ABSTRACT
Cocaine- and amphetamine-regulated transcript (CART) peptides are involved in several physiological and pathological processes, but their mechanism of action is unrevealed due to the lack of identified receptor(s). We provided evidence for the antihyperalgesic effect of CART(55-102) by inhibiting dipeptidyl-peptidase 4 (DPP4) in astrocytes and consequently reducing neuroinflammation in the rat spinal dorsal horn in a carrageenan-evoked inflammation model. Both naturally occurring CART(55-102) and CART(62-102) peptides are present in the spinal cord. CART(55-102) is not involved in acute nociception but regulates spinal pain transmission during peripheral inflammation. While the full-length peptide with a globular motif contributes to hyperalgesia, its N-terminal inhibits this process. Although the anti-hyperalgesic effects of CART(55-102), CART(55-76), and CART(62-76) are blocked by opioid receptor antagonists in our inflammatory models, but not in neuropathic Seltzer model, none of them bind to any opioid or G-protein coupled receptors. DPP4 interacts with Toll-like receptor 4 (TLR4) signalling in spinal astrocytes and enhances the TLR4-induced expression of interleukin-6 and tumour necrosis factor alpha contributing to inflammatory pain. Depending on the state of inflammation, CART(55-102) is processed in the spinal cord, resulting in the generation of biologically active isoleucine-proline-isoleucine (IPI) tripeptide, which inhibits DPP4, leading to significantly decreased glia-derived cytokine production and hyperalgesia.
Subject(s)
Hyperalgesia , Toll-Like Receptor 4 , Rats , Animals , Hyperalgesia/metabolism , Dipeptidyl Peptidase 4 , Isoleucine , Nociception , Pain/metabolism , Peptide Fragments/pharmacology , Spinal Cord/metabolism , Inflammation/metabolismABSTRACT
The rostral migratory stream (RMS) is viewed as a glia-enriched conduit of forward-migrating neuroblasts in which chemorepulsive signals control the pace of forward migration. Here we demonstrate the existence of a scaffold of neurons that receive synaptic inputs within the rat, mouse, and human fetal RMS equivalents. These neurons express secretagogin, a Ca2+-sensor protein, to execute an annexin V-dependent externalization of matrix metalloprotease-2 (MMP-2) for reconfiguring the extracellular matrix locally. Mouse genetics combined with pharmacological probing in vivo and in vitro demonstrate that MMP-2 externalization occurs on demand and that its loss slows neuroblast migration. Loss of function is particularly remarkable upon injury to the olfactory bulb. Cumulatively, we identify a signaling cascade that provokes structural remodeling of the RMS through recruitment of MMP-2 by a previously unrecognized neuronal constituent. Given the life-long presence of secretagogin-containing neurons in human, this mechanism might be exploited for therapeutic benefit in rescue strategies.
Subject(s)
Calcium/metabolism , Matrix Metalloproteinase 2/genetics , Neuroglia/metabolism , Neurons/metabolism , Olfactory Bulb/metabolism , Secretagogins/genetics , Animals , Annexin A5/genetics , Annexin A5/metabolism , Cell Movement , Fetus , Gene Expression Regulation , Humans , Male , Matrix Metalloproteinase 2/metabolism , Mice , Microtomy , Neuroglia/ultrastructure , Neurons/ultrastructure , Olfactory Bulb/cytology , Primary Cell Culture , Rats , Rats, Wistar , Secretagogins/metabolism , Synapses/metabolism , Synapses/ultrastructure , Tissue Culture TechniquesABSTRACT
It has been hypothesized that α2-adrenoceptors (α2-ARs) may be involved in the pathomechanism of colitis; however, the results are conflicting because both aggravation and amelioration of colonic inflammation have been described in response to α2-AR agonists. Therefore, we aimed to analyze the role of α2-ARs in acute murine colitis. The experiments were carried out in wild-type, α2A-, α2B-, and α2C-AR knockout (KO) C57BL/6 mice. Colitis was induced by dextran sulfate sodium (DSS, 2%); alpha2-AR ligands were injected i.p. The severity of colitis was determined both macroscopically and histologically. Colonic myeloperoxidase (MPO) and cytokine levels were measured by enzyme-linked immunosorbent assay and proteome profiler array, respectively. The nonselective α2-AR agonist clonidine induced a modest aggravation of DSS-induced colitis. It accelerated the disease development and markedly enhanced the weight loss of animals, but did not influence the colon shortening, tissue MPO levels, or histologic score. Clonidine induced similar changes in α2B- and α2C-AR KO mice, whereas it failed to affect the disease activity index scores and caused only minor weight loss in α2A-AR KO animals. In contrast, selective inhibition of α2A-ARs by BRL 44408 significantly delayed the development of colitis; reduced the colonic levels of MPO and chemokine (C-C motif) ligand 3, chemokine (C-X-C motif) ligand 2 (CXCL2), CXCL13, and granulocyte-colony stimulating factor; and elevated that of tissue inhibitor of metalloproteinases-1. In this work, we report that activation of α2-ARs aggravates murine colitis, an effect mediated by the α2A-AR subtype, and selective inhibition of these receptors reduces the severity of gut inflammation.
