Peripheral pain pathways are activated by a range of stimuli. We used diphtheria toxin to kill all mouse postmitotic sensory neurons expressing the sodium channel Nav1.8. Mice showed normal motor ...activity and low-threshold mechanical and acute noxious heat responses but did not respond to noxious mechanical pressure or cold. They also showed a loss of enhanced pain responses and spontaneous pain behavior upon treatment with inflammatory insults. In contrast, nerve injury led to heightened pain sensitivity to thermal and mechanical stimuli indistinguishable from that seen with normal littermates. Pain behavior correlates well with central input from sensory neurons measured electrophysiologically in vivo. These data demonstrate that Nav1.8-expressing neurons are essential for mechanical, cold, and inflammatory pain but not for neuropathic pain or heat sensing.
Sensory acuity and motor dexterity deteriorate when human limbs cool down, but pain perception persists and cold-induced pain can become excruciating. Evolutionary pressure to enforce protective ...behaviour requires that damage-sensing neurons (nociceptors) continue to function at low temperatures. Here we show that this goal is achieved by endowing superficial endings of slowly conducting nociceptive fibres with the tetrodotoxin-resistant voltage-gated sodium channel (VGSC) Na(v)1.8 (ref. 2). This channel is essential for sustained excitability of nociceptors when the skin is cooled. We show that cooling excitable membranes progressively enhances the voltage-dependent slow inactivation of tetrodotoxin-sensitive VGSCs. In contrast, the inactivation properties of Na(v)1.8 are entirely cold-resistant. Moreover, low temperatures decrease the activation threshold of the sodium currents and increase the membrane resistance, augmenting the voltage change caused by any membrane current. Thus, in the cold, Na(v)1.8 remains available as the sole electrical impulse generator in nociceptors that transmits nociceptive information to the central nervous system. Consistent with this concept is the observation that Na(v)1.8-null mutant mice show negligible responses to noxious cold and mechanical stimulation at low temperatures. Our data present strong evidence for a specialized role of Na(v)1.8 in nociceptors as the critical molecule for the perception of cold pain and pain in the cold.
Ethanol drinking begins during adolescence and, particularly when occurs in a binge-like pattern, exerts lingering adverse consequences. Pre-clinical studies indicate that intermittent ethanol ...exposure (IEA, a model of repeated ethanol intoxication), or binge eating (BE) can increase subsequent ethanol consumption. It is unknown if the promoting effects of BE upon ethanol drinking are found in female rats and are modulated by IEA at adolescence. This study assessed interactive effects between IEA and BE, upon ethanol drinking.
Female Wistar rats were given 4.0 g/kg ethanol, every other day from postnatal day 25–45. At adulthood, they were exposed to sessions in which a brief offering of a sizeable portion of highly palatable sugary pills was followed by a 120-min exposure to an ethanol bottle.
Exploratory activity and recognition memory was not affected by the IEA. Glutathione peroxidase and catalase activity, and lipid peroxidation (measured in blood and brain at the end of the procedure) were not significantly affected by IEA or BE exposure. BE alone had a mild promoting effect on ethanol ingestion. Those rats that underwent IEA and BE, however, exhibited heightened and sustained ethanol self-administration (average of 2.12 g/kg/120 min, vs 1.15 g/kg/120 min of the other groups), that persisted throughout the BE sessions. IEA and a history of BE also promoted ethanol intake or preference in a two-bottle endpoint test.
The study suggests that exposure to IEA exerts, when followed by BE at adulthood, promoting effects upon ethanol intake, particularly at concentrations ≥ 6%.
•We measured interactions between repeated ethanol intoxication and binge eating.•Binge eating (BE) alone had a mild promoting effect on the ingestion of ethanol.•Rats given repeated ethanol intoxication and BE showed greater ethanol intake.•Recognition memory and antioxidant capacity of the rats were preserved.
Much of the research done on aging, oxidative stress, anxiety, and cognitive and social behavior in rodents has focused on caloric restriction (CR). This often involves several days of single ...housing, which can cause numerous logistical problems, as well as cognitive and social dysfunctions. Previous results in our laboratory showed the viability of long-term CR in grouped rats. Our research has studied the possibility of CR in grouped female and male littermates and unrelated CB6F1/J (C57BL/6J × BALBc/J hybrid strain) mice, measuring: (i) possible differences in body mass proportions between mice in
and CR conditions (at 70% of
), (ii) aggressive behavior, using the number of
and
as an indicator and social behavior using the
as indicator, and (iii) difference in serum adrenocorticotropic hormone (ACTH) concentrations (stress biomarker), under
and CR conditions. Results showed the impossibility of implementing CR in unrelated male mice. In all other groups, CR was possible, with a less aggressive behavior (measured only with the number of
) observed in the unrelated female mice under CR conditions. In that sense, the ACTH levels measured on the last day of CR showed no difference in stress levels. These results indicate that implementantion of long-term CR in mice can be optimized technically and also related to their well-being by grouping animals, in particular, related mice.
