Guilherme de Araújo Lucas

Differential expression of microRNAs in mouse pain models

BackgroundMicroRNAs (miRNAs) are short non-coding RNAs that inhibit translation of target genes by binding to their mRNAs. The expression of numerous brain-specific miRNAs with a high degree of temporal and spatial specificity suggests that miRNAs play an important role in gene regulation in health and disease. Here we investigate the time course gene expression profile of miR-1, -16, and -206 in mouse dorsal root ganglion (DRG), and spinal cord dorsal horn under inflammatory and neuropathic pain conditions as well as following acute noxious stimulation.ResultsQuantitative real-time polymerase chain reaction analyses showed that the mature form of miR-1, -16 and -206, is expressed in DRG and the dorsal horn of the spinal cord. Moreover, CFA-induced inflammation significantly reduced miRs-1 and -16 expression in DRG whereas miR-206 was downregulated in a time dependent manner. Conversely, in the spinal dorsal horn all three miRNAs monitored were upregulated. After sciatic nerve partial ligation, miR-1 and -206 were downregulated in DRG with no change in the spinal dorsal horn. On the other hand, axotomy increases the relative expression of miR-1, -16, and 206 in a time-dependent fashion while in the dorsal horn there was a significant downregulation of miR-1. Acute noxious stimulation with capsaicin also increased the expression of miR-1 and -16 in DRG cells but, on the other hand, in the spinal dorsal horn only a high dose of capsaicin was able to downregulate miR-206 expression.ConclusionsOur results indicate that miRNAs may participate in the regulatory mechanisms of genes associated with the pathophysiology of chronic pain as well as the nociceptive processing following acute noxious stimulation. We found substantial evidence that miRNAs are differentially regulated in DRG and the dorsal horn of the spinal cord under different pain states. Therefore, miRNA expression in the nociceptive system shows not only temporal and spatial specificity but is also stimulus-dependent.

Differential regulation of TRP channels in a rat model of neuropathic pain.

ABSTRACT Neuropathic pain is a chronic disease resulting from dysfunction of the nervous system often due to peripheral nerve injury. Hypersensitivity to sensory stimuli (mechanical, thermal or chemical) is a common source of pain in patients and ion channels involved in detecting these stimuli are possible candidates for inducing and/or maintaining the pain. Transient receptor potential (TRP) channels expressed on nociceptors respond to different sensory stimuli and a few of them have been studied previously in the models of neuropathic pain. Using real‐time PCR for quantification of all known TRP channels we identified several TRP channels, which have not been associated with nociception or neuropathic pain before, to be expressed in the DRG and to be differentially regulated after spared nerve injury (SNI). Of all TRP channel members, TRPML3 showed the most dramatic change in animals exhibiting neuropathic pain behaviour compared to control animals. In situ hybridisation showed a widespread increase of expression in neurons of small, medium and large cell sizes, indicating expression in multiple subtypes. Co‐localisation of TRPML3 with CGRP, NF200 and IB4 staining confirmed a broad subtype distribution. Expression studies during development showed that TRPML3 is an embryonic channel that is induced upon nerve injury in three different nerve injury models investigated. Thus, the current results link for the first time a re‐expression of TRPML3 with the development of neuropathic pain conditions. In addition, decreased mRNA levels after SNI were seen for TRPM6, TRPM8, TRPV1, TRPA1, TRPC3, TRPC4 and TRPC5.

Exercise therapy normalizes BDNF upregulation and glial hyperactivity in a mouse model of neuropathic pain

