Improved Efficiency and Sensitivity Analysis of 3-D Agent-based Model for Pain-related Neural Activity in the Amygdala

Neuropathic pain is caused by nerve injury and involves brain areas such as the central nucleus of the amygdala (CeA). We developed the first 3-D agent-based model (ABM) of neuropathic pain-related neurons in the CeA using NetLogo3D. The execution time of a single ABM simulation using realistic parameters (e.g., 13,000 neurons and 22,000+ neural connections) is an important factor in the model’s usability. In this paper, we describe our efforts to improve the computational efficiency of our 3-D ABM, which resulted in a 28% reduction in execution time on average for a typical simulation. With this upgraded model, we performed one- and two-parameter sensitivity analyses to study the sensitivity of model output to variability in several key parameters along the anterior to posterior axis of the CeA. These results highlight the importance of computational modeling in exploring spatial and cell-type specific properties of brain regions to inform future wet lab experiments

Summer undergraduate research: A new pipeline for pain clinical practice and research

BACKGROUND: Most medical schools fail to provide adequate training of clinicians in the treatment of pain. Similarly, despite the fact that over 1/3 of Americans suffer from chronic pain, National Institutes of Health (NIH) funding for pain represents only ~1 % of the NIH budget. These issues may dissuade students from pursing pain in their clinical and research careers. To address these gaps in training and funding, we argue that exposing students to pain science early in their careers, at the undergraduate level, may be an effective method to develop a pipeline for future pain clinicians and scientists. To highlight our argument, we will describe our recent successful implementation of a cross-disciplinary and community-engaged biomedical summer research program. The Pain Undergraduate Research Experience (PURE) summer program involved both off-site and on-site experiences to expose undergraduate students to the range of careers in the pain field from basic science to clinical practice. The objective of the 10-week long PURE program was to evaluate whether a combination of basic science research, clinical practice visits, and patient interactions would increase student understanding of and exposure to the underlying science of pain. METHODS: A pre-post cohort study was used without a comparison group. Entry and exit surveys were used to evaluate students’ perceptions about pain clinical practice and research, student interest in pain, and student confidence about communicating about pain and doing basic science pain research. RESULTS: Students reported significant increases to a number of questions in the survey. Questions were scored on 5 point Likert scales and there was significant increases in student understanding of what life is like with chronic pain (2.6 vs 4.3 post survey), their confidence in explaining pain to a patient (2.8 vs 4.1) or researcher (2.8 vs 4), and their comfort with pain terminology(2.8 vs 3.9). CONCLUSIONS: With the PURE program, we wanted to entice top undergraduates to consider pain as a future area of study, practice, and/or research. We present a model that can be easily implemented at research universities throughout the United States

Alumni Voices of the African Immersion Experience

In this session, alumni shared their experiences of African immersion while they were students at UD and how that experience has carried with them in their careers and personal lives.https://ecommons.udayton.edu/global_voices_3/1009/thumbnail.jp

Marine cyanobacteria-derived serotonin receptor 2C active fraction induces psychoactive behavioral effects in mice

Context—Marine cyanobacteria offer a robust resource for natural products drug discovery due to the secondary metabolites they produce. Objective—To identify novel cyanobacterial compounds that exhibit CNS psychoactive effects. Materials and methods—Cyanobacteria were collected from Las Perlas Archipelago, Panama and subjected to dichloromethane/methanol extraction and fractionation by column chromatography before being screened for affinity against a panel of CNS targets. A 50:50 ethyl acetate:methanol fraction of one cyanobacterial extract (2064H) was subjected to HPLC and the major peak was isolated (2064H3). At a dose of 20 μg per animal, 2064H and 2064H3 were tested in mice using behavioral assays that included the forced swim, open field, and formalin tests.Context—Marine cyanobacteria offer a robust resource for natural products drug discovery due to the secondary metabolites they produce. Objective—To identify novel cyanobacterial compounds that exhibit CNS psychoactive effects. Materials and methods—Cyanobacteria were collected from Las Perlas Archipelago, Panama and subjected to dichloromethane/methanol extraction and fractionation by column chromatography before being screened for affinity against a panel of CNS targets. A 50:50 ethyl acetate:methanol fraction of one cyanobacterial extract (2064H) was subjected to HPLC and the major peak was isolated (2064H3). At a dose of 20 μg per animal, 2064H and 2064H3 were tested in mice using behavioral assays that included the forced swim, open field, and formalin tests

Activation of metabotropic glutamate receptor 5 in the amygdala modulates pain-like behavior

The central nucleus of the amygdala (CeA) has been identified as a site of nociceptive processing important for sensitization induced by peripheral injury. However, the cellular signaling components underlying this function remain unknown. Here, we identify metabotropic glutamate receptor 5 (mGluR5) as an integral component of nociceptive processing in the CeA. Pharmacological activation of mGluRs with R,S-3,5-dihydroxyphenylglycine (DHPG) in the CeA of mice is sufficient to induce peripheral hypersensitivity in the absence of injury. DHPG-induced peripheral hypersensitivity is reduced via pharmacological blockade of mGluR5 or genetic disruption of mGluR5. Further, pharmacological blockade or conditional deletion of mGluR5 in the CeA abrogates inflammation-induced hypersensitivity, demonstrating the necessity of mGluR5 in CeA-mediated pain modulation. Moreover, we demonstrate that phosphorylation of extracellular-signal regulated kinase 1/2 (ERK1/2) is downstream of mGluR5 activation in the CeA and is necessary for the full expression of peripheral inflammation-induced behavioral sensitization. Finally, we present evidence of right hemispheric lateralization of mGluR5 modulation of amygdalar nociceptive processing. We demonstrate that unilateral pharmacological activation of mGluR5 in the CeA produces distinct behavioral responses depending on whether the right or left amygdala is injected. We also demonstrate significantly higher levels of mGluR5 expression in the right amygdala compared to the left under baseline conditions, suggesting a potential mechanism for right hemispheric lateralization of amygdala function in pain processing. Taken together, these results establish an integral role for mGluR5 and ERK1/2 in nociceptive processing in the CeA

