Joel D. Greenspan - US grants

The functional properties of neurons in the superficial layers of the somatosensory cortex have received considerably less attention than those occupying the middle or deeper layers. A recent investigation focusing on the upper layers of the first somatosensory area (S-I) in cat described a class of neurons that had previously been ignored or overlooked. The proposed project will 1) examine in greater detail than has been accomplished to date, the response properties of superficial S-I neurons of the cat, and 2) determine which spinal tracts provide the various types of input to these neurons. In the first phase of the project, I will test the responsiveness of superficial S-I neurons to a wide battery of cutaneous stimuli -- mechanical and thermal, innocuous and noxious -- using both extracellular and intracellular recording techniques. Ethical considerations require that noxious stimuli only be used in the presence of a general anesthetic. For scientific validity, the agent used to produce anesthesia must not greatly alter the responsivity of the neurons under study. Thus, an initial step in the first phase of this project will be to identify anesthetic agents which would allow the study of a qualitatively unaltered neuronal population in the superficial S-I cortex. The second phase of this project involves determining the relative contributions of the various spinal tracts to the behavior of superficial S-I neurons. If an anesthetic is found that will allow investigation of the functional properties of the upper layer S-I neurons, the influences of the different input pathways will be assessed by electrically stimulating the spinal tracts while recording the responses of superficial S-I neurons. If such an anesthetic is not found, electrophysiological recordings will be made in the S-I cortex after the cat has recovered from a spinal tract lesion. Either method can indicate the spinal pathways providing input to the various types of superficial S-I neurons, and reveal the relative contributions of each pathway. The data gathered in this project could complement neuroanatomical data which indicate that the superficial layers of the somatosensory cortex have different afferent and efferent connectivity than the middle or deeper layers, as well as the more recent histochemical data showing a preferential distribution of certain neuropeptides in the superficial layers of the cerebral cortex. Elucidation of the functional properties of these neurons will extend current views of the S-I somatosensory cerebral cortex as an initial stage in the processing of inputs leading to somatic sensations.

thermoreception; pain; sensory disorders; neuroanatomy; psychophysics; heat stimulus; pleasure; brain neoplasms; stroke; thalamus; somesthetic sensory cortex; brain imaging /visualization /scanning; stimulus /response; sensory mechanism; sensory thresholds; touch; magnetic resonance imaging; human subject; electronic stimulator;

DESCRIPTION: (Adapted from the Investigator's Abstract) This project addresses issues relevant to the cerebral substrates of somesthetic perception, both in healthy human beings and those with an abnormal sensitivity to pain (allodynia and hyperalgesia). Neuroanatomical and neurophysiological studies in mammals, including human beings, have identified a number of cerebral structures that receive and process somesthetic input originating from the body, including: the post-central gyrus (primary somatosensory cortex- S1), the posterior parietal operculum (which includes the secondary somatosensory cortex - S2), the insula, and portions of the anterior cingulate cortex. These brain regions may play complementary roles for our somesthetic perceptions, including pain perception. Specifically, the S1 and S2 regions of cortex are proposed to be primarily involved with processing related to the discriminative aspects of perception, such as distinguishing the intensive or spatial features of stimulation. In contrast, the insular and anterior cingulate lesions, being anatomically related to the limbic system, are proposed to be primarily involved with the affective or emotional aspects of perception. The goal of this project is to use functional magnetic resonance imaging (fMRI) techniques and quantitative psychophysics to determine the cerebral activation patterns associated with various somatosensory stimuli, and to determine whether certain patterns of brain activation are reliably and specifically related to particular features of somesthetic experience. One specific hypothesis is that the aforementioned somatosensory cortical regions will show stimulus intensity-dependent responses for both mechanical and thermal stimuli. A second hypothesis is that the fMRI responses within S1 and S2 cortices will show better correlations with the subject's perceived intensity vs. their affective perception of thermal stimuli, and that the insular and anterior cingulate regions will show the opposite trend. Initially, these fMRI-measured cerebral response patterns will be examined in healthy individuals under normal conditions. Subsequently, we plan to follow-up this work with evaluations of individuals with allodynia and/or hyperalgesia associated with central pain. In this manner, this project will identify the cerebral response patterns to tactile, thermal, and painful stimuli, both in the neurologically normal and the chronically perturbed somatosensory system. It is anticipated that the results from this project will enhance our knowledge of how the brain processes pain-related information in humans, and of the extent to which differences in such processing occur in normal vs. pathological conditions.

