Donna L Hammond
University Of Iowa
Project start date: 1991-03-01
Project end date: 2013-12-31
Sponsored Links Excellgen http://Excellgen.com
Opioid Mechanisms Of Analgesia
Donna L Hammond, Professor And Chair
University Of Iowa Iowa City, Ia 52242
Grant 5R01DA006736-15 from National Institute On Drug Abuse IRG: SCS
Abstract: Work in the previous award period demonstrated that persistent inflammatory nociception has important functional consequences for the activity of pain modulatory pathways that originate in the rostral ventromedial medulla (RVM). Persistent inflammatory nociception induced by i.pl. injection of complete Freund s adjuvant (CFA)results in a progressive and time-dependent enhancement of the antihyperalgesic and antinociceptive effects of _ or 5 opioid receptor agonists microinjected in the RVM, in a compensatory activation of opioid-mediated pain inhibitory )athways, and the possible expression of opioid receptors with a novel pharmacology. The overall goals of the next award period are to further examine the neurochemical and cellular mechanisms responsible for the enhancement of opioid mediated actions in the RVM and to begin to determine which characteristics of inflammatory injury are critical to neuronal plasticity in the RVM. The first specific aim will determine whether an increase in opioid receptor affinity and number, or an increase in the potency and efficacy of opioids at their respective receptors in the RVM mediate the enhanced antinociceptive and antihyperalgesic effects of DAMGO and DELT. Opioid receptor autoradiography will be used in conjunction with GTPgammaS autoradiography and binding assays to examine these parameters in saline- and CFA-treated rats and to determine whether decreases in KD or ECs0 or increases in Bmax or Emaxare temporally concordant with the time-dependent enhancement of opioid effects in vivo. The second specific aim will determine whether the presynaptic and postsynaptic inhibitory effects of DAMGO and DELT are enhanced in the RVM of CFA-treated rats and to relate these changes to identified populations of RVM neurons. Whole-cell voltage or current clamp recordings will be made from immunohistochemically identified populations of spinally-projecting neurons in the RVM of saline- and CFA-treated rats to determine whether and in which population of neurons the presynaptic and postsynaptic effects of mu and delta opioid receptor agonists are enhanced as a consequence of inflammatory injury. These studies will also determine how inflammatory injury alters the sensitivity of RVM neurons to endogenous excitatory and inhibitory inputs by construction of input-output curves. The third specific aim will determine to what extent the plasticity of the RVM is dependent on the nociceptive nature and temporal relevance of the inflammatory injury. Local anesthetic blockade at various times before and during the inflammatory process will be used to determine whether an acute noxious stimulus is sufficient or necessary to invoke long-term plasticity of RVM neurons, as well as determine whether these changes require a sustained input from primary afferents. This series of complementary behavioral pharmacological, neurochemical and electrophysiological studies will provide important new information about the mechanisms by which persistent inflammatory nociception alters the pharmacology and physiology of brainstem neurons that comprise an critical efferent pathway for the modulation of nociception and the production of analgesia by opioids.