Postinflammatory hyperpigmentation after human cold pain testing

Abstract. Changes in cold temperature sensitivity are often associated with chronic pain conditions. Progress in understanding the neurobiological mechanism underlying these changes and resulting development of effective therapies has been slowed by the accessibility and affordability of devices used to measure thermal sensitivity in humans. To address this gap, we developed an inexpensive method to measure cold pain thresholds in healthy adult volunteers using dry ice and a thermode. However, early in preliminary testing, a subject presented with epidermal postinflammatory hyperpigmentation that lasted for >200 days. Although this response was unique among the small number of subjects in development of the assay, it raised questions as to the safety of the assay design

Central amygdala metabotropic glutamate receptor 5 in the modulation of visceral pain

Painful bladder syndrome is a debilitating condition that affects 3–6% of women in the United States. Multiple lines of evidence suggest that changes in central nervous system processing are key to the development of chronic bladder pain conditions, but little is known regarding the underlying cellular, molecular, and neuronal mechanisms. Using a mouse model of distension-induced bladder pain, we found that the central nucleus of the amygdala (CeA) is a critical site of neuromodulation for processing of bladder nociception. Furthermore, we demonstrate that metabotropic glutamate receptor 5 (mGluR5) activation in the CeA induces bladder pain sensitization by increasing CeA output. Thus, pharmacological activation of mGluR5 in the CeA is sufficient to increase the response to bladder distension. Additionally, pharmacological blockade or virally-mediated conditional deletion of mGluR5 in the CeA reduced responses to bladder distention suggesting that mGluR5 in the CeA is also necessary for these responses. Finally, we used optogenetic activation of the CeA and demonstrated that this caused a robust increase in the visceral pain response. The CeA localized effects on responses to bladder distention are associated with changes in extracellular signal regulated kinases 1/2 phosphorylation in the spinal cord. Overall, these data demonstrate that mGluR5 activation leads to increased CeA output that drives bladder pain sensitization

Left and right hemispheric lateralization of the amygdala in pain

Hemispheric asymmetries within the brain have been identified across taxa and have been extensively studied since the early 19th century. Here, we discuss lateralization of a brain structure, the amygdala, and how this lateralization is reshaping how we understand the role of the amygdala in pain processing. The amygdala is an almond-shaped, bilateral brain structure located within the limbic system. Historically, the amygdala was known to have a role in the processing of emotions and attaching emotional valence to memories and other experiences. The amygdala has been extensively studied in fear conditioning and affect but recently has been shown to have an important role in processing noxious information and impacting pain. The amygdala is composed of multiple nuclei; of special interest is the central nucleus of the amygdala (CeA). The CeA receives direct nociceptive inputs from the parabrachial nucleus (PBN) through the spino-parabrachio-amygdaloid pathway as well as more highly processed cortical and thalamic input via the lateral and basolateral amygdala. Although the amygdala is a bilateral brain region, most data investigating the amygdala\u27s role in pain have been generated from the right CeA, which has an overwhelmingly pro-nociceptive function across pain models. The left CeA has often been characterized to have no effect on pain modulation, a dampened pro-nociceptive function, or most recently an anti-nociceptive function. This review explores the current literature on CeA lateralization and the hemispheres\u27 respective roles in the processing and modulation of different forms of pain

Hormonal and molecular effects of restraint stress on formalin-induced pain-like behavior in male and female mice

The evolutionary advantages to the suppression of pain during a stressful event (stress-induced analgesia (SIA)) are obvious, yet the reasoning behind sex-differences in the expression of this pain reduction are not. The different ways in which males and females integrate physiological stress responses and descending pain inhibition are unclear. A potential supraspinal modulator of stress-induced analgesia is the central nucleus of the amygdala (CeA). This limbic brain region is involved in both the processing of stress and pain; the CeA is anatomically and molecularly linked to regions of the hypothalamic pituitary adrenal (HPA) axis and descending pain network. The CeA exhibits sex-based differences in response to stress and pain that may differentially induce SIA in males and females. Here, sex-based differences in behavioral and molecular indices of SIA were examined following noxious stimulation. Acute restraint stress in male and female mice was performed prior to intraplantar injections of formalin, a noxious inflammatory agent. Spontaneous pain-like behaviors were measured for 60 min following formalin injection and mechanical hypersensitivity was evaluated 120 and 180 min post-injection. Restraint stress altered formalin-induced spontaneous behaviors in male and female mice and formalin-induced mechanical hypersensitivity in male mice. To assess molecular indices of SIA, tissue samples from the CeA and blood samples were collected at the 180 min time point. Restraint stress prevented formalin-induced increases in extracellular signal regulated kinase 2 (ERK2) phosphorylation in the male CeA, but no changes associated with pERK2 were seen with formalin or restraint in females. Sex differences were also seen in plasma corticosterone concentrations 180 min post injection. These results demonstrate sex-based differences in behavioral, molecular, and hormonal indices of acute stress in mice that extend for 180 min after stress and noxious stimulation