- Home
- Knowledge Base
- Search Results for pain
Changes in neurokinin-1 receptor expression in populations of spinal lamina I neurons in rats lacking non-peptidergic nociceptive fibers
Saeed AW, Ribeiro-Da-Silva A (2007) Changes in neurokinin-1 receptor expression in populations of spinal lamina I neurons in rats lacking non-peptidergic nociceptive fibers. Neuroscience 2007 Abstracts 821.4/FF19. Society for Neuroscience, San Diego, CA.
Summary: Neurokinin-1 receptor (NK-1r)-containing lamina I projection neurons are deeply involved in the transmission of pain-related information to the brain. Previous studies have shown that lamina I neurons can be classified morphologically into fusiform, pyramidal and multipolar cells, and that these types differ in functional properties, with the pyramidal type being non-nociceptive. Our laboratory has shown not only a considerable increase in immunoreactivity for the NK-1r in animals with CFA-induced arthritis but also a de novo expression of these receptors by pyramidal neurons (Almarestani et al., Soc.Neurosci.Abstr., Program # 249.11, 2006). Based on this, we deemed it interesting to study whether pyramidal neurons would also express NK-1r in an animal model in which we have previously shown a drastic increase in NK-1r expression but no augmented nociceptive responses. To achieve this, we injected, under anesthesia, saporin (SAP) conjugated to the lectin IB4 into the left sciatic nerve of male Sprague Dawley rats to selectively lesion the non-peptidergic nociceptive C-fibers. Animals were sacrificed from 2 weeks to 2 months post-lesion. Horizontal sections of spinal segments L5 and L6 were cut and processed for IB4 binding and NK-1r immunoreactivity using immunofluorescence. Examination of IB4-SAP treated rats at several time points post-lesion revealed increased expression of NK-1r by lamina I cells of the fusiform and multipolar types on the side ipsilateral to the lesion, compared to the contralateral side and to controls. However, pyramidal cells seldom expressed the NK-1r in both control and lesioned animals. Surprisingly, we also observed a direct innervation of lamina I neurons by IB4-positive neurons in control animals, which did not occur ipsilaterally in lesioned animals. These observations support the concept that increased activity by the peptidergic nociceptive afferents may be important in the maintenance of nociceptive responses in the absence of non-peptidergic fibers.
Related Products: IB4-SAP (Cat. #IT-10)
ERK1/2 regulates microglia-neuron signaling and pain by PGE2 following SCI
Hains BC, Zhao P, Waxman S (2007) ERK1/2 regulates microglia-neuron signaling and pain by PGE2 following SCI. Neuroscience 2007 Abstracts 287.16/LL14. Society for Neuroscience, San Diego, CA.
Summary: We recently showed that microglia become activated after experimental SCI and dynamically maintain hyperresponsiveness of spinal cord nociceptive neurons and pain-related behaviors. Mechanisms of signaling between microglia and neurons that help to maintain abnormal pain processing are unknown. In this study, adult male Sprague Dawley rats underwent T9 spinal cord contusion injury. Four weeks after injury when lumbar dorsal horn multireceptive neurons became hyperresponsive and when behavioral nociceptive thresholds to mechanical and thermal stimuli were decreased, we tested the hypothesis that prostaglandin E2 (PGE2) contributes to signaling between microglia and neurons. Immunohistochemical data showed specific localization of phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2), an upstream regulator of PGE2 release, to microglial cells and a neuronal localization of the PGE2 receptor E-prostanoid 2 (EP2). Enzyme immunoassay analysis showed that PGE2 release was dependent on microglial activation and ERK1/2 phosphorylation. Pharmacological antagonism of PGE2 release was achieved with the mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor PD98059 and the microglial inhibitor minocycline. Cyclooxygenase-2 expression in microglia was similarly reduced by MEK1/2 inhibition. PD98059 and EP2 receptor blockade with AH6809 resulted in a decrease in hyperresponsiveness of dorsal horn neurons and partial restoration of behavioral nociceptive thresholds. Selective targeting of dorsal horn microglia with the Mac-1-SAP immunotoxin resulted in reduced microglia staining, reduction in PGE2 levels, and reversed pain-related behaviors. On the basis of these observations, we propose a PGE2-dependent, ERK1/2-regulated microglia-neuron signaling pathway that mediates the microglial component of pain maintenance after injury to the spinal cord.