DESCRIPTION (provided by applicant): This multidisciplinary SCOR is devoted to the study of the mechanisms of chronic or persistent pain with specialized focus on 1) sex-related factors that influence pain, and 2) painful clinical conditions that demonstrate a high prevalence in women. The Center's research program is diverse, and ranges from molecular studies to systems physiology studies to clinical studies. Our working model is that research on pain has clearly shown that a person's sex is an important factor in determining their perception of, and response to, painful stimulation and pathological pain. Several physiological and psychological mechanisms have been proposed to account for these sex differences, yet many hypotheses remain to be adequately tested. This SCOR would direct its efforts to evaluating physiological models of sex-related pain differences, including the influence of gonadal hormones. Additionally, this Center would evaluate pathophysiological models of chronic pain conditions that are more prevalent in women, focusing on temporomandibular joint disorders (TMD) and the visceral pain associated with conditions such as irritable bowel syndrome (113S). This Center would facilitate the transfer of basic scientific knowledge to the study of persistent pain in humans, and ultimately to the development of new methods of diagnosing and treating these conditions in the general population. One clinical and two basic science projects constitute the scientific basis of the application. The two principal objectives of this SCOR are: 1) To elucidate the underlying mechanisms associated with sex differences in persistent pain of deep muscle and visceral origin. Human and animal studies will explore hypothesized physiological mechanisms of sex differences in pain, including opioid receptor expression, peripheral nociceptor sensitivity, CNS sensitization, and CNS ascending/descending modulation, as well as the influence of gonadal steroids on these mechanisms. All three projects address this objective. 2) To explore the neural basis of temporomandibular disorder (TMD) pain, with special emphasis upon sex-related hypotheses. TMD is the major persistent orofacial pain condition of deep tissue origin. It shows a large prevalence in women of childbearing age. The pathophysiology of TMD is poorly understood, but several hypotheses based on sex-related factors have been proposed. Two of the proposed projects (#1and #3) direct efforts explicitly to evaluate such hypotheses.

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Males and females differ in their sensitivity to pain. Females generally have more pain complaints and are more sensitive to pain than males. We do not fully understand why these sex differences in pain perception exist. If we would understand this better, more effective therapies for pain complaints could be developed in the future. The aim of the present study is to assess what role sex hormones, such as estrogen and progesterone, play in changing sensitivity to pain. In this study we will look at the activity in the brain that is related to the processing of the painful or nonpainful stimuli by using functional Magnetic Resonance Imaging (fMRI), which is a noninvasive measurement of brain function. Also, we will examine if these hormones influence brain activity during a difficult distracting task and, thus, may be responsible for sex-differences in analgesic responses. We will examine normally cycling healthy females during a pre-fMRI screening and training session and 4 times during their normal menstrual cycle. In the pre-fMRI screening and training session, participants will be screened and they will fill out several questionnaires and undergo a training session of all procedures. This first session will be performed in the mid-follicular phase in all women. To make sure that each participant is in her mid-follicular phase, blood will be drawn and levels of estradiol, progesterone, luteinizing hormone, follicle stimulating hormone, and testosterone will be determined. Two different stimuli will be used to cause painful stimulation: pressure and electrical current stimulation will be given to the left dorsal foot. Both pressure and electrical current stimulation are commonly used in clinical situations. For each participant, 2 stimulus levels will be selected: a non-painful stimulus and a painful stimulus corresponding to a pain intensity rating of moderate intensity. Participants will have to rate their pain intensity and pain unpleasantness on a visual analogue scale after each stimulus. These scales will have anchors for 'no pain'/ 'not at all unpleasant', and 'most intense pain imaginable'/ 'extremely unpleasant'. After this first session, the subjects will be asked to keep a daily diary of their body temperatures and the onset and duration of their menstruation and ovulation with an ovulation test kit for at least two whole menstrual cycles. Candidates for further study participation will be selected on the basis of this first screening session and the menstrual cycle diaries. Then pain-related brain activation will be assessed in 4 different phases of the menstrual cycle since hormone levels will be different across these phases: during their menstrual phase (2-4 days after menstruation onset), their mid-follicular phase (6-8 days after menstruation onset), around ovulation (about 14 days after menstruation onset), and during midluteal phase (around 20 days after menstruation onset). On all of these visits, questionnaires will be filled out and sensory testing will be performed. In addition, subjects will participate in a functional brain imaging session in which cortical activity following stimulation with nonpainful and painful stimuli will be examined, and following presentation of a difficult mental task. At each visit, a sample of urine will be collected to test for pregnancy since there is currently not enough information about the effects of MRI scanning on an unborn child. At each test day, some blood will be drawn to measure levels of estradiol, progesterone, luteinizing hormone, follicle stimulating hormone, and testosterone. Levels of cortisol will be determined in saliva (spit) samples. The objective of the study is that 16 participants complete the study successfully. Since some of the participants may drop out during the study, we expect to recruit up to 32 participants in this study.