Subject(s)
Adrenergic alpha-2 Receptor Antagonists/pharmacology , Colitis/chemically induced , Colitis/drug therapy , Dextran Sulfate/pharmacology , Intestines/drug effects , Receptors, Adrenergic, alpha-2/metabolism , Adrenergic alpha-2 Receptor Antagonists/therapeutic use , Animals , Clonidine/pharmacology , Clonidine/therapeutic use , Colitis/metabolism , Colitis/physiopathology , Drinking/drug effects , Female , Gene Knockout Techniques , Imidazoles/pharmacology , Imidazoles/therapeutic use , Intestinal Mucosa/metabolism , Intestines/pathology , Isoindoles/pharmacology , Isoindoles/therapeutic use , Locomotion/drug effects , Male , Mice , Mice, Inbred C57BL , Receptors, Adrenergic, alpha-2/deficiency , Receptors, Adrenergic, alpha-2/geneticsABSTRACT
Glucagon-like peptide-1 receptor (GLP-1R) agonists are now commonly used to treat type 2 diabetes and obesity. GLP-1R signaling in the spinal cord has been suggested to account for the mild tachycardia caused by GLP-1R agonists, and may also be involved in the therapeutic effects of these drugs. However, the neuroanatomy of the GLP-1/GLP-1R system in the spinal cord is still poorly understood. Here we applied in situ hybridization and immunohistochemistry to characterize this system, and its relation to cholinergic neurons. GLP-1R transcript and protein were expressed in neuronal cell bodies across the gray matter, in matching distribution patterns. GLP-1R-immunolabeling was also robust in dendrites and axons, especially in laminae II-III in the dorsal horn. Cerebrospinal fluid-contacting neurons expressed GLP-1R protein at exceedingly high levels. Only small subpopulations of cholinergic neurons expressed GLP-1R, including a subset of sympathetic preganglionic neurons at the rostral tip of the intermediolateral nucleus. GLP-1 axons innervated all regions where GLP-1R neurons were distributed, except laminae II-III. Scattered preproglucagon (Gcg) mRNA-expressing neurons were identified in the cervical and lumbar enlargements. The results will facilitate further studies on how GLP-1 regulates the sympathetic system and other autonomic and somatic functions via the spinal cord.