Keywords: analgesia, inhibitor /antagonist, neural plasticity, neuropharmacology, opioid receptor, pain, pons, stimulant /agonist, analgesic, hyperalgesia, membrane protein, narcotic antagonist, pain threshold, receptor sensitivity, behavior test, laboratory rat, microinjection, voltage /patch clamp
Project start date: 1991-03-01
Project end date: 2009-03-31
5R01DA006736-15 (2007): $314678
5R01DA006736-14 (2006): $288068
5R01DA006736-13 (2005): $295000
5R01DA006736-03 (1993): $176143
5R01DA006736-02 (1992): $164351
5R01DA006736-17 (2010): $334125
5R01DA006736-06 (1997): $213460
5R01DA006736-11 (2002): $295439
5R01DA006736-10 (2001): $286835
5R01DA006736-09 (2000): $281811
Sponsored Links Excellgen http://Excellgen.com
5R01DA006736-05 (1996): $205808
Grants awarded to Donna L Hammond
Opioid Mechanisms Of Analgesia
Donna L Hammond, Professor And Chair
University Of Iowa Iowa City, Ia 52242
Grant 2R01DA006736-12A1 from National Institute On Drug Abuse IRG: SCS
Abstract: Work in the previous award period demonstrated that persistent inflammatory nociception has important functional consequences for the activity of pain modulatory pathways that originate in the rostral ventromedial medulla (RVM). Persistent inflammatory nociception induced by i.pl. injection of complete Freund s adjuvant (CFA)results in a progressive and time-dependent enhancement of the antihyperalgesic and antinociceptive effects of _ or 5 opioid receptor agonists microinjected in the RVM, in a compensatory activation of opioid-mediated pain inhibitory )athways, and the possible expression of opioid receptors with a novel pharmacology. The overall goals of the next award period are to further examine the neurochemical and cellular mechanisms responsible for the enhancement of opioid mediated actions in the RVM and to begin to determine which characteristics of inflammatory injury are critical to neuronal plasticity in the RVM. The first specific aim will determine whether an increase in opioid receptor affinity and number, or an increase in the potency and efficacy of opioids at their respective receptors in the RVM mediate the enhanced antinociceptive and antihyperalgesic effects of DAMGO and DELT. Opioid receptor autoradiography will be used in conjunction with GTPgammaS autoradiography and binding assays to examine these parameters in saline- and CFA-treated rats and to determine whether decreases in KD or ECs0 or increases in Bmax or Emaxare temporally concordant with the time-dependent enhancement of opioid effects in vivo. The second specific aim will determine whether the presynaptic and postsynaptic inhibitory effects of DAMGO and DELT are enhanced in the RVM of CFA-treated rats and to relate these changes to identified populations of RVM neurons. Whole-cell voltage or current clamp recordings will be made from immunohistochemically identified populations of spinally-projecting neurons in the RVM of saline- and CFA-treated rats to determine whether and in which population of neurons the presynaptic and postsynaptic effects of mu and delta opioid receptor agonists are enhanced as a consequence of inflammatory injury. These studies will also determine how inflammatory injury alters the sensitivity of RVM neurons to endogenous excitatory and inhibitory inputs by construction of input-output curves. The third specific aim will determine to what extent the plasticity of the RVM is dependent on the nociceptive nature and temporal relevance of the inflammatory injury. Local anesthetic blockade at various times before and during the inflammatory process will be used to determine whether an acute noxious stimulus is sufficient or necessary to invoke long-term plasticity of RVM neurons, as well as determine whether these changes require a sustained input from primary afferents. This series of complementary behavioral pharmacological, neurochemical and electrophysiological studies will provide important new information about the mechanisms by which persistent inflammatory nociception alters the pharmacology and physiology of brainstem neurons that comprise an critical efferent pathway for the modulation of nociception and the production of analgesia by opioids.
Keywords: analgesia, inhibitor /antagonist, neural plasticity, neuropharmacology, opioid receptor, pain, pons, stimulant /agonist, analgesic, hyperalgesia, membrane protein, narcotic antagonist, pain threshold, receptor sensitivity, behavior test, laboratory rat, microinjection, voltage /patch clamp
Project start date: 1991-03-01
Project end date: 2008-03-31
2R01DA006736-12A1 (2004): $295000
Interdisciplinary Training Program In Pain Research
Donna L Hammond, Professor And Chair
Anesthesiauniversity Of Iowa
iowa City, Ia 52242
Grant 5T32NS045549-05 from National Institute Of Neurological Disorders And Stroke IRG: NST