DESCRIPTION (provided by applicant): According to the recent Institute of Medicine (IOM) report on Relieving Pain in America (2011), chronic pain is a public health epidemic affecting more than 116 million Americans and costing more than $600 billion per year in healthcare expenses and lost work productivity. More Americans suffer from pain than those afflicted with heart disease, diabetes and cancer combined. Despite recent advances in treatment, most people do not obtain adequate pain relief. An important focus has been on understanding the basic biology of chronic pain, so that new mechanistically based therapeutics can be developed. Unfortunately, standard research and development pipelines that start at the bench with several hundred known signaling pathways have not yielded many new targets in pain research. In a recent commentary, the NIH Director Francis Collins argued that these failures may be due to the feed-forward translational continuum from bench to beside that relies on biologically well-understood pathways. The result, in terms of drug development, is prolonged time to clinic, high failure rates and exorbitant cost. In this era of omics research, studies that incorporate geneti and genomic data may yield thousands of new, potentially druggable targets. The purpose of this Center for the Genomics of Pain is to combine rigorous phenotyping of pain and comorbid conditions with cutting edge genomics to more fully understand how individual differences can reduce or amplify pain. The Center's conceptual framework, adapted from Dr. William Maixner's model, incorporates comorbid pain conditions (intermediate risk factors), epigenetics, genomics, environment and gender to explain pain phenotypes. For the first time on the University of Maryland Baltimore Campus, geneticists, genomicists and pain researchers will combine their expertise to identify critical new therapeutic targets that can be exploited to reduce or eliminate chronic pain.

DESCRIPTION (provided by applicant): While virtually everyone experiences acute pain at some time, it is chronic pain that exacts a profound burden on the public health, reducing quality of life for tens of millions Americans, and incurring substantial health care costs. Yet little is known about mechanisms that cause a transition from acute to chronic pain; subsequently, event the best of treatments have limited efficacy. One likely clue regarding etiology is that patients who have one form of chronic pain often experience chronic pain elsewhere in the body. In this project, we hypothesize that the transition from acute to chronic pain and the development of multiple chronic pain conditions, are caused by specific constellations of genetic variants and phenotypic risk factors (ie. psychological distress, pain amplification and clinical pain characteristics). This hypothesis is based on our studies of temporomandibular disorder (TMD) in the multi-site OPPERA project (Orofacial Pain, Prospective Evaluation and Risk Assessment; NIH/NIDCR U01-DE017018). In 2006-08, we enrolled 3,263 healthy adults, 233 of whom developed acute TMD during the 3-year follow-up period. Risk factors for acute TMD differed conspicuously from genetic and phenotypic risk factors for chronic TMD. Furthermore, 86% of chronic TMD cases had one or more of four chronic, idiopathic pain conditions: headache (HA), low back pain (LBP), irritable bowel syndrome (IBS) or widespread bodily pain (WBP). In this competitive renewal application, we propose three new aims designed to reveal novel information regarding the etiology and pathophysiology of chronic pain. Aim 1: To identify phenotypes and genotypes that predict risk of transition from acute TMD to chronic TMD, we will enroll a new cohort of 1,000 adults who have acute TMD, following them for six months to identify an expected 400 who progress to chronic TMD. Aim 2 will identify risk factors for one or more of five: idiopathic pain conditions (IPCs): TMD, HA, LBP, IBS and/or WBP. Follow-up assessments will be conducted among people in the OPPERA-I prospective cohort study, identifying an expected 640 people who have ¿1 IPC. Existing phenotypes and genotypes measured at baseline will be used to predict risk of 1 IPC vs. ¿2 IPCs relative to controls. Aim 3 will identify genetic variants associated with chronic TMD. A discovery-phase genome wide association study (GWAS) will use existing DNA from 1,000 OPPERA-I chronic TMD cases and 1,000 OPPERA-I controls. Replication will use a new cohort of n=1,000 chronic TMD cases and n=1,000 controls. Those findings will be contrasted with GWAS analysis of the cohort for Aim 1 to identify genes that contribute differentially to acute and chronic TMD. Based on these findings and validated associations from other studies, twelve genes will be selected for exon sequencing of rare genetic variants. Knowledge generated from these proposed studies will have a significant impact on scientific understanding of risk factors for multiple, overlapping pai conditions. Moreover, the findings will be of direct benefit for clinicians and for their patients, elucidating mechanisms underlying chronic and idiopathic pain in people with TMD.

