Complement component C1q is an immunological rheostat that regulates Fc:Fc[Formula: see text]R interactions.

Though binding sites for the complement factor C1q and the canonical fragment crystallizable (Fc) gamma receptors (Fc[Formula: see text]Rs) on immunoglobulin G (IgG) molecules overlap, how C1q decoration of immune complexes (ICs) influences their ability to engage Fc[Formula: see text]Rs remains unknown. In this report, we use recombinant human Fc multimers as stable IC mimics to show that C1q engagement of ICs directly and transiently inhibits their interactions with Fc[Formula: see text]RIII (CD16) on human natural killer (NK) cells. This inhibition occurs by C1q engagement alone as well as in concert with other serum factors. Furthermore, the inhibition of Fc[Formula: see text]RIII engagement mediated by avid binding of C1q to ICs is directly associated with IC size and dependent on the concentrations of both C1q and Fc multimers present. Functionally, C1q-mediated Fc blockade limits the ability of NK cells to induce the upregulation of the cosignaling molecule, 4-1BB (CD137), and to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Although C1q is traditionally viewed as a soluble effector molecule, we demonstrate that C1q may also take on the role of an "immunologic rheostat," buffering Fc[Formula: see text]R-mediated activation of immune cells by circulating ICs. These data define a novel role for C1q as a regulator of immune homeostasis and add to our growing understanding that complement factors mediate pleiotropic effects.

Peripheral mechanisms contribute to comorbid visceral hypersensitivity induced by preexisting orofacial pain and stress in female rats.

BACKGROUND: Stress exacerbates many chronic pain syndromes including irritable bowel syndrome (IBS). Among these patient populations, many suffer from comorbid or chronic overlapping pain conditions and are predominantly female. Nevertheless, basic studies investigating chronic psychological stress-induced changes in pain sensitivity have been mostly carried out in male rodents. Our laboratory developed a model of comorbid pain hypersensitivity (CPH) (stress in the presence of preexisting orofacial pain inducing chronic visceral pain hypersensitivity that significantly outlasts transient stress-induced pain hypersensitivity (SIH)) facilitating the study of pain associated with IBS. Since CPH and SIH are phenotypically similar until SIH resolves and CPH persists, it is unclear if underlying mechanisms are similar. METHODS: In the present study, the visceromotor response (VMR) to colorectal distention was recorded in the SIH and CPH models in intact females and ovariectomized rats plus estradiol replacement (OVx + E2). Over several months, rats were determined to be susceptible or resilient to stress and the role of peripheral corticotrophin-releasing factor (CRF) underlying in the pain hypersensitivity was examined. KEY RESULTS: Stress alone induced transient (3-4 weeks) visceral hypersensitivity, though some rats were resilient. Comorbid conditions increased susceptibility to stress prolonging hypersensitivity beyond 13 weeks. Both models had robust peripheral components; hypersensitivity was attenuated by the CRF receptor antagonist astressin and the mast cell stabilizer disodium cromoglycate (DSCG). However, DSCG was less effective in the CPH model compared to the SIH model. CONCLUSIONS AND INFERENCES: The data indicate many similarities but some differences in mechanisms contributing to comorbid pain conditions compared to transient stress-induced pain.

[Genetic analysis of a pedigree affected with congenital split-hand/foot malformation].

OBJECTIVE: To explore the genetic basis for a Chinese pedigree affected with split hand/foot malformation (SHFM). METHODS: Genomic DNA of the proband and other affected members was extracted from peripheral blood samples. Chromosomal microarray analysis was employed to detect genome-wide copy number variations (CNVs). RESULTS: A 400 kb microduplication was identified in the 10q24.31-q24.32 region among all affected individuals. The microduplication has involved four genes, namely LBX1, BTRC, POLL and DPCD, in addition with part of FBXW4 gene. CONCLUSION: The 10q24.31-q24.32 microduplication has segregated with the disease phenotype in this pedigree and probably underlay the SHFM malformation in the patients.

NK cell expression of Tim-3: First impressions matter.