Subject(s)
Glucagon-Like Peptide 1 , Glucagon-Like Peptide-1 Receptor , Spinal Cord , Animals , Glucagon-Like Peptide-1 Receptor/metabolism , Glucagon-Like Peptide-1 Receptor/genetics , Male , Spinal Cord/metabolism , Mice , Glucagon-Like Peptide 1/metabolism , Cholinergic Neurons/metabolism , Proglucagon/metabolism , Proglucagon/genetics , Mice, Inbred C57BL , Axons/metabolismABSTRACT
The primary goal of this study was to map the transverse distribution of local excitatory and inhibitory synaptic inputs to mouse lamina I spinal dorsal horn neurons, using laser scanning photostimulation. A sample of lamina II neurons was also studied for comparison. Lamina I neurons received excitatory synaptic input from both laminae I-II and the outer part of III-IV, especially the II/III border region, while the inhibitory input zones were mostly confined within I-II. The excitatory synaptic input zones showed a pronounced medial asymmetry, which was correlated with a matching asymmetry in the dendritic fields of the neurons. Inhibitory input from laminae III-IV was found in a subpopulation of neurons occupying a highly restricted zone, essentially one cell layer thick, immediately below the lamina I/II border, with morphological and physiological properties that were distinct from other laminar populations in the superficial dorsal horn, and that suggest a critical role in interlaminar communication. This subpopulation also received excitatory input from laminae III-IV. Within this subpopulation, inhibitory III-IV input was correlated with the presence of long ventral dendrites. Correlations between the distribution of synaptic input zones and dendritic fields support the concept that interlaminar communication is mediated in part via contacts made onto ventrally extending dendrites of superficial laminae neurons. The results point to the presence of cell type specificity in dorsal horn circuitry, and show how the study of connectivity can itself help identify previously unrecognized neuronal populations.
Subject(s)
Posterior Horn Cells/physiology , Spinal Cord/physiology , Animals , Lasers , Mice , Mice, Inbred C57BL , Photic StimulationABSTRACT
Ample evidence indicates that in several mammalian species the pineal body contains neurons. In adult white albino rats neurons are not present in the pineal body; however, in perinatal rats many neurons were described. It was demonstrated that in adult mammalian species the pineal neurons contained some neuropeptides and neurotransmitters such as leu-enkephalin, met-enkephalin, substance-P, somatostatin and γ-aminobutiric acid. Oxytocin, vasopressin mRNAs and peptides were also demonstrated. No data are available on the chemical nature of the neurons in perinatal rats. In the present experiment we used immunohistochemistry to clarify this issue. After paraformaldehyde fixation frozen sections were prepared and stained for immunoreactivities of several neuropeptides and neurotransmitters. Dopamine ß-hydroxylase, neuropeptide-Y, vesicular acetylcholine transporter, vesicular glutamate transporter and calcitonin gene-related peptide antibodies were able to stain fibers. According to previous data these fibers may be sympathetic, parasympathetic or sensory. Vesicular glutamate transporter antibody may stain pinealocytes as well. Some cells were immunoreactive for substance-P, oxytocin, vasopressin, leu-enkefalin and glutamic acid decarboxylase. These immnoreactivities showed colocalization with neuron-specific nuclear protein immunoreactivity indicating that these cells were neurons. Calbindin was observed in oval and elongated cells resembling pinealocytes. Based on the results obtained in adult mammals, the pineal neurons may be analogue to retinal ganglion cells, or they may function as interneurons in the retino-pinealo-retinal neuronal circuit or peptidergic neurons may influence pinealocytes in a paracrine manner.
Subject(s)
Neurons/cytology , Neuropeptides/analysis , Neurotransmitter Agents/analysis , Pineal Gland/chemistry , Pineal Gland/cytology , Animals , Animals, Newborn , Female , Male , Neurons/metabolism , Pineal Gland/metabolism , RatsABSTRACT
It is well established that the adult mammalian pineal body (PB), with the exception of rodents, contains nerve cell bodies. Based on our previous results we have proposed that there is a pinealo-to-retinal neuronal connection in adult hamsters and in prebubertal rats. By the time the animals reached puberty, labeled cells in the PB were not observed in rats. In the present experiment, we provide light and electron microscopic immunohistochemical evidence that the labeled cells in the PB of prepubertal rats are neurons. Pinealocytes cannot transport neurotropic viruses. Virus labeled cells do not show S-antigen immunoreactivity typical for pinealocytes of six-day-old rats. Electron microscopic investigation confirmed the neuronal nature of virus labeled cells. These neurons, similarly to that of hamsters, also establish pinealo-to-retinal connections in prepubertal rats.
