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Substance P-saporin for bone cancer pain in dogs: Can man’s best friend solve the lost in translation problem in analgesic development?
Hayashida K (2013) Substance P-saporin for bone cancer pain in dogs: Can man’s best friend solve the lost in translation problem in analgesic development?. Anesthesiology 119(5):999-1000. doi: 10.1097/ALN.0b013e3182a951a2
Summary: This editorial describes the SP-SAP papers in this latest issue of Anesthesiology. The results of the paper are discussed, and the potential in using companion dogs for pain models is emphasized. While most pain models have been rodent-based, companion dogs provide models for chronic pain due to natural causes such as cancer and arthritis, along with frequent opportunity for behavioral assessments by the owner. Such assessments can be done without stress to the animal.
Related Products: SP-SAP (Cat. #IT-07)
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Intrathecal substance p-saporin in the dog: efficacy in bone cancer pain.
Brown DC, Agnello K (2013) Intrathecal substance p-saporin in the dog: efficacy in bone cancer pain. Anesthesiology 119(5):1178-1185. doi: 10.1097/ALN.0b013e3182a95188
Summary: This work demonstrates the use of naturally occurring bone cancer in dogs as a model for pain therapy. Companion dogs with bone cancer received 20-60 μg intrathecal injections of SP-SAP (currently in human clinical trials) depending on the size of the dog. Significantly more dogs in the control group required unblinding and adjustment of pain care than in the SP-SAP group, indicating the efficacy of SP-SAP in pain control. This study also demonstrates the validity of the dog model for testing analgesic protocols.
Related Products: SP-SAP (Cat. #IT-07)
Loss of neurons in rostral ventromedial medulla that express neurokinin-1 receptors decreases the development of hyperalgesia.
Khasabov SG, Simone DA (2013) Loss of neurons in rostral ventromedial medulla that express neurokinin-1 receptors decreases the development of hyperalgesia. Neuroscience 250C:151-165. doi: 10.1016/j.neuroscience.2013.06.057
Summary: Previous data has indicated that neurokinin-1 receptors are located on ON cells in the rostral ventromedial medulla (RVM). ON cells are considered pronociceptive because noxious stimulation is stimulatory. In this work the authors eliminated ON cells using 0.3-μl injections of 1 μM SSP-SAP (Cat. #IT-11) into the left and right side of the RVM. Blank-SAP (Cat. #IT-21) was used as a control. SSP-SAP treatment did not change mechanical or heat withdrawal responses, or change morphine-induced analgesia. A significant reduction in the duration of nocifensive behaviors induced by various hyperalgesic stimulators indicated that these neurons are involved in pain facilitation rather than modulation.
Related Products: SSP-SAP (Cat. #IT-11), Blank-SAP (Cat. #IT-21)
Effects of intrathecal SNC80, a delta receptor ligand, on nociceptive threshold and dorsal horn substance p release.
Kouchek M, Takasusuki T, Terashima T, Yaksh TL, Xu Q (2013) Effects of intrathecal SNC80, a delta receptor ligand, on nociceptive threshold and dorsal horn substance p release. J Pharmacol Exp Ther 347(2):258-264. doi: 10.1124/jpet.113.206573 PMID: 23978562
Summary: In this work the authors utilized three different preclinical pain models to examine the effects of intrathecal administration of the DOR agonist SNC80. One strategy was to assess NK-1 receptor (NK1r) internalization using anti-NK1r (Cat. #AB-N33AP) in IHC at a 1:3000 dilution on cryosections. The data indicate that the transmitter release from small peptidergic afferents is an effect mediated by DOR in the spinal cord.
Related Products: NK-1 Receptor Rabbit Polyclonal, affinity-purified (Cat. #AB-N33AP)
BB2 bombesin receptor-expressing spinal neurons transmit herpes-associated itch by BB2 receptor-independent signaling.
Sasaki A, Adhikari S, Andoh T, Kuraishi Y (2013) BB2 bombesin receptor-expressing spinal neurons transmit herpes-associated itch by BB2 receptor-independent signaling. Neuroreport 24(12):652-656. doi: 10.1097/WNR.0b013e32836352d8
Summary: Using a skin rash model created by inoculating mice with human herpes virus, bombesin receptor-expressing spinal neurons were lesioned intrathecally with 400 ng of Bombesin-SAP (Cat. #IT-40). Lesioned animals displayed reduced scratching, but licking (due to pain) was not reduced.
Related Products: Bombesin-SAP (Cat. #IT-40), Blank-SAP (Cat. #IT-21)
A small molecule angiotensin II type 2 receptor (AT₂R) antagonist produces analgesia in a rat model of neuropathic pain by inhibition of p38 mitogen-activated protein kinase (MAPK) and p44/p42 MAPK activation in the dorsal root ganglia
Smith MT, Woodruff TM, Wyse BD, Muralidharan A, Walther T (2013) A small molecule angiotensin II type 2 receptor (AT₂R) antagonist produces analgesia in a rat model of neuropathic pain by inhibition of p38 mitogen-activated protein kinase (MAPK) and p44/p42 MAPK activation in the dorsal root ganglia. Pain Med 14(10):1557-1568. doi: 10.1111/pme.12157 PMID: 23742186
Objective: To elucidate the mechanism through which EMA300, a small molecule antagonist of the angiotensin II type 2 receptor (AT2R) with >1,000-fold selectivity over the angiotensin II type 1 receptor, produces analgesia in a rodent model of neuropathic pain.