Abstract Treatment of neuropathic pain is a clinical challenge likely because of the time-dependent changes in many neurotransmitter systems, growth factors, ionic channels, membrane receptors, transcription factors, and recruitment of different cell types. Conversely, an increasing number of reports have shown the ability of extended and regular physical exercise in alleviating neuropathic pain throughout a wide range of mechanisms. In this study, we investigate the effect of swim exercise on molecules associated with initiation and maintenance of nerve injury–induced neuropathic pain. BALB/c mice were submitted to partial ligation of the sciatic nerve followed by a 5-week aerobic exercise program. Physical training reversed mechanical hypersensitivity, which lasted for an additional 4 weeks after exercise interruption. Swim exercise normalized nerve injury–induced nerve growth factor, and brain-derived neurotrophic factor (BDNF) enhanced expression in the dorsal root ganglion, but had no effect on the glial-derived neurotrophic factor. However, only BDNF remained at low levels after exercise interruption. In addition, exercise training significantly reduced the phosphorylation status of PLC&ggr;-1, but not CREB, in the spinal cord dorsal horn in response to nerve injury. Finally, prolonged swim exercise reversed astrocyte and microglia hyperactivity in the dorsal horn after nerve lesion, which remained normalized after training cessation. Together, these results demonstrate that exercise therapy induces long-lasting analgesia through various mechanisms associated with the onset and advanced stages of neuropathy. Moreover, the data support further studies to clarify whether appropriate exercise intensity, volume, and duration can also cause long-lasting pain relief in patients with neuropathic pain.

Plasma corticosterone levels in mouse models of pain

Pain markedly activates the hypothalamic‐pituitary‐adrenal (HPA) axis and increases plasma corticosterone release interfering significantly with nociceptive behaviour as well as the mechanism of action of analgesic drugs.

Long-Term Antidepressant Treatment Inhibits Neuropathic Pain-Induced CREB and PLCγ-1 Phosphorylation in the Mouse Spinal Cord Dorsal Horn

UNLABELLED The effect of long-term administration of imipramine, a tricyclic antidepressant, on the phosphorylation status of cyclic adenosine monophosphate-responsive element-binding protein (CREB), mitogen-activated protein kinase family members, and phospholipase γ-1 (PLCγ-1) was investigated in the dorsal horn of the spinal cord following peripheral nerve lesion. Nerve injury induced an ipsilateral long-lasting increased phosphorylation of CREB and PLCγ-1 but not extracellular signal-regulated kinase (ERK1,2), p38, and c-Jun N-terminal kinase. Daily administration of imipramine (5, 10, or 30 mg/kg) for 21 days progressively reduced both tactile-induced neuropathic pain hypersensitivity and thermal hyperalgesia. After withdrawal of treatment, the antinociceptive effect of imipramine was gradually abolished but still remained for at least 3 weeks. Conversely, no analgesic effect was observed with short-term imipramine treatment. Moreover, imipramine therapy reversed nerve injury-induced CREB and PLCγ-1 phosphorylation but had no effect on ERK1,2, p38, and c-Jun N-terminal kinase activity. These results indicate that long-term administration of imipramine may prevent some of the harmful changes in the spinal cord dorsal horn following nerve injury. However, imipramine analgesic effect takes time to develop and mature, which might explain in part why the clinical analgesic effect of tricyclic antidepressants develops with a delay after the beginning of treatment. Our data also provide evidence that prolonged imipramine treatment may induce antinociception in neuropathic pain conditions because of its action on the PLCγ-1/CREB-signaling pathway. PERSPECTIVE This article demonstrates that long-term treatment with imipramine reverses some of the marked effects induced by peripheral nerve injury in the spinal dorsal horn that contribute to long-term maintenance of sensory disorder, providing a new view to the mechanisms of action of these drugs.

Estudo micro-mesoscópico das granulações aracnóides humanas

The functional anatomy of the arachnoid granulations of the upper sagittal sinus was studied by means of micromesoscopic techniques in order to contribute to elucidating aspects of drainage pathways of the cerebrospinal fluid through their fibrous components. The arrangement of fibrous elements was analysed at the base of the peduncle, peduncle, middle and apex of granulation. The analysis of seriate sections shows collagen bundles at the base of the peduncle with a predominantly circular morphology, longitudinally directed towards the peduncles longest axis. These bundles arise in the middle of the granulation, them branch off towards its apex and periphery. The elastic bundles present an arrangement similar to that described for collagen bundles, delimiting with such bundles intercommunication channels from the base of the peduncle up to the apex of the granulation. Bundles of reticular fibers arranged in between the collagen meshes were found at the base of the peduncle. The fibrous capsule of granulation is ccmposed of collagen bundles and a small number of elastic fibers.