Obesity-induced skeletal muscle (SKM) inflexibility is closely linked to mitochondrial dysfunction. The present study aimed to evaluate the effects of melatonin on the red vastus lateralis (RVL) ...muscle in obese rat models at the molecular and morphological levels. Five-week-old male Zücker diabetic fatty (ZDF) rats and their age-matched lean littermates (ZL) were orally treated either with melatonin (10 mg/kg body weight (BW)/24 h) (M–ZDF and M–ZL) or non-treated (control) (C–ZDF and C–ZL) for 12 weeks. Western blot analysis showed that mitochondrial fission, fusion, and autophagy were altered in the C-ZDF group, accompanied by reduced SIRT1 levels. Furthermore, C-ZDF rats exhibited depleted ATP production and nitro-oxidative stress, as indicated by increased nitrites levels and reduced SOD activity. Western blotting of MyH isoforms demonstrated a significant decrease in both slow and fast oxidative fiber-specific markers expression in the C-ZDF group, concomitant with an increase in the fast glycolytic fiber markers. At the tissue level, marked fiber atrophy, less oxidative fibers, and excessive lipid deposition were noted in the C-ZDF group. Interestingly, melatonin treatment partially restored mitochondrial fission/fusion imbalance in the RVL muscle by enhancing the expression of fission (Fis1 and DRP1) markers and decreasing that of fusion (OPA1 and Mfn2) markers. It was also found to restore autophagy, as indicated by increased p62 protein level and LC3BII/I ratio. In addition, melatonin treatment increased SIRT1 protein level, mitochondrial ATP production, and SOD activity and decreased nitrites production. These effects were associated with enhanced oxidative phenotype, as evidenced by amplified oxidative fiber-specific markers expression, histochemical reaction for NADH enzyme, and muscular lipid content. In this study, we showed that melatonin might have potential therapeutic implications for obesity-induced SKM metabolic inflexibility among patients with obesity and T2DM.
Objective: To analyse changes in the range of motion (ROM) and pain after spinal manipulation of the cervical spine and thoracic spine in subjects with mechanical neck pain. Methods : Spinal ...manipulations were performed in the cervical and thoracic spine with the Gonstead and Diversified DTV techniques. To assess cervical ROM an inclinometer was used. Cervical pain was assessed by Visual Analogue Scale (VAS). The participation of 73 patients was obtained. Ages ranged from 18 to 63 years, with an average of 42.27 years. The subjects of this study were characterized by having mechanical neck pain and restricted cervical ROM. Results: We observed a reduction in the intensity of pain perceived by patients and increased cervical ROM. There were significant differences between pre-treatment values (first visit) and the fifth and tenth visits (p<0.01), and between the fifth and tenth visits (p<0.01) in all parameters except in the cervical extension of 70º. Conclusions: The results of this study suggest that spinal manipulation of the cervical and thoracic regions with the Gonstead and Diversified DTV techniques could subjectively reduce pain and produce considerable increase in cervical ROM in adults with mechanical neck pain.
Objetivos: Analizar las alteraciones en la amplitud de movimiento (ADM) y algias tras la manipulación vertebral en la columna cervical y dorsal, en sujetos con cervicalgia mecánica. Métodos: Fueron realizadas manipulaciones en la columna cervical y dorsal con las técnicas Gonstead y Diversificada DTV. Para evaluar la ADM cervical se utilizó un inclinómetro. El dolor en la columna cervical, fue evaluado mediante la Escala Visual Analógica (EVA). Se obtuvo la participación de 73 pacientes. Las edades oscilaron entre los 18 y los 63 años, con una edad promedio de 42,27 años. Los sujetos de esta investigación se caracterizaron por presentar cervicalgia mecánica y restricción en la ADM cervical. Resultados: Se observó una reducción en la intensidad del dolor percibida por los pacientes y un aumento en la ADM cervical, obteniéndose diferencias significativas entre los valores pretratamiento (primera cita) y las citas quinta y décima (p<0,01), y entre las citas quinta y décima (p<0,01) en todos los parámetros excepto en extensión cervical 70º. Conclusión: Los resultados de este estudio sugieren que la manipulación vertebral, con las técnicas Gonstead y Diversificada DTV, en la columna cervical y dorsal, podría provocar una reducción subjetiva del dolor y producir un aumento considerable en la ADM cervical en adultos con cervicalgia mecánica.