Given the heightened interest in manipulation of co-signaling cascades for cancer immunotherapy, we sought to determine how/whether tumors decorated with therapeutic monoclonal antibodies (mAbs) impact the expression of co-signaling molecules on human NK cells. Stimulation of NK cells with aggregated IgG1 resulted in the upregulation of HAVCR2 - the gene encoding T-cell immunoglobulin and mucin-containing domain (Tim)-3 - known to be involved in the induction of peripheral T cell tolerance. This upregulation of HAVCR2 was recapitulated at the protein level, following NK cell stimulation by either mAb opsonized tumors, recombinant human IgG1 Fc multimer, and/or non-Fc stimuli e.g. IL-12/IL-18. The patterns of Tim-3 expression were temporally distinct from the FcR mediated induction of the co-signaling molecule, 4-1BB (CD137), with Tim-3 increases observed twenty minutes following exposure to Fc multimers and remaining at high levels for at least six hours, while increases in CD137 expression were first observed at the four-hour time point. Importantly, these Tim-3+ NK cells were functionally diverse, as evidenced by the fact that their ability to produce IFN-γ in response to an NK cell responsive tumor was strictly dependent upon the stimuli employed for Tim-3 induction. These data suggest that Tim-3 upregulation is the common end-result of NK cell activation by a variety of unique and overlapping stimuli and is not an independent marker of NK cell exhaustion. Furthermore, our observations potentially explain the diverse functionality attributed to Tim-3+ NK cells and should be considered prior to use of anti-Tim-3 inhibitory mAbs for cancer immunotherapy.

Pulsed photoinitiated fabrication of inkjet printed titanium dioxide/reduced graphene oxide nanocomposite thin films.

This work reports a new technique for scalable and low-temperature processing of nanostructured TiO2 thin films, allowing for practical manufacturing of TiO2-based devices such as perovskite solar cells at low-temperature or on flexible substrates. Dual layers of dense and mesoporous TiO2/graphitic oxide nanocomposite films are synthesized simultaneously using inkjet printing and pulsed photonic irradiation. Investigation of process parameters including precursor concentration (10-20 wt%) and exposure fluence (4.5-8.5 J cm-2) reveals control over crystalline quality, graphitic oxide phase, film thickness, dendrite density, and optical properties. Raman spectroscopy shows the E g peak, characteristic of anatase phase titania, increases in intensity with higher photonic irradiation fluence, suggesting increased crystallinity through higher fluence processing. Film thickness and dendrite density is shown to increase with precursor concentration in the printed ink. The dense base layer thickness was controlled between 20 and 80 nm. The refractive index of the films is determined by ellipsometry to be 1.92 ± 0.08 at 650 nm. Films exhibit an energy weighted optical transparency of 91.1%, in comparison to 91.3% of a thermally processed film, when in situ carbon materials were removed. Transmission and diffuse reflectance are used to determine optical band gaps of the films ranging from 2.98 to 3.38 eV in accordance with the photonic irradiation fluence and suggests tunability of TiO2 phase composition. The sheet resistance of the synthesized films is measured to be 14.54 ± 1.11 Ω/□ and 28.90 ± 2.24 Ω/□ for films as-processed and after carbon removal, respectively, which is comparable to high temperature processed TiO2 thin films. The studied electrical and optical properties of the light processed films show comparable results to traditionally processed TiO2 while offering the distinct advantages of scalable manufacturing, low-temperature processing, simultaneous bilayer fabrication, and in situ formation of removable carbon nanocomposites.

Opposing Roles of Estradiol and Testosterone on Stress-Induced Visceral Hypersensitivity in Rats.

Chronic stress produces maladaptive pain responses, manifested as alterations in pain processing and exacerbation of chronic pain conditions including irritable bowel syndrome. Female predominance, especially during reproductive years, strongly suggests a role of gonadal hormones. However, gonadal hormone modulation of stress-induced pain hypersensitivity is not well understood. In the present study, we tested the hypothesis that estradiol is pronociceptive and testosterone is antinociceptive in a model of stress-induced visceral hypersensitivity (SIVH) in rats by recording the visceromotor response to colorectal distention after a 3-day forced swim (FS) stress paradigm. FS induced visceral hypersensitivity that persisted at least 2 weeks in female, but only 2 days in male rats. Ovariectomy blocked and orchiectomy facilitated SIVH. Furthermore, estradiol injection in intact male rats increased SIVH and testosterone in intact female rats attenuated SIVH. Western blot analyses indicated estradiol increased excitatory glutamate ionotropic receptor NMDA type subunit 1 expression and decreased inhibitory metabotropic glutamate receptor 2 expression after FS in male thoracolumbar spinal cord. In addition, the presence of estradiol during stress increased spinal brain-derived neurotrophic factor (BDNF) expression independent of sex. In contrast, testosterone blocked the stress-induced increase in BDNF expression in female rats. These data suggest that estradiol facilitates and testosterone attenuates SIVH by modulating spinal excitatory and inhibitory glutamatergic receptor expression. PERSPECTIVE: SIVH is more robust in female rats. Estradiol facilitates whereas testosterone dampens the development of SIVH. This could partially explain the greater prevalence of certain chronic visceral pain conditions in women. An increase in spinal BDNF is concomitant with increased stress-induced pain. Pharmaceutical interventions targeting this molecule could provide promising alleviation of SIVH in women.

