Inbred mice are preferred over outbred mice because it is assumed that they display less trait variability. We compared coefficients of variation and did not find evidence of greater trait stability ...in inbred mice. We conclude that contrary to conventional wisdom, outbred mice might be better subjects for most biomedical research.
We recently demonstrated the utility of quantifying spontaneous pain in mice via the blinded coding of facial expressions. As the majority of preclinical pain research is in fact performed in the ...laboratory rat, we attempted to modify the scale for use in this species. We present herein the Rat Grimace Scale, and show its reliability, accuracy, and ability to quantify the time course of spontaneous pain in the intraplantar complete Freund's adjuvant, intraarticular kaolin-carrageenan, and laparotomy (post-operative pain) assays. The scale's ability to demonstrate the dose-dependent analgesic efficacy of morphine is also shown. In addition, we have developed software, Rodent Face Finder®, which successfully automates the most labor-intensive step in the process. Given the known mechanistic dissociations between spontaneous and evoked pain, and the primacy of the former as a clinical problem, we believe that widespread adoption of spontaneous pain measures such as the Rat Grimace Scale might lead to more successful translation of basic science findings into clinical application.
Recent failures of clinical trials of novel analgesics designed to treat neuropathic pain have led to much speculation about the underlying reasons. One often discussed possibility is that the ...placebo response in these trials has increased in recent years, leading to lower separation between the drug and placebo arms. Whether this has indeed occurred has not yet been adequately addressed. Here, we extracted data from published randomized controlled trials (RCTs) of drugs for the treatment of chronic neuropathic pain over the years 1990 to 2013. We find that placebo responses have increased considerably over this period, but drug responses have remained stable, leading to diminished treatment advantage. This trend has been driven by studies conducted in the United States. Consideration of participant and study characteristics revealed that in the United States but not elsewhere, RCTs have increased in study size and length. These changes are associated with larger placebo response. Analysis of individual RCT time courses showed different kinetics for the treatment vs placebo responses, with the former evolving more quickly than the latter and plateauing, such that maximum treatment advantage was achieved within 4 weeks.
Grimace scales quantify characteristic facial expressions associated with spontaneous pain in rodents and other mammals. However, these scales have not been widely adopted largely because of the time ...and effort required for highly trained humans to manually score the images. Convoluted neural networks were recently developed that distinguish individual humans and objects in images. Here, we trained one of these networks, the InceptionV3 convolutional neural net, with a large set of human-scored mouse images. Output consists of a binary pain/no-pain assessment and a confidence score. Our automated Mouse Grimace Scale integrates these two outputs and is highly accurate (94%) at assessing the presence of pain in mice across different experimental assays. In addition, we used a novel set of “pain” and “no pain” images to show that automated Mouse Grimace Scale scores are highly correlated with human scores (Pearson’s r = 0.75). Moreover, the automated Mouse Grimace Scale classified a greater proportion of images as “pain” following laparotomy surgery when compared to animals receiving a sham surgery or a post-surgical analgesic. Together, these findings suggest that the automated Mouse Grimace Scale can eliminate the need for tedious human scoring of images and provide an objective and rapid way to quantify spontaneous pain and pain relief in mice.
We report a novel model in which remote activation of peripheral nociceptive pathways in transgenic mice is achieved optogenetically, without any external noxious stimulus or injury. Taking advantage ...of a binary genetic approach, we selectively targeted Nav1.8(+) sensory neurons for conditional expression of channelrhodopsin-2 (ChR2) channels. Acute blue light illumination of the skin produced robust nocifensive behaviors, evoked by the remote stimulation of both peptidergic and nonpeptidergic nociceptive fibers as indicated by c-Fos labeling in laminae I and II of the dorsal horn of the spinal cord. A non-nociceptive component also contributes to the observed behaviors, as shown by c-Fos expression in lamina III of the dorsal horn and the expression of ChR2-EYFP in a subpopulation of large-diameter Nav1.8(+) dorsal root ganglion neurons. Selective activation of Nav1.8(+) afferents in vivo induced central sensitization and conditioned place aversion, thus providing a novel paradigm to investigate plasticity in the pain circuitry. Long-term potentiation was similarly evoked by light activation of the same afferents in isolated spinal cord preparations. These findings demonstrate, for the first time, the optical control of nociception and central sensitization in behaving mammals and enables selective activation of the same class of afferents in both in vivo and ex vivo preparations. Our results provide a proof-of-concept demonstration that optical dissection of the contribution of specific classes of afferents to central sensitization is possible. The high spatiotemporal precision offered by this non-invasive model will facilitate drug development and target validation for pain therapeutics.
The innate immune system is increasingly appreciated to play an important role in the mediation of chronic pain, and one molecule implicated in this process is the Toll-like receptor 4 (TLR4). Here, ...using pharmacological and genetic manipulations, we found that activating TLR4 in the spinal cord, with the agonist lipopolysaccharide (LPS), causes robust mechanical allodynia but only in male mice. Spinal LPS had no pain-producing effect in female mice. TLR4 also has a sex-specific role in inflammatory (complete Freund's adjuvant) and neuropathic (spared nerve injury) pain: pain behaviors were TLR4 dependent in males but TLR4 independent in females. The sex differences appear to be specific to the spinal cord, as LPS administered to the brain or the hindpaw produces equivalent allodynia in both sexes, and specific to pain, as intrathecal LPS produces equivalent hypothermia in both sexes. The involvement of TLR4 in pain behaviors in male mice is dependent on testosterone, as shown by gonadectomy and hormone replacement. We found no sex differences in spinal Tlr4 gene expression at baseline or after LPS, suggesting the existence of parallel spinal pain-processing circuitry in female mice not involving TLR4.