BDNF-TRKB signaling system of the dorsal periaqueductal gray matter is implicated in the panicolytic-like effect of antidepressant drugs.

A wealth of evidence implicates the BDNF-TRKB system in the therapeutic effects of antidepressant drugs (ADs) on mood disorders. However, little is known about the involvement of this system in the panicolytic property also exerted by these compounds. In the present study we evaluated the participation of the BDNF-TRKB system of the dorsal periaqueductal gray matter (DPAG), a core structure involved in the pathophysiology of panic disorder, in AD-induced panicolytic-like effects in rats. The results showed that short- (3 days) or long-term (21 days) systemic treatment with the tricyclic ADs imipramine, clomipramine or desipramine increased BDNF levels in the DPAG. Only longterm treatment with the selective serotonin reuptake inhibitor fluoxetine was able to increase BDNF levels in this structure. After 21-day treatment, fluoxetine and the three tricyclic ADs used also increased BDNF concentration in the hippocampus, a key area implicated in their mood-related actions. Neither in the DPAG nor hippocampus did long-term treatment with the standard anxiolytics diazepam, clonazepam or buspirone affect BDNF levels. Imipramine, both after short and long-term administration, and fluoxetine under the latter regimen, raised the levels of phosphorylated TRKB in the DPAG. Short-term treatment with imipramine or BDNF microinjection inhibited escape expression in rats exposed to the elevated T maze, considered as a panicolytic-like effect. This anti-escape effect was attenuated by the intra-DPAG administration of the TRK receptor antagonist k252a. Altogether, our data suggests that facilitation of the BDNF-TRKB system in the DPAG is implicated in the panicolytic effect of ADs.

Estudo micro-mesoscópico da parede lateral do seio cavernoso humano

The authors studied the structures of human cavernous sinus in its interior as well as on the lateral wall, utilizing thick, frontal, sequential sections. They show the significance of this wall, frequently used as surgical accessway to diseases encountered within this venous structure of the dura-mater.The authors studied the structures of human cavernous sinus in its interior as well as on the lateral wall, utilizing thick, frontal, sequential sections. They show the significance of this wall, frequently used as surgical accessway to diseases encountered within this venous structure of the dura-mater.

Microscopic anatomy of the human vertebro-basilar system

Concerning the structure of connective-muscular components the authors studied the walls of the terminal segments of the vertebral arteries as well as the basilar artery, utilizing the following staining methods: Azan modified by Heidenheim, Weigerts resorcin-fuchsin, and Weigert modified by van Gieson. It was established that wall of the vertebro-basilar system exhibits a mixed structure, muscular and elastic, by means of which the vessels are adjusted to the specific blood circulation conditions. Thus, vertebral arteries show in the most external layer of tunica media an evident external elastic lamina. In contrast, in the basilar artery the elastic tissue is localized mainly in the tunica media, and is distributed heterogeneously. In its caudal segment the elastic fibers are situated in the most internal layer of tunica media, and in the cranial segment the elastic component is homogeneously distributed in the whole of tunica media.

Estudo da conectividade entre o nervo occipital maior e estruturas adjacentes considerações anátomo-clínicas

In order to offer anatomical basis that aid for clinical interpretation of headache of cervical origin a macro-mesoscopic study of greater occipital nerve and its subcutaneous rise out site was accomplished. The authors observed that in its course this nerve delineates angles and direction shifts that can stand for critical points in etiology of occipital pain, so that in its subcutaneous rise out region both occipital artery and vein shape the vasculo-nervous bundle wrapped by sheath of fibrous connective tissue which has continuity and contiguity relation with the adjoining epimysium and perimysium. From our results, anatomo-clinical aspects are discussed.In order to offer anatomical basis that aid for clinical interpretation of headache of cervical origin a macro-mesoscopic study of greater occipital nerve and its subcutaneous rise out site was accomplished. The authors observed that in its course this nerve delineates angles and direction shifts that can stand for critical points in etiology of occipital pain, so that in its subcutaneous rise out region both occipital artery and vein shape the vasculo-nervous bundle wrapped by sheath of fibrous connective tissue which has continuity and contiguity relation with the adjoining epimysium and perimysium. From our results, anatomo-clinical aspects are discussed.