EXPRESS: Histone hyperacetylation modulates spinal type II metabotropic glutamate receptor alleviating stress-induced visceral hypersensitivity in female rats.

Stress is often a trigger to exacerbate chronic pain including visceral hypersensitivity associated with irritable bowel syndrome, a female predominant functional bowel disorder. Epigenetic mechanisms that mediate stress responses are a potential target to interfere with visceral pain. The purpose of this study was to examine the effect of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid, on visceral hypersensitivity induced by a subchronic stressor in female rats and to investigate the involvement of spinal glutamate receptors. Three daily sessions of forced swim induced visceral hypersensitivity. Intrathecal suberoylanilide hydroxamic acid prevented or reversed the stress-induced visceral hypersensitivity, increased spinal histone 3 acetylation and increased mGluR2 and mGluR3 expression. Chromatin immunoprecipitation (ChIP) analysis revealed enrichment of H3K9Ac and H3K18Ac at several promoter Grm2 and Grm3 regions. The mGluR2/3 antagonist LY341495 reversed the inhibitory effect of suberoylanilide hydroxamic acid on the stress-induced visceral hypersensitivity. In surprising contrast, stress and/or suberoylanilide hydroxamic acid had no effect on spinal NMDA receptor expression or function. These data reveal histone modification modulates mGluR2/3 expression in the spinal cord to attenuate stressinduced visceral hypersensitivity. HDAC inhibitors may provide a potential approach to relieve visceral hypersensitivity associated with irritable bowel syndrome.

Epigenetic upregulation of metabotropic glutamate receptor 2 in the spinal cord attenuates oestrogen-induced visceral hypersensitivity.

OBJECTIVE: Epigenetic mechanisms are potential targets to relieve somatic pain. However, little is known whether epigenetic regulation interferes with visceral pain. Previous studies show that oestrogen facilitates visceral pain. This study aimed to determine whether histone hyperacetylation in the spinal cord could attenuate oestrogen-facilitated visceral pain. DESIGN: The effect of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) on the magnitude of the visceromotor response (VMR) to colorectal distention was examined in ovariectomised rats with/without oestrogen replacement. An additional interaction with the metabotropic glutamate receptor 2/3 (mGluR2/3) antagonist LY341495 was tested. The levels of acetylated histone and mGluR2 mRNA and protein were analysed. The binding of acetylated H3 and oestrogen receptor α (ERα) to the GRM2 promoter was measured by chromatin immunoprecipitation coupled with qPCR. RESULTS: In ovariectomised rats, 17ß-estradiol (E2), but not safflower oil, increased the magnitude of the VMR to colorectal distention. SAHA attenuated the E2-facilitated VMR, but had no effect in safflower oil-treated rats. Subsequent spinal administration of LY341495 reversed the antinociceptive effect of SAHA in E2 rats. In addition, SAHA increased mGluR2 mRNA and protein in the spinal dorsal horn following E2, but not vehicle, treatment. In contrast, neither E2 nor SAHA alone altered mGluR2 mRNA. SAHA increased binding of H3K9ac and ERα to the same regions of the GRM2 promoter in E2-SAHA-treated animals. CONCLUSIONS: Histone hyperacetylation in the spinal cord attenuates the pronociceptive effects of oestrogen on visceral sensitivity, suggesting that epigenetic regulation may be a potential approach to relieve visceral pain.

A clinically relevant animal model of temporomandibular disorder and irritable bowel syndrome comorbidity.