Abstract: This new application proposes an interdisciplinary program of training in pain research to be offered by the University of Iowa Pain Research Program. The program will focus on the cellular, molecular, pharmacological, physiological and anatomical mechanisms that sub-serve acute and chronic pain after injury. All 13-program faculties are NIH-funded investigators with complementary expertise in the fields of molecular, cellular and systems neurobiology. The trainers comprise a balanced representation of basic and physician scientists, as well as bench and patient-based research. Each member has a strong record of training pre-doctoral and post-doctoral fellows. Support is requested for one pre-doctoral trainee and three post-doctoral trainees for this initial award period. In line with our ultimate goal to facilitate translational research, efforts will be made to recruit M.D. and M.D./Ph.D. trainees to the post-doctoral positions. These individuals will particularly benefit from a period of protected time to learn the elements of research and/or to restart their research programs in advance of a faculty level appointment. The proposed training program provides a highly structured and diverse program of didactic coursework, including monthly seminars, weekly journal clubs and biweekly work-in-progress meetings. This didactic work is coupled with a period of 2-3 years of research training in a highly collaborative and interactive environment. All courses, as well as mechanisms of interaction and trainee evaluation are established. The overall goal of the training program is to provide our trainees with 1) an individualized curriculum that provides a solid knowledge base appropriate to their career plans; 2) rigorous training in the elements of scientific investigation including the formulation of research hypotheses, experimental design and analysis; 3) mastery of two to three research techniques; 4) opportunities to develop their verbal communication skills; 5) experience in the construction of manuscripts and grant proposals; and 6) the ability to interact and collaborate with basic and physician scientists both within and outside the institution who are actively engaged in research. Trainees in this program will acquire the knowledge, experience, and skill sets necessary for successful transition to an independent research career in academia, industry or government
Project start date: 2004-07-01
Project end date: 2009-06-30
5T32NS045549-05 (2008): $2412
5T32NS045549-04 (2007): $156731
5T32NS045549-03 (2006): $80682
5T32NS045549-02 (2005): $211222
1T32NS045549-01A1 (2004): $211222
5T32NS045549-07 (2010): $192278
3T32NS045549-07S1 (2010): $27950
2T32NS045549-06 (2009): $214567
CONTROL OF NOCICEPTION BY GABA
Donna L Hammond, Professor And Chair
Anesthesiologyuniversity Of Chicago
5801 S Ellis Ave
chicago, Il 60637
Grant 3R01DE011423-09S1 from National Institute Of Dental & Craniofacial Research IRG: DABR
Abstract: Previous studies of the pharmacologic and physiologic mechanisms of antinociception have focused primarily on the involvement of opioid peptides and monoamines. Although several lines of evidence implicate GABA in the modulation of nociception, limitations in our understanding of the pharmacology of GABA receptors and a paucity of drugs with which to manipulate these receptors have severely hampered studies of the role of GABA to date. However, recent advances in the pharmacology of both GABAA and GABAB receptors now provide the tools with which to more thoroughly characterize the role of GABA in antinociception. This proposal will systematically characterize involvement of GABAA and GABAB receptors in the modulation of nociception by neurons in three regions of the CNS for which the pharmacologic and physiologic mechanisms of antinociception have been best characterized the spinal cord, n. raphe magnus and n. reticularis gigantocullaris pars alpha. These studies will first assess the effects of GABAA and GABAB agonists and antagonists on nociceptive sensitivity and motor function following intracerebral microinjection and intrathecal injection. The pharmacologic specificity of these effects will then be determined. With respect to the GABAA receptor, these studies will determine whether benzodiazepine agonists in a manner consonant with GABAA receptor pharmacology. Of particular interest will be the determination of (1) whether GABAA receptors involved in nociception are linked to a benzodiazepine modulatory site as it now appears that not all GABAA sites are linked to benzodiazepine sites and (2) whether a specific subtype of the GABAA receptor mediates antinociception. With respect to the GABAB receptor, these studies will determine, using the newly introduced GABAB antagonists, whether the antinociception produce by baclofen is truly mediated by a GABAB receptor or by a "baclofen" receptor. Finally, this proposal will also examine the pharmacology of the neuronal pathways that mediate the effects of GABAA and GABAB receptor agonists and antagonists on nociception. Using a multidisciplinary approach, these studies will determine whether GABAergic modulation of nociception is mediated by activation or inhibition of a bulbospinal serotonergic projection originating in the n. raphe magnus. The results of these studies will provide new insights into non-opioid mechanisms of antinociception
