The involvement of TRPV1 and TRPA1 in mediating craniofacial muscle nociception and mechanical hyperalgesia was investigated in male Sprague Dawley rats. First, we confirmed the expression of TRPV1 in masseter afferents in rat trigeminal ganglia (TG), and provided new data that TRPA1 is also expressed in primary afferents innervating masticatory muscles in double-labeling immunohistochemistry experiments. We then examined whether activation of each TRP channel in the masseter muscle evokes acute nocifensive responses and leads to the development of masseter hypersensitivity to mechanical stimulation using the behavioral models that have been specifically designed and validated for the craniofacial system. Intramuscular injections with specific agonists for TRPV1 and TRPA1, capsaicin and mustard oil (MO), respectively, produced immediate nocifensive hindpaw responses followed by prolonged mechanical hyperalgesia in a concentrationdependent manner. Pretreatment of the muscle with a TRPV1 antagonist, capsazepine, effectively attenuated the capsaicin-induced muscle nociception and mechanical hyperalgesia. Similarly, pretreatment of the muscle with a selective TRPA1 antagonist, AP18, significantly blocked the MOinduced muscle nociception and mechanical hyperalgesia. We confirmed these data with another set of selective antagonist for TRPV1 and TRPA1, AMG9810 and HC030031, respectively. Collectively, these results provide compelling evidence that TRPV1 and TRPA1 can functionally contribute to muscle nociception and hyperalgesia, and suggest that TRP channels expressed in muscle afferents can engage in the development of pathologic muscle pain conditions.

TRPA1 is expressed in muscle afferents and direct activation of these receptors induces acute mechanical hypersensitivity. However, the functional role of TRPA1 under pathological muscle pain conditions and mechanisms by which TRPA1 mediate muscle pain and hyperalgesia are not clearly understood. Two rodent behavioral models validated to assess craniofacial muscle pain conditions were used to study ATP- and NMDA-induced acute mechanical hypersensitivity and complete Freund’s adjuvant (CFA)-induced persistent mechanical hypersensitivity. The rat grimace scale was utilized to assess inflammation-induced spontaneous muscle pain. Behavioral pharmacology experiments were performed to assess the effects of AP18, a selective TRPA1 antagonist under these conditions. TRPA1 expression levels in trigeminal ganglia were examined before and after CFA treatment in the rat masseter muscle. Pre-treatment of the muscle with AP18 dose-dependently blocked the development of acute mechanical hypersensitivity induced by NMDA and αβmeATP, a specific agonist for NMDA and P2X3 receptor, respectively. CFA-induced mechanical hypersensitivity and spontaneous muscle pain responses were significantly reversed by post-treatment of the muscle with AP18 when CFA effects were most prominent. CFA-induced myositis was accompanied by significant up-regulation of TRPA1 expression in TG. Our findings showed that TRPA1 in muscle afferents plays an important role in the development of acute mechanical hypersensitivity and in the maintenance of persistent muscle pain and hypersensitivity. Our data suggested that TRPA1 may serve as a downstream target of pro-nociceptive ion channels, such as P2X3 and NMDA receptors in masseter afferents, and that increased TRPA1 expression under inflammatory conditions may contribute to the maintenance of persistent muscle pain and mechanical hyperalgesisa. Mechanistic studies elucidating transcriptional or post-translational regulation of TRPA1 expression under pathological pain conditions should provide important basic information to further advance the treatment of craniofacial muscle pain conditions.

In this study, we assessed the effects of peripherally administered cannabinoids in an orofacial myositis model, and the role of sex hormones in cannabinoid receptor (CBR) expression in trigeminal ganglia (TG). Peripherally administered arachidonylcyclopropylamide (ACPA), a specific CB1R agonist, significantly attenuated complete Freund’s adjuvant (CFA)-induced mechanical hypersensitivity in the masseter muscle in male rats. The ACPA effect was blocked by a local administration of AM251, a specific CB1R antagonist, but not by AM630, a specific CB2R antagonist. In female rats, a 30-fold higher dose of ACPA was required to produce a moderate reduction in mechanical hypersensitivity. CFA injected in masseter muscle significantly upregulated CB1R mRNA expression in TG in male, but not in female, rats. There was a close correlation between the CB1R mRNA levels in TG and the antihyperalgesic effect of ACPA. Interleukin (IL)-1β and IL-6, which are elevated in the muscle tissue following CFA treatment, induced a significant upregulation of CB1R mRNA expression in TG from male rats. The upregulation of CB1R was prevented in TG cultures from orchidectomized male rats, which was restored by the application of testosterone. The cytokines did not alter the CB1R mRNA level in TG from intact as well as ovariectomized female rats. Neither estradiol supplement nor estrogen receptor blockade had any effects on CB1R expression. These data indicate that testosterone, but not estradiol, is required for the regulation of CB1Rs in TG under inflammatory conditions, which provide explanations for the sex differences in the antihyperalgesic effects of peripherally administered cannabinoids.