UNLABELLED: Temporomandibular disorder and irritable bowel syndrome are comorbid functional chronic pain disorders of unknown etiology that are triggered/exacerbated by stress. Here we present baseline phenotypic characterization of a novel animal model to gain insight into the underlying mechanisms that contribute to such comorbid pain conditions. In this model, chronic visceral hypersensitivity, a defining symptom of irritable bowel syndrome, is dependent on 3 factors: estradiol, existing chronic somatic pain, and stress. In ovariectomized rats, estradiol replacement followed by craniofacial muscle injury and stress induced visceral hypersensitivity that persisted for months. Omission of any 1 factor resulted in a transient (1 week) visceral hypersensitivity from stress alone or no hypersensitivity (no inflammation or estradiol). Maintenance of visceral hypersensitivity was estradiol dependent, resolving when estradiol replacement ceased. Referred cutaneous hypersensitivity was concurrent with visceral hypersensitivity. Increased spinal Fos expression suggests induction of central sensitization. These data demonstrate the development and maintenance of visceral hypersensitivity in estradiol-replaced animals following distal somatic injury and stress that mimics some characteristics reported in patients with temporomandibular disorder and comorbid irritable bowel syndrome. This new animal model is a powerful experimental tool that can be employed to gain further mechanistic insight into overlapping pain conditions. PERSPECTIVE: The majority of patients with temporomandibular disorder report symptoms consistent with irritable bowel syndrome. Stress and female prevalence are common to both conditions. In a new experimental paradigm in ovariectomized rats with estradiol replacement, masseter inflammation followed by stress induces visceral hypersensitivity that persists for months, modeling these comorbid pain conditions.

Sex differences and hormonal modulation of deep tissue pain.

Women disproportionately suffer from many deep tissue pain conditions. Experimental studies show that women have lower pain thresholds, higher pain ratings and less tolerance to a range of painful stimuli. Most clinical and epidemiological reports suggest female gonadal hormones modulate pain for some, but not all, conditions. Similarly, animal studies support greater nociceptive sensitivity in females in many deep tissue pain models. Gonadal hormones modulate responses in primary afferents, dorsal horn neurons and supraspinal sites, but the direction of modulation is variable. This review will examine sex differences in deep tissue pain in humans and animals focusing on the role of gonadal hormones (mainly estradiol) as an underlying component of the modulation of pain sensitivity.

Sex differences in spinal processing of transient and inflammatory colorectal stimuli in the rat.

Sex differences in the spinal processing of somatic and visceral stimuli contribute to greater female sensitivity in many pain disorders. The present study examined spinal mechanisms that contribute to sex differences in visceral sensitivity. The visceromotor response to colorectal distention (CRD) was more robust in normal female rats and after intracolonic mustard oil compared with that in male rats. No sex difference was observed in the CRD-evoked response of lumbosacral (LS) and thoracolumbar (TL) colonic afferents in normal and mustard oil-treated rats, but there was a sex difference in spontaneous activity that was exacerbated by intracolonic mustard oil. The response of visceroceptive dorsal horn neurons to CRD was greater in normal female rats in the LS and TL spinal segments. The effect of intracolonic mustard oil on the CRD-evoked response of different phenotypes of visceroceptive dorsal horn neurons was dependent on sex and segment. The NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (APV) dose-dependently attenuated the visceromotor response in normal rats with greater effect in male rats. Correspondingly, there was greater cell membrane expression of the GluN1 subunit in dorsal horn extracts in female rats. After intracolonic mustard oil, there was no longer a sex difference in the effect of APV nor GluN1 expression in LS segments, but greater female expression in TL segments. These data document a sex difference in spinal processing of nociceptive visceral stimuli from the normal and inflamed colon. Differences in dorsal horn neuronal activity and NMDA receptor expression contribute to the sex differences in the visceral sensitivity observed in awake rats.

Estrogen receptor ß activation is antinociceptive in a model of visceral pain in the rat.