Related Products: Mac-1-SAP rat (Cat. #IT-33)
Effects of systemic bicuculline on the formalin-induced nociceptive response in the lip and c-Fos expression in the SP-Saporin-treated rats
Masawaki A, Sugiyo S, Shimoda T, Sakai Y, Ohyamaguchi A, Uehashi D, Moritani M, Yoshida A, Niwa H, Takemura M (2007) Effects of systemic bicuculline on the formalin-induced nociceptive response in the lip and c-Fos expression in the SP-Saporin-treated rats. Neuroscience 2007 Abstracts 186.16/RR16. Society for Neuroscience, San Diego, CA.
Summary: This study examines the effect of systemic bicuculline (2 mg/kg, ip) on formalin-induced pain-related behavior in the lip (PRB; face scrubbing behavior) and c-Fos expression in the trigeminal nucleus caudalis (SpVc) 2hrs after formalin injection and 2-4 weeks after intra cisterna magna (i.c.m.) injection of substance P (SP) conjugated to neurotoxin, saporin (SP-Sap; 3 µM, 5 µl), blank-Sap- or saline-treatment. In SP-Sap-treated rats, the number of NK-1- immunoreactive (NK-1-IR) neurons in lamina I of the SpVc decreased compared with that of saline- or blank-Sap-treated rats. In SP-Sap-treated rats, PRB at phase 2 decreased compared with that of saline- or blank-Sap-treated rats. In SP-Sap-treated rats, the number of c-Fos-IR cells in the VcI/II decreased compared with that in the saline- or blank-Sap-treated rats. In saline- and blank-Sap- treated rats but not SP-Sap-treated rats, systemic bicuculline decreased the number of PRB at phase 2. These results indicate that i.c.m. injection of SP-Sap eliminates NK-1-bearing neurons in L1 of SpVc, and that NK-1-bearing neurons in the SpVc have pivotal role in formalin-induced PRB at phase 2 and c-Fos expression in the SpVc. The decremental effects of systemic bicuculline on the formalin-induced nociceptive responses at phase 2 and c-Fos expression in the VcI/II are secure in the presence of NK-1 receptor bearing neurons in the Vc.
Related Products: SP-SAP (Cat. #IT-07)
Superficial NK1 expressing spinal dorsal horn neurones modulate inhibitory neurotransmission mediated by spinal GABA(A) receptors.
Rahman W, Sikander S, Suzuki R, Hunt SP, Dickenson AH (2007) Superficial NK1 expressing spinal dorsal horn neurones modulate inhibitory neurotransmission mediated by spinal GABA(A) receptors. Neurosci Lett 419:278-283. doi: 10.1016/j.neulet.2007.04.039
Summary: It has been shown that elimination of lamina 1 NK1 receptor-expressing neurons affects pain behaviors. The authors investigated whether eliminating these neurons would alter GABAergic spinal inhibitory systems. Rats received 10-µl injections of 10-µM SP-SAP (Cat. #IT-07) into the L4-5 regions. Data generated by electrical and mechanical stimuli suggest that although GABAergic transmission is dependent on NK1 receptor-expressing neurons, loss of these cells results in a decrease in spinal cord excitability.
Related Products: SP-SAP (Cat. #IT-07)
Extracellular signal-regulated kinase-regulated microglia-neuron signaling by prostaglandin E2 contributes to pain after spinal cord injury.
Zhao P, Waxman SG, Hains BC (2007) Extracellular signal-regulated kinase-regulated microglia-neuron signaling by prostaglandin E2 contributes to pain after spinal cord injury. J Neurosci 27:2357-2368. doi: 10.1523/JNEUROSCI.0138-07.2007 PMID: 17329433
Summary: Spinal cord injury frequently leads to the development of long-term chronic pain. Recent data has shown that activated microglia are involved in the maintenance of this pain state. Following a spinal cord contusion injury rats were treated with a 36-µg injection of Mac-1-SAP (Cat. #IT-06) into the lumbar enlargement. Treated animals were found to have reduced microglial staining, reduction in prostaglandin E2 levels, and fewer pain-related behaviors.