Summary: Augmented angiotensin II/AT2R signaling in the DRGs of CCI rats is attenuated by EMA300 to block p38 MAPK and p44/p42 MAPK activation, a mechanism with clinical validity for alleviating neuropathic pain.
Usage: Immunostaining (1:250), rat DRG sections
Related Products: Angiotensin II receptor (AT-2R) Rabbit Polyclonal, affinity-purified (Cat. #AB-N28AP)
Morphine hyperalgesia gated through microglia-mediated disruption of neuronal Cl(-) homeostasis.
Ferrini F, Trang T, Mattioli TA, Laffray S, Del’Guidice T, Lorenzo LE, Castonguay A, Doyon N, Zhang W, Godin AG, Mohr D, Beggs S, Vandal K, Beaulieu JM, Cahill CM, Salter MW, De Koninck Y (2013) Morphine hyperalgesia gated through microglia-mediated disruption of neuronal Cl(-) homeostasis. Nat Neurosci 16(2):183-192. doi: 10.1038/nn.3295
Summary: Although morphine is the drug of choice in dealing with chronic pain, it paradoxically can produce a hyperalgesic state. The authors examined the issue from several different angles. One method was to eliminate spinal microglia of rats through the intrathecal application of 16-32 μg of Mac-1-SAP (Cat. #IT-33). 20 μg of saporin (Cat. #PR-01) was used as a control. It was found that P2X4 receptors expressed by microglia were necessary for the development of morphine hyperalgesia, but not morphine tolerance.
Related Products: Mac-1-SAP rat (Cat. #IT-33), Saporin (Cat. #PR-01)
Depletion of spinal norepinephrine increases the duration of postoperative pain related behaviors following acute plantar incision and partial nerve injury in the rat.
Wang F, Eisenach JC, Peters CM (2012) Depletion of spinal norepinephrine increases the duration of postoperative pain related behaviors following acute plantar incision and partial nerve injury in the rat. Neuroscience 2012 Abstracts 785.11. Society for Neuroscience, New Orleans, LA.
Summary: Background and Objective: The percentage of patients that develop chronic postsurgical pain can range from 10-50% depending on the type of surgery. The underlying mechanisms responsible for the transition from an acute to chronic postoperative pain state are unknown. Recent clinical studies suggest that the integrity of endogenous pain inhibitory circuits may be important for preventing this transition. The descending noradrenergic transmission has well-known inhibitory effects on spinal synaptic transmission and norepinephrine has anti-inflammatory effects on spinal glial activation. We hypothesized that disrupting spinal noradrenergic fibers in rats prior to peripheral tissue injury would enhance spinal glial activity and impair resolution of postoperative pain. Methods: To test this hypothesis, we used a model of acute pain (Brennan incision model) and a model of nerve injury involving partial L5 spinal nerve ligation. We intrathecally injected dopamine β hydroxylase conjugated to the ribosomal toxin saporin (DβH-sap, 5 μg) or control (IgG-sap) to Sprague-Dawley rats 14 days prior to surgery to deplete noradrenergic fibers. Sensitivity to mechanical stimuli (von Frey) and spontaneous guarding were assessed for several weeks. We used immunohistochemistry to assess microglial (IBA1) and astrocyte (GFAP) activation in spinal cord tissue. Results: Depletion of noradrenergic fibers resulted in a significant increase in the duration of mechanical hypersensitivity in the ipsilateral paw of rats with plantar incision (6 days in IgG-sap treated rats vs. at least 21 days in DβH-sap treated rats) and partial L5 spinal nerve ligation (42 days in IgG-sap treated rats vs. at least 70 days in DβH-sap treated rats). Depletion of noradrenergic fibers did not affect mechanical withdrawal thresholds in normal rats suggesting both tissue injury and spinal noradrenergic depletion were required for prolonged mechanical hypersensitivity. The duration of spontaneous guarding following plantar incision was not affected by DβH-sap treatment. Additionally, microglia and astrocyte activation was increased in the spinal cord 21 days following incision and 70 days after nerve injury in DβH-sap treated rats compared to IgG-sap treated rats. Conclusions: These findings highlight the crucial role of spinally projecting noradrenergic pathway in the resolution of incision and nerve injury induced hypersensitivity which may be due in part to inhibitory effect of norepinephrine on spinal glial activation. Future studies will focus on the adrenergic receptor subtypes and mechanisms responsible for the transition from acute to chronic postoperative pain in these models.
Related Products: Anti-DBH-SAP (Cat. #IT-03)
Descending facilitation contributes to changes in dorsal horn gene expression in a rat model of inflammatory joint pain.
Carr F, Géranton SM, Hunt SP (2012) Descending facilitation contributes to changes in dorsal horn gene expression in a rat model of inflammatory joint pain. Neuroscience 2012 Abstracts 785.07. Society for Neuroscience, New Orleans, LA.