UNLABELLED: The mechanism underlying estrogen modulation of visceral pain remains unclear. Our previous studies indicate that activation of estrogen receptor α (ERα) enhances visceral pain. The purpose of the present study was to investigate the role of estrogen receptor ß (ERß) activation in spinal processing of visceral stimuli. The effects of selective ERß agonists on the visceromotor response (VMR) and dorsal horn neuronal responses to colorectal distention (CRD) were tested in ovariectomized and intact female rats. The magnitude of the VMR to CRD was significantly attenuated by ERß agonists diarylpropionitrile (DPN) and WAY-200070 4 hours after subcutaneous injection. Pretreatment with the estrogen receptor antagonist ICI 182,780 obscured the DPN-evoked attenuation. There was no effect of DPN on the VMR at earlier time points. Subcutaneous and spinal administration of DPN attenuated the response of visceroceptive dorsal horn neurons with a comparable time course. DPN attenuated the VMR in intact rats regardless of estrous cycle stage. The time course of effect of ERß activation on the visceromotor response and neuronal activity is consistent with transcriptional or translational modulation of neuronal activity. PERSPECTIVE: Activation of ERß is antinociceptive in the colorectal distention model of visceral pain, which may provide a therapeutic target to manage irritable bowel syndrome in the clinic.

Spinal estrogen receptor alpha mediates estradiol-induced pronociception in a visceral pain model in the rat.

We previously reported that 17ß-estradiol (E2) is pronociceptive in a visceral pain model in the rat. Subcutaneously (s.c.) administered E2 reversed the decrease in the colorectal distention (CRD)-evoked visceromotor response produced by ovariectomy (OVx) and CRD-induced nociceptive responses were greater in proestrous rats compared with met/diestrous rats. The site of action, the type of estrogen receptors activated, and the possible intracellular signaling pathway involved are yet to be established. In the present study, intrathecal (i.t.) E2 administered to OVx rats mimicked the effects of s.c. E2, suggesting that spinal estrogen receptors are involved. This is further supported by the observations that the anti-estrogen ICI 182,780 injected i.t. in intact female rats significantly decreased the visceromotor response to CRD, the response of colonic afferents was not affected by OVx, and colonic afferents did not label for estrogen receptor α (ERα). The ERα selective agonist, 4,4',4''-[4-propyl-(1H)-pyrazole-1,3,5-triyl]tris-phenol (PPT; s.c. or i.t.) facilitated the visceromotor response similar to E2, suggesting ERα activation is involved in mediating the pronociceptive effect of E2. PPT (s.c. or i.t.) increased the response of spinal dorsal horn neurons to CRD, indicating a spinal site of action. In addition, s.c. E2 or PPT increased CRD-induced spinal extracellular signal-regulated kinase (ERK) phosphorylation that was not observed in OVx rats and a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor blocked facilitation of the visceromotor response by PPT. Taken together, the present study demonstrates that spinal ERα mediates the pronociceptive effect of E2 on visceral signal processing through activation of the MAPK pathway.

A rat model of chronic postinflammatory visceral pain induced by deoxycholic acid.

BACKGROUND & AIMS: Chronic visceral hyperalgesia is considered an important pathophysiologic symptom in irritable bowel syndrome (IBS); previous gastrointestinal inflammation is a potent etiologic factor for developing IBS. Although there are several animal models of adult visceral hypersensitivity after neonatal perturbation or acute colonic irritation/inflammation, current models of postinflammatory chronic visceral hyperalgesia are unsatisfactory. The aim of this study was to establish a model of chronic visceral hyperalgesia after colonic inflammation in the rat. METHODS: Deoxycholic acid (DCA) was instilled into the rat colon daily for 3 days and animals were tested for up to 4 weeks. RESULTS: DCA induced mild, transient colonic inflammation within 3 days that resolved within 3 weeks. An exaggerated visceromotor response, referred pain to mechanical stimulation, increased spinal Fos expression, and colonic afferent and dorsal horn neuron activity were apparent by 1 week and persisted for at least 4 weeks, indicating chronic dorsal horn hyperexcitability and visceral hyperalgesia. There was no spontaneous pain, based on open field behavior. There was a significant increase in opioid-receptor activity. CONCLUSIONS: DCA induces mild, transient colitis, resulting in persistent visceral hyperalgesia and referred pain in rats, modeling some aspects of postinflammatory IBS.

Estrogen alters spinal NMDA receptor activity via a PKA signaling pathway in a visceral pain model in the rat.