SummaryFunctional genomics has transformed from futuristic concept to well‐established scientific discipline during the last decade. Cotton functional genomics promise to enhance the understanding of fundamental plant biology to systematically exploit genetic resources for the improvement of cotton fibre quality and yield, as well as utilization of genetic information for germplasm improvement. However, determining the cotton gene functions is a much more challenging task, which has not progressed at a rapid pace. This article presents a comprehensive overview of the recent tools and resources available with the major advances in cotton functional genomics to develop elite cotton genotypes. This effort ultimately helps to filter a subset of genes that can be used to assemble a final list of candidate genes that could be employed in future novel cotton breeding programme. We argue that next stage of cotton functional genomics requires the draft genomes refinement, re‐sequencing broad diversity panels with the development of high‐throughput functional genomics tools and integrating multidisciplinary approaches in upcoming cotton improvement programmes.

In this study, we investigated age and sex differences in acute and chronic pain in rats. Groups of young (3–6 months) and aged (20–24 months) male and female Fischer 344 rats were used to assess basal thermal and mechanical thresholds, capsaicin-induced acute nocifensive responses and c-Fos expression in the spinal cord, and monoiodoacetate (MIA)-induced knee osteoarthritis (OA)-like pain responses. There was a significant sex, but not age, effect on thermal threshold on the hindpaw and mechanical threshold on the knee joint. No significant age and sex differences in capsaicin-induced nocifensive and c-Fos responses were observed. MIA induced a greater peak reduction of weight-bearing responses in aged males than young rats. Aged females developed the most profound weight-bearing deficit. With knee joint sensitivity as a primary outcome measure, MIA induced more pronounced and longer-lasting hyperalgesia in older rats, with aged female rats showing the worst effect. These data suggest that age may not have significant effect on acute nociceptive processing, but it significantly impacts OA-like pain, making aged rats, especially females, more vulnerable to chronic pain conditions. These preclinical models should provide important tools to investigate basic mechanisms underlying the impact of age and sex in chronic pain conditions.

Long noncoding RNAs (lncRNAs) play important roles in various biological regulatory processes in yeast, mammals, and plants. However, no systematic identification of lncRNAs has been reported in Gossypium arboreum. In this study, the strand-specific RNA sequencing (ssRNA-seq) of samples from cotton fibers and leaves was performed, and lncRNAs involved in fiber initiation and elongation processes were systematically identified and analyzed. We identified 5,996 lncRNAs, of which 3,510 and 2,486 can be classified as long intergenic noncoding RNAs (lincRNAs) and natural antisense transcripts (lncNAT), respectively. LincRNAs and lncNATs are similar in many aspects, but have some differences in exon number, exon length, and transcript length. Expression analysis revealed that 51.9% of lincRNAs and 54.5% of lncNATs transcripts were preferentially expressed at one stage of fiber development, and were significantly highly expressed than protein-coding transcripts (21.7%). During the fiber and rapid elongation stages, rapid and dynamic changes in lncRNAs may contribute to fiber development in cotton. This work describes a set of lncRNAs that are involved in fiber development. The characterization and expression analysis of lncRNAs will facilitate future studies on their roles in fiber development in cotton. long noncoding RNAs, strand specific RNA sequencing, fiber, transcriptome, expression Citation:

Sucrose synthase (Sus) is a key enzyme in plant sucrose metabolism. In cotton, Sus (EC 2.4.1.13) is the main enzyme that degrades sucrose imported into cotton fibers from the phloem of the seed coat. This study demonstrated that the genomes of Gossypium arboreum L., G. raimondii Ulbr., and G. hirsutum L., contained 8, 8, and 15 Sus genes, respectively. Their structural organizations, phylogenetic relationships, and expression profiles were characterized. Comparisons of genomic and coding sequences identified multiple introns, the number and positions of which were highly conserved between diploid and allotetraploid cotton species. Most of the phylogenetic clades contained sequences from all three species, suggesting that the Sus genes of tetraploid G. hirsutum derived from those of its diploid ancestors. One Sus group (Sus I) underwent expansion during cotton evolution. Expression analyses indicated that most Sus genes were differentially expressed in various tissues and had development-dependent expression profiles in cotton fiber cells. Members of the same orthologous group had very similar expression patterns in all three species. These results provide new insights into the evolution of the cotton Sus gene family, and insight into its members' physiological functions during fiber growth and development.

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