Objetivo: Analisar as alterações da amplitude de movimento (ADM) e da dor após manipulação da coluna cervical e dorsal, em indivíduos com cervicalgia mecânica. Métodos: Foram realizadas manipulações na coluna cervical e dorsal com as técnicas Gonstead e Diversificada DTV. Para avaliar a ADM cervical, utilizou-se o instrumento inclinômetro. A dor na coluna cervical foi avaliada por meio da Escala Visual Analógica (EVA). Obteve-se a participação de 73 pacientes. As idades oscilaram entre 18 e 63 anos, com média de 42,27 anos. Os indivíduos do estudo foram caracterizados por apresentar cervicalgia mecânica e restrição da ADM cervical. Resultados: Constatou-se redução da intensidade da dor percebida pelos pacientes e aumento da ADM cervical. Houve diferenças significativas entre os valores pré-tratamento (primeira consulta) e na quinta e décima consultas (p<0,01) e entre a quinta e décima consultas (p<0,01) em todos os parâmetros, exceto na extensão cervical de 70º. Conclusão: Os resultados deste estudo sugerem que a manipulação vertebral da coluna cervical e dorsal com as técnicas Gonstead e Diversificada DTV poderiam ocasionar redução subjetiva da dor e produzir aumento considerável na ADM cervical em adultos com cervicalgia mecânica.
The synthesis and pharmacological activity of a new series of 5a,7,8,8a-tetrahydro-4
,6
-pyrrolo3,4-
1,2,3triazolo1,5-
1,4oxazine derivatives as potent sigma-1 receptor (σ
R) ligands are reported. A ...lead optimization program aimed at improving the aqueous solubility of parent racemic nonpolar derivatives led to the identification of several σ
R antagonists with a good absorption, distribution, metabolism, and excretion in vitro profile, no off-target affinities, and characterized by a low basic p
(around 5) that correlates with high exposure levels in rodents. Two compounds displaying a differential brain-to-plasma ratio distribution profile,
and
, exhibited a good analgesic profile and were selected as preclinical candidates for the treatment of pain.
The synthesis and pharmacological activity of a new series of pyrazoles that led to the identification of 1-(4-(2-((1-(3,4-difluorophenyl)-1
-pyrazol-3-yl)methoxy)ethyl)piperazin-1-yl)ethanone (
, ...EST64454) as a σ
receptor (σ
R) antagonist clinical candidate for the treatment of pain are reported. The compound
is easily obtained through a five-step synthesis suitable for the production scale and shows an outstanding aqueous solubility, which together with its high permeability in Caco-2 cells will allow its classification as a BCS class I compound. It also shows high metabolic stability in all species, linked to an adequate pharmacokinetic profile in rodents, and antinociceptive properties in the capsaicin and partial sciatic nerve ligation models in mice.
Neuropathic pain may arise following peripheral nerve injury though the molecular mechanisms associated with this are unclear. We used proteomic profiling to examine changes in protein expression ...associated with the formation of hyper-excitable neuromas derived from rodent saphenous nerves. A two-dimensional difference gel electrophoresis (2D-DIGE) profiling strategy was employed to examine protein expression changes between developing neuromas and normal nerves in whole tissue lysates. We found around 200 proteins which displayed a >1.75-fold change in expression between neuroma and normal nerve and identified 55 of these proteins using mass spectrometry. We also used immunoblotting to examine the expression of low-abundance ion channels Nav1.3, Nav1.8 and calcium channel α2δ-1 subunit in this model, since they have previously been implicated in neuronal hyperexcitability associated with neuropathic pain. Finally, S35methionine in vitro labelling of neuroma and control samples was used to demonstrate local protein synthesis of neuron-specific genes. A number of cytoskeletal proteins, enzymes and proteins associated with oxidative stress were up-regulated in neuromas, whilst overall levels of voltage-gated ion channel proteins were unaffected. We conclude that altered mRNA levels reported in the somata of damaged DRG neurons do not necessarily reflect levels of altered proteins in hyper-excitable damaged nerve endings. An altered repertoire of protein expression, local protein synthesis and topological re-arrangements of ion channels may all play important roles in neuroma hyper-excitability.
The aim of this study was to evaluate the effects of serine/threonine protein phosphatase (PP) inhibitors on morphine-induced antinociception in the tail flick test in mice, and on
3Hnaloxone ...binding to the forebrain crude synaptosome fraction. Neither okadaic acid nor cantharidin (1–10
000 nM) displaced
3Hnaloxone from its specific binding sites, which indicates that they do not interact at the opioid receptor level. The i.c.v. administration of very low doses of okadaic acid (0.001–1 pg/mouse) and cantharidin (0.001–1 ng/mouse), which inhibit PP2A, produced a dose-dependent antagonism of the antinociception induced by morphine (s.c.). However,
L-nor-okadaone (0.001 pg/mouse–1 ng/mouse, i.c.v.), an analogue of okadaic acid lacking activity against protein phosphatases, did not affect the antinociceptive effect of morphine. On the other hand, high doses of okadaic acid (10 ng/mouse, i.c.v.) and cantharidin (1 μg/mouse, i.c.v.), which also block PP1, and calyculin-A (0.1 fg/mouse–1 ng/mouse, i.c.v.), which inhibits equally both PP1 and PP2A, did not modify the morphine-induced antinociception. These results suggest that the activation of type 2A serine/threonine protein phosphatases may play a role in the antinociceptive effect of morphine, and that PP1 might counterbalace this activity.
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