Pain symptoms in several chronic pain disorders in women, including irritable bowel syndrome, fluctuate with the menstrual cycle suggesting a gonadal hormone component. In female rats, estrogens modulate visceral sensitivity although the underlying mechanism(s) are unknown. In the present study the effects of 17-beta estradiol on N-methyl-D-aspartate (NMDA) receptor signaling of colorectal nociceptive processing in the spinal cord were examined. Estrogen receptor alpha and the NR1 subunit of the NMDA receptor are co-expressed in dorsal horn neurons, supporting a direct action of estradiol on NMDA receptors. Intrathecal administration of the NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (APV) dose-dependently attenuated the visceromotor response with greater potency in ovariectomized (OVx) rats compared to OVx with estradiol replacement (E2) rats. Estradiol significantly increased protein expression of NR1 in the lumbosacral spinal cord compared to OVx rats. Colorectal distention significantly increased phosphorylation of NR1ser-897, a PKA phosphorylation site on the NR1 subunit in E2, but not OVx rats. Intrathecal administration of a PKA inhibitor significantly attenuated the visceromotor response, decreased NR1 phosphorylation and increased the potency of APV to attenuate the visceromotor response compared to vehicle-treated E2 rats. These data suggest that estradiol increases spinal processing of visceral nociception by increasing NMDA receptor NR1 subunit expression and increasing site-specific receptor phosphorylation on the NR1 subunit contributing to an increase in NMDA receptor activity.

Estrogen modulation of morphine analgesia of visceral pain in female rats is supraspinally and peripherally mediated.

UNLABELLED: We have recently reported a sex difference in morphine-induced analgesia in a visceral pain model. To test the hypothesis that estrogen plays a role in mediating this sex difference, the effect of morphine on the visceromotor response (vmr) to colorectal distention was compared between ovariectomized (OVx) and OVx with estrogen replacement (E2) rats. After demonstrating that estrogen attenuates the potency of systemically administered morphine, we tested peripheral, spinal, and supraspinal sites for estrogen modulation of micro-opioid receptor (MOR) activity. The peripheral MOR antagonist naloxone methiodide reversed the effect of systemic morphine. The peripheral MOR agonist loperamide also attenuated the vmr and in addition was more potent in OVx rats than E2 rats, demonstrating estrogen modulation of peripheral micro-opioid analgesia. Intrathecally injected morphine attenuated the vmr, with no difference in potency noted between the 2 groups. Morphine given by intracerebroventricular injection was more potent in OVx rats than in E2 rats, suggesting estrogen modulation of supraspinal micro-opioid receptors. Results from all administration routes revealed that the potency of morphine in OVx and E2 rats was similar to male and intact female rats, respectively, suggesting that estrogen is one of the key factors contributing to the sex difference in micro-opioid analgesia. PERSPECTIVE: Female rats are less sensitive to morphine analgesia of visceral pain than male rats. This study demonstrates that estrogen decreases the analgesic potency of peripheral and supraspinal but not spinal morphine in a model of visceral pain and may be a key factor contributing to the sex difference in micro-opioid analgesia.

Sex differences in morphine-induced analgesia of visceral pain are supraspinally and peripherally mediated.

Increasing evidence suggests there is a sex difference in opioid analgesia of pain arising from somatic tissue. However, the existence of a sex difference in visceral pain and opioid analgesia is unclear. This was examined in the colorectal distention (CRD) model of visceral pain in the current study. The visceromotor response (vmr) to noxious CRD was recorded in gonadally intact male and female rats. Subcutaneous injection of morphine dose-dependently decreased the vmr in both groups without affecting colonic compliance. However, morphine was significantly more potent in male rats than females. Because systemic morphine can act at peripheral tissue and in the central nervous system (CNS), the source of the sex difference in morphine analgesia was determined. The peripherally restricted mu-opioid receptor (MOR) antagonist naloxone methiodide dose-dependently attenuated the effects of systemic morphine. Systemic administration of the peripherally restricted MOR agonist loperamide confirmed peripherally mediated morphine analgesia and revealed greater potency in males compared with females. Spinal administration of morphine dose-dependently attenuated the vmr, but there was no sex difference. Intracerebroventricular administration of morphine also dose-dependently attenuated the vmr with significantly greater potency in male rats. The present study documents a sex difference in morphine analgesia of visceral pain that is both peripherally and supraspinally mediated.

Modulatory effects of estrogen and progesterone on colorectal hyperalgesia in the rat.