Pyraclostrobin is a strobilurin fungicide that inhibits mitochondrial complex III of fungal and mammalian cells. In toxicity studies that were used to estimate the safety factor, pyraclostrobin was ...added to animal feed or to aqueous vehicles. However, foods containing residues of pyraclostrobin and other strobilurin fungicides (azoxystrobin, trifloxystrobin, fluoxastrobin) are frequently prepared in vegetable oil prior to human consumption. The primary objective of this study was to determine if pyraclostrobin dissolved in an oil-based vehicle had adverse health outcomes in mice when compared to aqueous-based vehicles. We found that pyraclostrobin does not fully dissolve in aqueous methyl cellulose (MC) or carboxymethyl cellulose (CMC), two vehicles used in industry-sponsored toxicity studies, but does fully dissolve in corn oil. Moreover, C57BL/6 mice receiving pyraclostrobin in corn oil displayed adverse health outcomes, including loss of body weight, hypothermia and diarrhea at lower doses than when added to feed or to aqueous vehicles. Our data suggest that previous studies underestimated the true toxicity of pyraclostrobin in mammals. Additional toxicity tests using oil-based vehicles are recommended to verify current safety recommendations for strobilurin fungicides.
•Pyraclostrobin and related strobilurins have poor solubility in aqueous solutions.•Mice show adverse health outcomes at lower doses of pyraclostrobin dissolved in oil.•Previous toxicity studies using cellulose vehicles may underestimate exposure risk.
Provoked vestibulodynia, the most common form of vulvodynia (unexplained pain of the vulva), is a prevalent, idiopathic pain disorder associated with a history of recurrent candidiasis (yeast ...infections). It is characterized by vulvar allodynia (painful hypersensitivity to touch) and hyperinnervation. We tested whether repeated, localized exposure of the vulva to a common fungal pathogen can lead to the development of chronic pain. A subset of female mice subjected to recurrent Candida albicans infection developed mechanical allodynia localized to the vulva. The mice with allodynia also exhibited hyperinnervation with peptidergic nociceptor and sympathetic fibers (as indicated by increased protein gene product 9.5, calcitonin gene-related peptide, and vesicular monoamine transporter 2 immunoreactivity in the vaginal epithelium). Long-lasting behavioral allodynia in a subset of mice was also observed after a single, extended Candida infection, as well as after repeated vulvar (but not hind paw) inflammation induced with zymosan, a mixture of fungal antigens. The hypersensitivity and hyperinnervation were both present at least 3 weeks after the resolution of infection and inflammation. Our data show that infection can cause persistent pain long after its resolution and that recurrent yeast infection replicates important features of human provoked vulvodynia in the mouse.
Variability of Objectively Measured Sedentary Behavior DONALDSON, SETH C; MONTOYE, ALEXANDER H K; TUTTLE, MARY S ...
Medicine and science in sports and exercise,
2016-April, 2016-Apr, 2016-04-00, 20160401, Letnik:
48, Številka:
4
Journal Article
Recenzirano
Odprti dostop
INTRODUCTIONThe primary purpose of this study was to evaluate variability of sedentary behavior (SB) throughout a 7-d measurement period and to determine if <7 d of SB measurement would be comparable ...with the typical 7-d measurement period.
METHODSRetrospective data from Ball State University’s Clinical Exercise Physiology Laboratory on 293 participants (99 men, 55 ± 14 yr, body mass index = 29 ± 5 kg·m; 194 women, 51 ± 12 yr, body mass index = 27 ± 7 kg·m) with seven consecutive days of data collected with ActiGraph accelerometers were analyzed (ActiGraph, Fort Walton Beach, FL). Time spent in SB (either <100 counts per minute or <150 counts per minute) and breaks in SB were compared between days and by sex using a two-way repeated-measures ANOVA. Stepwise regression was performed to determine if <7 d of SB measurement were comparable with the 7-d method, using an adjusted R of ≥0.9 as a criterion for equivalence.
RESULTSThere were no differences in daily time spent in SB between the 7 d for all participants. However, there was a significant interaction between sex and days, with women spending less time in SB on both Saturdays and Sundays than men when using the 100 counts per minute cut-point. Stepwise regression showed using any 4 d would be comparable with a 7-d measurement (R > 0.90).
CONCLUSIONSWhen assessed over a 7-d measurement period, SB appears to be very stable from day to day, although there may be some small differences in time spent in SB and breaks in SB between men and women, particularly on weekend days. The stepwise regression analysis suggests that a measurement period as short as 4 d could provide comparable data (91% of variance) with a 1-wk assessment. Shorter assessment periods would reduce both researcher and subject burden in data collection.
PDF