Subject(s)
Herpesvirus 1, Suid/metabolism , Pineal Gland/chemistry , Pineal Gland/metabolism , Retinal Neurons/chemistry , Retinal Neurons/metabolism , Sexual Maturation/physiology , Animals , Animals, Newborn , Biological Transport/physiology , Immunohistochemistry , Male , Microscopy/methods , Microscopy, Electron/methods , Pineal Gland/ultrastructure , Rats , Rats, Wistar , Retinal Neurons/ultrastructureABSTRACT
Cocaine- and amphetamine-regulated transcript (CART) peptides have been implicated in spinal pain transmission. A dense plexus of CART-immunoreactive fibres has been described in the superficial laminae of the spinal cord, which are key areas in sensory information and pain processing. We demonstrated previously that the majority of these fibres originate from nociceptive primary afferents. Using tract tracing, multiple immunofluorescent labelling and electronmicroscopy we determined the proportion of peptidergic primary afferents expressing CART, looked for evidence for coexistence of CART with galanin in these afferents in lamina I and examined their targets. Almost all (97.9%) randomly selected calcitonin gene-related peptide (CGRP)-immunoreactive terminals were substance P (SP)-positive (+) and CART was detected in approximately half (48.6%) of them. Most (81.4%) of the CGRP/SPergic boutons were galanin+ and approximately half (49.0%) of these contained CART. Many (72.9%) of the CARTergic boutons which expressed CGRP were also immunoreactive for galanin, while only 8.6% of the CARTergic terminals were galanin+ without CGRP. Electron microscopy showed that most of the CART terminals formed asymmetrical synapses, mainly with dendrites. All different morphological and neurochemical subtypes of spinoparabrachial projection neurons in the lamina I received contacts from CART-immunoreactive nociceptive afferents. The innervation density from these boutons did not differ significantly between either the different neurochemical or the morphological subclasses of these cells. This suggests a nonselective innervation of lamina I projection neurons from a subpopulation of CGRP/SP afferents containing CART peptide. These results provide anatomical evidence for involvement of CART peptide in spinal pain transmission.
Subject(s)
Afferent Pathways/metabolism , Nerve Tissue Proteins/metabolism , Nociceptors/metabolism , Pain/metabolism , Posterior Horn Cells/metabolism , Spinal Nerve Roots/metabolism , Afferent Pathways/ultrastructure , Animals , Calcitonin Gene-Related Peptide/metabolism , Dendrites/metabolism , Dendrites/ultrastructure , Galanin/metabolism , Immunohistochemistry , Male , Microscopy, Electron, Transmission , Nociceptors/ultrastructure , Pain/physiopathology , Posterior Horn Cells/ultrastructure , Presynaptic Terminals/metabolism , Presynaptic Terminals/ultrastructure , Rats , Rats, Wistar , Spinal Nerve Roots/ultrastructure , Substance P/metabolismABSTRACT
Dipeptidyl-peptidase 4 (DPP4) enzyme is involved in the degradation of many biologically active peptides including opioids. Its role in pain transmission is poorly elucidated. Recently we reported on the spinal antihyperalgesic effects of DPP4 inhibitors, Ile-Pro-Ile (Diprotin A) and vildagliptin in carrageenan-evoked acute inflammatory pain in rats. The present study investigated the effects of intrathecal (it.) diprotin A and vildagliptin in Complete Freund's Adjuvant- (CFA) and formalin induced pain in rats. The former assay can model the subchronic inflammatory pain condition and the later one reflects both acute tonic and inflammatory pain conditions. The involvement of opioid receptor (OR) subtypes, Y1-, and GLP1 receptors were also investigated. In CFA pain model it. diprotin A or vildagliptin dose-dependently inhibits hyperalgesia in ipsilateral while has no effect in contralateral paws. The peak effect was achieved 30 min following drug administration which was used for further analysis. Both compounds showed naltrexone reversible antihyperalgesia. Co-administration of OR-subtype-selective antagonists with diprotin A and vildagliptin revealed involvement of µ and δ > µ opioid receptors, respectively. Co-administered Y1 but not GLP1 receptor antagonists reversed the antihyperalgesic action of both DPP4 inhibitors. In touch-hypersensitivity both compounds were ineffective. In formalin test only diprotin A showed µ and δ OR-mediated antinociception and only in the 2nd phase. This effect was Y1 or GLP-1 receptor antagonist insensitive. In conclusion, diprotin A and vildagliptin display antinociception of different mechanisms of action in subchronic inflammatory pain. Furthermore, the spinal pain relay points of inflammatory pain of acute or subchronic conditions were more effectively affected by diprotin A than vildagliptin which needs future elucidation.