The contribution of estrogen and progesterone to colorectal hyperalgesia was examined in female rats. The electromyogram recorded from the abdominal wall (visceromotor response, vmr) and the discharge of lumbosacral dorsal horn neurons to colorectal distention (CRD) were measured in intact female, ovariectomized (OVx) and estradiol replaced OVx (E2; 50mug, 48h) rats with and without colonic inflammation. Colorectal hyperalgesia was transient in intact rats, but persisted at least 4h in E2 and OVx rats. The magnitude of hyperalgesia in E2 rats was greater than OVx which was greater than intact rats. Dorsal horn neurons that responded to CRD with an Abrupt (on and off with stimulus) excitatory discharge showed similar sensitivity to estradiol as the vmr following colonic inflammation. In contrast, inflammation did not increase the magnitude of response of excitatory neurons with sustained afterdischarges in any of the treatment groups. Intact female rats have a comparable plasma estrogen concentration to E2 rats, suggesting the difference in responses may have been due to antinociceptive effects of progesterone. This was tested by administering E2+/- progesterone (1mg) and measuring the vmr. Progesterone reduced the facilitation of the vmr produced by E2 before and following colonic inflammation. The present study suggests that estrogen replacement enhances visceral signal processing following colonic inflammation. Furthermore, progesterone may counteract the effects of estrogen on colorectal sensitivity.

Neonatal hind paw injury alters processing of visceral and somatic nociceptive stimuli in the adult rat.

UNLABELLED: Tissue damage during the first few weeks after birth can have profound effects on sensory processing in the adult. We have recently reported that a short-lasting inflammation of the neonatal rat hind paw produces baseline hypoalgesia and exacerbated hyperalgesia after reinflammation of that hind paw in the adult. Because the contralateral hind paw and forepaws also displayed hypoalgesia, we speculated that effects of the initial injury were not somatotopically restricted and would alter visceral sensory processing as well. In the present study we tested this hypothesis by examining the effects of neonatal hind paw injury at P3 or P14 on visceral and somatic sensitivity in the adult rat. In P3 rats, the visceromotor response evoked by colorectal distention in the absence of colonic inflammation was attenuated in carrageenan-treated neonatal rats compared to naive rats. Colonic inflammation in the adult reversed this hypoalgesia and evoked a level of visceral hyperalgesia similar to naive rats. There were no consequences of the P14 injury observed in the adult. In a second experiment, colonic inflammation in naive rats induced viscerosomatic inhibition to thermal stimulation of the forepaw and hind paw. This inhibition was reversed, and the paw withdrawal latency was slightly decreased in neonatal (P3) carrageenan-treated rats. Rats treated on P14 appeared similar to naive rats. These data support the hypothesis that neonatal hind paw injury during a critical period permanently alters sensory processing of multiple sensory modalities in the adult. Animals develop with greater inhibitory processing of somatic and visceral stimuli throughout the neuraxis. However, inflammation in the adult in previously uninjured tissue reverses the hypoalgesia and evokes development of normal hyperexcitability associated with tissue injury. PERSPECTIVE: Trauma experienced by premature infants can lead to alterations in sensory processing throughout life. This study shows that short-term somatic tissue injury to neonatal rats during a well-defined critical period alters several aspects of viscerosensory processing in the adult, demonstrating that injury to one tissue affects sensory processing throughout the body.

Electrophysiological and pharmacological properties of nucleus basalis magnocellularis neurons in rats.

AIM: To investigate the primary electrophysiological and pharmacological properties of the nucleus basalis magnocellularis (nbM) neurons. METHODS: Single unit extracellular recordings from the nbM neurons were obtained with glass micropipettes in urethane-anesthetized rats. RESULTS: Most nbM neurons responded to noxious but not innocuous mechanical, thermal, chemical, and electrical stimuli. The receptive fields were usually very large and bilateral. Electrical stimulation applied to the frontal cortex (FCX) either activated orthodromically or antidromically the nbM neurons. The FCX stimulation-induced excitatory response in the nbM neurons could be partly blocked by intracerebroventricular (icv) injection of atropine 2.5 mmol/L or tubocurarine 0.1 mmol/L. Icv injection of ach (1, 10, and 100 mmol/L) dose-dependently increased the spontaneous firing rate in most of the nbM neurons. Atropine (2.5, 25, and 250 mmol/L) or tubocurarine (0.1, 1, and 10 mmol/L) not only antagonized the ACh-induced excitation, but also inhibited the spontaneous firing of the nbM neurons. CONCLUSION: The nbM might be involved in nociception, although it was considered to play a critical role in cognitive function. Also, the nbM appears to be rich in cholinergic autoreceptors.