Summary: Chronic pain is associated with increased excitability and changes in gene expression within the dorsal horn. Descending facilitation from the rostral ventromedial medulla (RVM) is known to contribute to this excitability and behavioural hypersensitivity in a number of pain states. This would suggest that some of the gene changes associated with chronic pain could be driven by descending pathways terminating in the dorsal horn. We have previously demonstrated that ablation of a subset of RVM neurons expressing the mu opioid receptor (MOR) attenuates behavioural hypersensitivity following joint inflammation. The aim of the present study was to combine lesion of the RVM with microarray analysis of the dorsal horn to identify genes regulated by descending facilitation in this pain model. Selective lesion of MOR expressing cells of the RVM was carried out in rats by microinjection of the selective toxin dermorphin-saporin. Non-lesioned controls received vehicle microinjection. 4 weeks after the lesion procedure when depletion of the MOR+ cells was complete, both groups received an injection of 10μl Complete Freund’s Adjuvant to the left ankle joint. 7 days later the animals were sacrificed and the ipsilateral quadrant of the dorsal horn of the spinal cord lumbar region (L4-L6) removed. RNA was extracted and microarray analysis carried out using Affymetrix GeneChip Rat Gene 1.0 ST Arrays. Raw data was analysed in R using Bioconductor open source software. Limma testing was applied and a list of genes differentially regulated in animals with prior RVM lesion compared to non-lesioned controls was generated. The majority of differentially regulated genes (73%) were downregulated in the lesioned group. We used the DAVID bioinformatics resource to cluster the genes into groups with similar functional annotations (Huang et al., 2009). This analysis identified 16 gene clusters with significantly enriched functional annotations. Among these enriched functions were ribosomal function and biogenesis, inflammatory response (including the chemokine CXCL10), GPCR signalling (including the serotonin receptor 5HTR1D) and transcriptional regulation (including the transcriptional repressor RCOR2). Following on from identification of functional categories, validation of genes of interest was carried out using RT-qPCR. Our findings suggest that descending facilitation contributes to gene expression changes within the dorsal horn and that this may correlate with behavioural hypersensitivity observed in chronic pain.
Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)
Knockdown of noradrenergic locus coeruleus (LC) neurons alleviates chronic orofacial pain
Kaushal R, Ma F, Zhang L, Bright CR, Taylor BK, Westlund KN (2012) Knockdown of noradrenergic locus coeruleus (LC) neurons alleviates chronic orofacial pain. Neuroscience 2012 Abstracts 164.19. Society for Neuroscience, New Orleans, LA.
Summary: Trigeminal neuralgia (TN) is an excruciating and debilitating form of clinical orofacial pain. Noradrenergic locus coeruleus (LC, pontine A6 neurons) is involved in bidirectional modulation of pain. Multiple studies indicate that LC activity is increased during noxious stimulation and following inflammation or nerve damage. Predominantly known for its role in the feedback inhibition of pain, emerging studies also indicate a contribution of the LC in pain facilitation. For example, lesions of the LC significantly reduce tonic behavioral responses to intraplantar formalin injection, prevent autotomy, and reduce hypersensitivity associated with peripheral nerve injury. In this study we hypothesized that noradrenergic (LC) neurons contribute to the facilitation of chronic pain in TN. We used a rat model of TN involving infraorbital nerve chronic constriction injury (ION-CCI) which produces mechanical hypersensitivity as assessed by a reduction in von Frey threshold. Administration of anti-dopamine-β-hydroxylase saporin (anti-DβH-saporin) toxin was performed for selective elimination of noradrenergic LC neurons or IgG saporin (nonspecific) as the control either by intracerebroventricular (i.c.v space 2) or by bilateral spinal trigeminal nucleus (STN) injections. Under minimal restraint, rats received either no stimulation or repeated stimulation with either a 2 or 15-gm von Frey hair applied directly to the maxillary branch. Withdrawal threshold (tactile allodynia) from von Frey fiber stimulation to the face was not changed as compared to baseline in animals subjected to sham surgery; this was true in both saporin and anti-DβH-saporin groups. However, i.c.v. anti-DβH-saporin significantly increased withdrawal threshold animals with ION-CCI as compared to IgG saporin controls. More selective destruction of the LC-trigeminal pathway with bilateral STN anti-DβH-saporin injection also alleviated behavioral signs of chronic orofacial hyperalgesia. Elimination of noradrenergic LC neurons was confirmed by complete loss of tyrosine hydroxylase (TH) immunoreactivity in anti-DβH-saporin injected animals. Compared to unstimulated controls, mechanical stimulation increased immunoreactive phosphorylated extracellular cell-regulated protein kinase (pERK), a marker of neuronal activity, in the LC and STN. Nerve injury also increased expression of a neuronal injury and stress marker, activating transcription factor 3 (ATF3), in trigeminal ganglia neurons. Together, these results indicate that noradrenergic locus coeruleus neurons facilitate chronic orofacial neuropathic pain.
Related Products: Anti-DBH-SAP (Cat. #IT-03)