Related Products: Mac-1-SAP mouse/human (Cat. #IT-06), Antibody to Mac-1 (Cat. #AB-N06)
Neuronal nitric oxide synthase is upregulated in a subset of primary sensory afferents after nerve injury which are necessary for analgesia from alpha2-adrenoceptor stimulation.
Ma W, Eisenach JC (2007) Neuronal nitric oxide synthase is upregulated in a subset of primary sensory afferents after nerve injury which are necessary for analgesia from alpha2-adrenoceptor stimulation. Brain Res 1127(1):52-58. doi: 10.1016/j.brainres.2006.10.008
Summary: Peripheral nerve injury resulting in neuropathic pain often responds poorly to opioid treatment. alpha2-adrenoreceptor (AR) agonists, however, perform better after this type of injury. After a spinal nerve ligation, rats were treated with a 0.6 µg-intrathecal injection of 192-saporin (Cat. #IT-01). The increase of neuronal nitric oxide synthase (nNOS) caused by spinal ligation was abolished in the lesioned animals. The data indicate that AR agonists may reduce sensitization by activating nNOS fibers in the superficial dorsal horn.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Substance P-saporin down-regulates substance P receptor immunoreactive sensory dorsal root ganglion neurons innervating the lumbar intervertebral discs in rats.
Ohtori S, Inoue G, Koshi T, Ito T, Doya H, Moriya H, Takahashi K (2006) Substance P-saporin down-regulates substance P receptor immunoreactive sensory dorsal root ganglion neurons innervating the lumbar intervertebral discs in rats. Spine 31:2987-2991. doi: 10.1097/01.brs.0000250306.12996.fa
Summary: Neurokinin-1 (NK-1) receptor expressing neurons that innervate lumbar intervertebral discs may be involved in lower back pain. Here the authors investigate the basic effect of SP-SAP (Cat. #IT-07) on neurons innervating the L5/6 intervertebral disc. Rats were injected with 175 ng of SP-SAP. The number of NK-1 receptor expressing neurons was reduced by over 75% in the treated animals, demonstrating SP-SAP as a useful tool to investigate the mechanism of discogenic low back pain, particulary for investigating behavioral impacts.
Related Products: SP-SAP (Cat. #IT-07)
Spinal NK-1 receptor expressing neurons mediate opioid-induced hyperalgesia and antinociceptive tolerance via activation of descending pathways.
Vera-Portocarrero LP, Zhang ET, King T, Ossipov MH, Vanderah TW, Lai J, Porreca F (2007) Spinal NK-1 receptor expressing neurons mediate opioid-induced hyperalgesia and antinociceptive tolerance via activation of descending pathways. Pain 129:35-45. doi: 10.1016/j.pain.2006.09.033
Summary: Administration of opioids can induce hyperalgesia in humans and other mammals. In this work the authors examined the role of NK-1 receptor-expressing neurons in the spinal dorsal horn during a hyperalgesic condition not induced by tissue injury. 5 µl of 10 µM SP-SAP (Cat. #IT-07) was injected into the intrathecal space of rats. Saporin (Cat. #PR-01) was used as a control. Osmotic pumps then delivered morphine. Data from the lesioned animals indicate that NK-1 receptor-expressing neurons play a critical role in this hyperalgesic circuit.
Related Products: SP-SAP (Cat. #IT-07), Saporin (Cat. #PR-01)
Molecular changes in the dorsal horn that maintain inflammatory hyperalgesia are similar to those generated during long-term potentiation
Wong YM, Webber MJ, Dickenson AH, Hunt SP (2006) Molecular changes in the dorsal horn that maintain inflammatory hyperalgesia are similar to those generated during long-term potentiation. Neuroscience 2006 Abstracts 642.17. Society for Neuroscience, Atlanta, GA.