Subject(s)
Oligopeptides/pharmacology , Pain/drug therapy , Vildagliptin/pharmacology , Analgesics/pharmacology , Analgesics, Opioid/pharmacology , Animals , Dipeptidyl-Peptidase IV Inhibitors/metabolism , Dipeptidyl-Peptidase IV Inhibitors/pharmacology , Hyperalgesia/metabolism , Inflammation/drug therapy , Inflammation/metabolism , Male , Narcotic Antagonists/pharmacology , Oligopeptides/metabolism , Pain/physiopathology , Pain Measurement , Rats , Rats, Wistar , Receptors, Opioid/metabolism , Receptors, Opioid, mu , Vildagliptin/metabolismABSTRACT
It was accepted for a long time that in mammals there is only retinofugal neuronal connection between the eye and the pineal body (PB). In our previous paper we described that nerve cells were present in hamster PB and these neurons could establish a reverse connection with the retina through a transsynaptic pathway. In adult albino rats neuronal perikarya were not found. In this present experiment it was examined whether the lack of these nerve cells in the PB of adult rats is the result of an apoptotic phenomenon or the lack of migration during the fetal period. Green fluorescence protein expressing pseudorabies virus, spreading only in retrograde direction, was injected into the vitreous body of rats at various postnatal ages. Virus labeled cell bodies were not observed in the PB of adult rats; however, labeling with gradually decreasing number of cells was present in animals aged 3-6, 13-14, 20, 35 and 41 postnatal days. Injection of virus, spreading in anterograde direction (expressing red fluorescence protein), into the PB of young prepubertal animals resulted in labeling in the retina. This observation indicates that the pinealo-retinal connection in prepubertal period is active. Immunostaining revealed that some of the labeled neuronal perikarya showed activated caspase-3 (an apoptotic marker) immunoreactivity. Our results clearly show that the neurons migrate to the PB and later, during the prepubertal period, they disappear. Caspase-3 immnoreactivity indicates that these cells die off by apoptosis.
Subject(s)
Herpesvirus 1, Suid/pathogenicity , Retina/virology , Retinal Neurons/virology , Visual Pathways/virology , Animals , Male , Pineal Gland/virology , Rats, Sprague-Dawley , Retina/metabolism , Suprachiasmatic Nucleus/virology , Synapses/physiologyABSTRACT
Altered pain sensations such as hyperalgesia and allodynia are characteristic features of various pain states, and remain difficult to treat. We have shown previously that spinal application of dipeptidyl peptidase 4 (DPP4) inhibitors induces strong antihyperalgesic effect during inflammatory pain. In this study we observed low level of DPP4 mRNA in the rat spinal dorsal horn in physiological conditions, which did not change significantly either in carrageenan-induced inflammatory or partial nerve ligation-generated neuropathic states. In naïve animals, microglia and astrocytes expressed DPP4 protein with one and two orders of magnitude higher than neurons, respectively. DPP4 significantly increased in astrocytes during inflammation and in microglia in neuropathy. Intrathecal application of two DPP4 inhibitors tripeptide isoleucin-prolin-isoleucin (IPI) and the antidiabetic drug vildagliptin resulted in robust opioid-dependent antihyperalgesic effect during inflammation, and milder but significant opioid-independent antihyperalgesic action in the neuropathic model. The opioid-mediated antihyperalgesic effect of IPI was exclusively related to mu-opioid receptors, while vildagliptin affected mainly delta-receptor activity, although mu- and kappa-receptors were also involved. None of the inhibitors influenced allodynia. Our results suggest pathology and glia-type specific changes of DPP4 activity in the spinal cord, which contribute to the development and maintenance of hyperalgesia and interact with endogenous opioid systems.