According to the recent Institute of Medicine (IOM) report on Relieving Pain in America (2011), chronic pain is a public health epidemic affecting more than 116 million Americans and costing more than $600 billion per year in healthcare expenses and lost work productivity. More Americans suffer from pain than those afflicted with heart disease, diabetes and cancer combined. Despite recent advances in treatment, most patients do not obtain adequate pain relief. Because we do not fully understand the mechanisms underlying chronic pain development and persistence, new approaches that take into account comorbid pain conditions and genomics are needed. The primary mission of our Center is to significantly advance the science underlying the genomic mechanisms of pain so that new drug targets can be elucidated and novel therapeutic interventions can be tested to eradicate pain. The conceptual basis for this core acknowledges that nociception (neural processing of noxious stimulation) and pain (unpleasant emotional experience) are multifactorial and that co-morbidities, for example depression, anxiety, stress, and fear, significantly influence these processes (Figure 1 (Maixner et al., 2011). This stance is further supported in a recent review in which Mogil (2009) argues that rodent models of pain should be tested not just for nocifensive behaviors, but also for pain-affected phenomena such as cognition, depression, fear and anxiety. The same argument holds true when examining clinical chronic pain phenotypes (Diatchenko et al., 2006). The overarching mission of the Translational Phenotyping Core (TPC) is to provide services and support for rodent or clinical behavioral phenotyping and sample collection and processing. To achieve this mission, we propose the following aims: Aim 1. Support the collection, analysis, interpretation and dissemination of behavioral data for the four pilot studies included in the Center proposal as well as new studies as they arise. The core service capacity includes rodent and clinical testing equipment that will provide a wide range of phenotyping assays, including pain/nocifensive testing and assessment of depression, anxiety, fear and other comorbid pain conditions. In addition, although not proposed for the current pilot studies, equipment and resources are available for new pilot studies that will require assessment of plasticity in the spinal cord dorsal horn via electrophysiological recording and evaluation of gait disturbances. Aim 2. Promote interdisciplinary collaborations between basic, translational and clinical scientists involved in pain research through increased access to comprehensive services. Initially, this Core will primarily serve the Center pilot PIs. We envision that as we publish and market our core phenotyping services, utilization by interdisciplinary colleagues will increase and new collaborations will be formed to further accelerate pain research on campus. Aim 3. Acquire, maintain, and upgrade equipment and resources that can be used to support existing and future studies of pain. With expanded use, particularly by colleagues from various disciplines, we anticipate that user requests will necessitate the purchase of new equipment that can be used to supply additional assays that more completely address the pain phenotype. The core directors will survey the campus community and core users annually to determine user needs and obtain needed equipment. In addition, the core directors will keep detailed logs of service and maintenance contracts on each piece of equipment and calibrate instruments as needed.