Summary: The generation of LTP in deep dorsal horn neurons by noxious stimulation may be one mechanism whereby acute pain transforms into a chronic pain state. Spinal LTP requires the activation of a subset of superficial dorsal horn neurons that express the neurokinin-1 receptor (NK1-R) and are crucial for the initiation and maintenance of chronic pain states. These neurons participate in local spinal sensory processing and are the origin of a spino-bulbo-spinal loop that drives descending spinal facilitation. Spinal LTP is correlated with increased neuronal expression of the transcription factor zif268 in the superficial dorsal horn. Here, we examined if inflammatory pain states required LTP-like changes in gene expression that are dependent upon an intact lamina I pathway. We also asked if changing levels of zif268 regulated the glucocorticoid receptor (GR) gene, a downstream target of zif268. NK1 expressing neurons in lamina I of the lumbar spinal cord were selectively ablated using SP-SAP applied intrathecally. 28d later, rats were injected with Complete Freunds’ Adjuvant (CFA) (50%, 100μl) 2h prior to perfusion with 4% paraformaldehyde. Using immunohistochemistry, we found that while levels of c-fos immunoreactivity were unchanged by lamina I ablation, the levels of zif268 had decreased by 36% (p<0.05) compared to controls. We therefore treated rats intrathecally with zif268 antisense or missense oligonucleotides (0.16μg/μl/h) via implanted osmotic mini pumps and assessed the behavioural effects of zif268 ‘knockdown’ on inflammatory hyperalgesia. Animals were perfused 4 days after CFA inflammation and protein levels of zif268 and GR were assessed by immunohistochemistry. Antisense, but not missense zif268 treatment, reduced the levels of zif268 by 37% and reduced behavioural allodynia by 40%, but only at days 2-4 post CFA. Levels of GR were also reduced by 30% following zif268 antisense treatment. We therefore applied antisense and missense GR probes intrathecally.This reduced the inflammatory hyperalgesia score by 38% but again only on days 2-4. These results suggest the zif268 gene is essential for the maintenance but not the induction of inflammatory pain states and that zif268 can regulate GR in the spinal cord.
Related Products: SP-SAP (Cat. #IT-07)
Ascending and descending pathways support fentanyl-induced pain hypersensitivity with and without a surgical incision
Rivat C, Vera-Portocarrero LP, Ibrahim MM, Mata HP, Stagg NJ, De Felice M, Porreca F, Malan TP (2006) Ascending and descending pathways support fentanyl-induced pain hypersensitivity with and without a surgical incision. Neuroscience 2006 Abstracts 248.10. Society for Neuroscience, Atlanta, GA.
Summary: Acutely administered the analgesic opioid fentanyl has been shown to enhance mechanical hypersensitivity in a model of surgical pain induced by hindpaw incision in the rat. Recent evidence showed the importance of descending pathways originating from the rostral ventromedial medulla (RVM) in opioid-induced hyperalgesia after sustained morphine administration. Such hyperalgesia is also associated with numerous neurochemical changes in primary afferent fibers and spinal dorsal horn, such as increased spinal dynorphin expression. These changes may activate ascending pathways, mediated in part by NK-1 neurotransmission. Here, we examined the roles of ascending and descending pathways in sensory hypersensitivity after acute fentanyl administration. Male Sprague-Dawley rats received 4 fentanyl (4×100 μg/kg, s.c.) or saline injections administered at 15 min intervals. Some animals also received an incision in the plantar hindpaw. Thermal hyperalgesia and tactile allodynia were measured daily. In control rats, fentanyl induced analgesia followed by an immediate and long-lasting hyperalgesia, as previously described. Fentanyl also enhanced pain sensitivity induced by plantar incision. In SP-saporin pretreated rats, fentanyl induced analgesia and a moderate long-lasting hyperalgesia. The SP-saporin pretreatment slightly reduced both hyperalgesia and allodynia in postoperative rats and, to a larger extent, in fentanyl treated rats. Lidocaine injection in the RVM completely reversed fentanyl-induced sensory hypersensitivity and fentanyl enhancement of incision-induced hyperalgesia and allodynia. A slight reduction of incision-induced sensory hypersensitivity was observed after lidocaine injection in rats without fentanyl pretreatment. Spinal dynorphin content increased by 30 ± 7% and 71 ± 33% in fentanyl and fentanyl/incision treated rats, respectively. These data support the crucial role of the descending pathways from the RVM in the fentanyl-induced hyperalgesia and the partial implication of the NK-1 receptor containing ascending pathways.
Related Products: SP-SAP (Cat. #IT-07)