Subject(s)
Dipeptidyl Peptidase 4/genetics , Hyperalgesia/drug therapy , Inflammation/drug therapy , Neuralgia/drug therapy , Analgesics, Opioid/administration & dosage , Animals , Astrocytes/drug effects , Cell Lineage/genetics , Dipeptidyl-Peptidase IV Inhibitors/administration & dosage , Hyperalgesia/genetics , Hyperalgesia/pathology , Inflammation/genetics , Inflammation/pathology , Male , Neuralgia/genetics , Neuralgia/pathology , Neuroglia/drug effects , Rats , Rats, Sprague-Dawley , Rats, Wistar , Receptors, Opioid, kappa/genetics , Receptors, Opioid, mu , Spinal Cord/drug effects , Spinal Cord/pathologyABSTRACT
It is well established that last-order premotor interneurons in the spinal cord have crucial importance in the integration of activities generated by the spinal motor apparatus, sensory information and volleys arising from higher motor centers, indicating that they play a substantial role in spinal motor functions. Despite extensive studies, synaptic input systems of these neurons have not been investigated in detail up to now with morphological approaches. On this basis, the present experiments were aimed at the visualization of possible contacts between primary afferents and last-order premotor interneurons in the lumbar spinal cord of rats using double label neural tracing methods in light microscopy. The findings show that terminal puncta of primary afferents do establish indeed appositions on last-order premotor interneurons. From the quantitative point of view, these appositions occur, however, in limited numbers. The study also shows that last-order premotor interneurons contacted by primary afferents tend to be concentrated at the segmental level of the innervated motoneurons, and are evenly distributed along the mediolateral extent of laminae V-VI and in the dorsal portion of lamina VII.
Subject(s)
Interneurons/physiology , Nerve Fibers/physiology , Neurons, Afferent/physiology , Spinal Cord/physiology , Animals , Biotin/analogs & derivatives , Data Interpretation, Statistical , Dextrans , Fluorescent Dyes , Immunohistochemistry , Male , Rats , Rats, Wistar , Reflex, Monosynaptic/physiology , Synapses/physiologyABSTRACT
Lamina I of the spinal cord is densely innervated by nociceptive primary afferents, many of which contain substance P. It contains numerous projection neurons: the majority of these respond to noxious stimuli, however some are activated by cooling. In the rat, approximately 80% of the projection neurons express the neurokinin 1 (NK1) receptor, on which substance P acts, and most cells with this receptor are activated by noxious stimuli. Lamina I neurons can be classified morphologically into pyramidal, multipolar, and fusiform types. It has been reported in the cat that pyramidal neurons are activated only by cooling and that in monkey relatively few pyramidal cells are NK1 receptor-immunoreactive. We have used immunocytochemistry to examine the innervation of lamina I projection neurons in the rat by substance P-containing primary afferents and their responses to a noxious stimulus (subcutaneous formalin injection). NK1 receptor-immunoreactive projection cells received a significantly higher density of contacts from substance P-containing afferents than neurons that lacked the receptor. Most contacts on NK1 receptor-immunoreactive cells were associated with synapses. Formalin injection induced c-Fos in approximately 80% of projection neurons with the NK1 receptor and in 25-45% of those without it. More than 80% of pyramidal neurons expressed the receptor, and for both substance P innervation and c-Fos expression there were no significant differences among different morphological types of NK1 receptor-immunoreactive neuron. We conclude that presence or absence of the NK1 receptor is a better indicator of function than morphology for lamina I projection neurons in the rat.
