reduced hippocampal volume compared with injured rats with no disabilities. The social behaviours of nerve‐injured rats were evaluated before and after nerve injury. The morphology of the hippocampus of rats with and without behavioural disruptions was compared in serial histological sections. Single‐housing and repeated social‐interaction testing had no effect on the morphology of either the hippocampus or the dentate gyrus. Rats with transient or ongoing disability identified by behavioural disruption following sciatic nerve injury, show bilateral reductions in hippocampal volume, and lateralised reduction in the dentate gyrus (left side). Disabled rats display a combination of behavioural and physiological changes, which resemble many of the criteria used clinically to diagnose mood disorders. They also show reductions in the volume of the hippocampus similar to people with clinically diagnosed mood disorders. The sciatic nerve injury model reveals a similarity to the human neuropathic pain presentation presenting an anatomically specific focus for the investigation of the neural mechanisms underpinning the co‐morbidity of chronic pain and mood disorder.