Subject(s)
Neurons/cytology , Neurons/metabolism , Receptors, Neurokinin-1/biosynthesis , Spinal Cord/metabolism , Stilbamidines , Substance P/biosynthesis , Animals , Axons/ultrastructure , Calcitonin Gene-Related Peptide/biosynthesis , Cell Count , Cholera Toxin , Dendrites/ultrastructure , Fluorescent Dyes , Formaldehyde , Immunohistochemistry , Male , Microscopy, Confocal , Microscopy, Electron , Neurons/ultrastructure , Neurons, Afferent/cytology , Neurons, Afferent/metabolism , Neurons, Afferent/ultrastructure , Pain Measurement , Proto-Oncogene Proteins c-fos/biosynthesis , Pyramidal Cells/cytology , Pyramidal Cells/metabolism , Rats , Rats, Wistar , Spinal Cord/cytology , Synapses/ultrastructureABSTRACT
We have reported previously that the dipeptidyl peptidase IV inhibitor Ile-Pro-Ile had an antihyperalgesic action in rats when given intrathecally in the carrageenan-induced hyperalgesia, as detected by the Randall-Selitto test. Vildagliptin, a non-peptide inhibitor of the same enzyme, which is already on the market as an "euglycemic" agent in diabetics, has a slightly more potent and more sustained antihyperalgesic effect in the same test when given by the same route. The action of 3nmol/rat vildagliptin could be antagonized by subcutaneous naltrexone (0.5mg/kg) pretreatment, or by intrathecally co-administered specific antiserum to endomorphin-2. Thus, the antihyperalgesia by vildagliptin, similarly to Ile-Pro-Ile, was opioid receptor-mediated and could be attributed to the promotion of endomorphin-2 generation in rat spinal cord dorsal horn. Furthermore, vildagliptin (1mg/kg) is a potent antihyperalgesic also when given subcutaneously.
Subject(s)
Adamantane/analogs & derivatives , Dipeptidyl Peptidase 4/metabolism , Dipeptidyl-Peptidase IV Inhibitors/pharmacology , Hyperalgesia/drug therapy , Nitriles/pharmacology , Oligopeptides/biosynthesis , Pyrrolidines/pharmacology , Spinal Cord/drug effects , Spinal Cord/metabolism , Adamantane/administration & dosage , Adamantane/pharmacology , Adamantane/therapeutic use , Animals , Dipeptidyl-Peptidase IV Inhibitors/administration & dosage , Dipeptidyl-Peptidase IV Inhibitors/therapeutic use , Dose-Response Relationship, Drug , Hyperalgesia/metabolism , Injections, Spinal , Injections, Subcutaneous , Male , Nitriles/administration & dosage , Nitriles/therapeutic use , Pyrrolidines/administration & dosage , Pyrrolidines/therapeutic use , Rats , Rats, Wistar , Reproducibility of Results , Time Factors , VildagliptinABSTRACT
Cocaine- and amphetamine-regulated transcript peptides (CART) have been implicated in the regulation of several physiological functions, including pain transmission. A dense plexus of CART-immunoreactive fibres has been described in the superficial laminae of the spinal cord, which are key areas in sensory information and pain processing. In this study, we used antibody against CART peptide, together with markers for various types of primary afferents, interneurons and descending systems to determine the origin of the CART-immunoreactive axons in the superficial laminae of the rat spinal cord. Calcitonin gene-related peptide (CGRP), a marker for peptidergic primary afferents in the dorsal horn, was present in 72.6% and 34.8% of CART-immunoreactive axons in lamina I and II, respectively. The majority of these fibres also contained substance P (SP), while a few were somatostatin (SOM)-positive. The other subpopulation of CART-immunoreactive boutons in lamina I and II also expressed SP and/or SOM without CGRP, but contained vesicular glutamate transporter 2, which is present mainly in excitatory interneuronal terminals. Our data demonstrate that the majority of CART-immunoreactive axons in the spinal dorsal horn originate from peptidergic nociceptive primary afferents, while the rest arise from excitatory interneurons that contain SP or SOM. This strongly suggests that CART peptide can affect glutamatergic neurotransmission as well as the release and effects of SP and SOM in nociception and other sensory processes.