Keywords: GABA receptor, analgesic, gamma aminobutyrate, neurotransmitter, opioid, pain threshold anesthetic, barbiturate, benzodiazepine, brain /spinal pathway /tract, dorsal raphe nucleus, inhibitor /antagonist, serotonin, serotonin inhibitor, spinal cord, stimulant /agonist drug administration route, laboratory rat, microinjection
Project start date: 1990-06-01
Project end date: 2000-07-31
3R01DE011423-09S1 (1998): $30441
Sponsored Links Excellgen http://Excellgen.com
5R01DE011423-09 (1998): $225353
5R01DE011423-08 (1997): $216686
5R01DE011423-06 (1995): $202333
9R01DE011423-05 (1994): $194737
ROLE OF MEDULLARY SUBSTANCE P IN ACUTE AND PERSISTENT NOCICEPTION
Donna L Hammond, Professor
University Of Iowa, Iowa City, Ia 52242
Grant 5R01DA023576-03 from National Institute On Drug Abuse
Abstract: Our understanding of the mechanisms by which inflammatory injury leads to sustained changes in the function and properties of pain modulatory neurons in the rostral ventromedial medulla (RVM) remains rudimentary. Substance P (SubP) contributes to central sensitization after injury, yet surprisingly little is known about its role in the modulation of nociception by the RVM, where it also exists in high concentrations. Pilot data indicate that SubP has both antinociceptive and pronociceptive actions in the RVM in the uninjured state, but acts to mediate and sustain hyperalgesia after inflammatory injury. These data support four related hypotheses. 1) SubP exerts both pronociceptive and antinociceptive effects in the uninjured state by time-dependent activation of pain inhibitory and pain facilitatory bulbospinal pathways. Behavioral pharmacological studies will establish the dose-dependence and duration of SubP effects in the RVM of rats in the uninjured state, and confirm the role of neurokinin-1 (NK1) receptors. The bulbospinal pathways that mediate the effects of SubP will be determined by challenge with spinally-administered receptor antagonists before and at various times after SubP injection. 2) SubP is released in the RVM in response to inflammatory injury, where it plays a pronociceptive role in the development of hyperalgesia. The role of endogenous SubP released in the RVM after injury will be assessed by NK1 receptor internalization and by microinjection of NK receptor antagonists in the RVM of rats with acute and persistent hyperalgesia induced by complete Freund´s adjuvant (CFA). 3) SubP effects reflect the expression of the NK1 receptor by specific types of RVM neurons, a pattern that may change after injury. Tract tracing and immunohistochemistry will identify RVM neurons that express NK1 receptors by their neurotransmitter content and projections to the spinal cord and DLPT. Subsequent studies will determine whether this expression changes after CFA, and will identify the types of RVM neurons in which NK1 receptor internalization (indicative of SubP release) occurs after injury. 4) SubP acts at specific populations of spinally-projecting RVM neurons and, in CFA-treated rats, enhances excitatory inputs to specific types of RVM neurons to mediate hyperalgesia. Whole-cell patch clamp recording from RVM neurons, coupled with retrograde labeling and immunohistochemical staining, will identify which types of RVM neurons express functional NK1 receptors and determine how the actions of SubP change after CFA. Extracellular recordings will determine the effect of SubP on ON, OFF and NEUTRAL cells and its role in the sensitization of these neurons after CFA. These studies will provide a mechanistic framework in which the antinociceptive and pronociceptive effects of SubP are related to specific populations of RVM neurons. These data in turn may enable us to identify their function (pro- vs antinociceptive). Collectively, these results will advance our understanding of the means and mechanisms by which peripheral inflammatory injury alters the responses and function of critical brainstem pain modulatory systems, and inform a more rationale development of centrally-acting analgesics for the relief of persistent pain. PUBLIC HEALTH RELEVANCE Persistent pain of an inflammatory nature, such as that associated with arthritis or soft tissue injury, exacts a significant financial, emotional and physical toll on its sufferers. The results of these studies will identify how persistent pain changes the function of brainstem pathways that are critically involved in the regulation of nociception and the production of analgesia. Insights gain from this work will guide the development of new, more effective pharmacotherapies or cognitive approaches for the relief of persistent pain
Keywords: 1, 2-Benzenediol, 4-(2-amino-1-hydroxyethyl)-, (R)-; 3-(2-Aminoethyl)-1H-indol-5-ol; 4-Aminobutanoic Acid; 4-Aminobutyric Acid; 5-HT; 5-Hydroxytryptamine; 5HT; 6-namide, N-((4-hydroxy-3-methoxyphenyl)methyl)-8-methyl-, (E)-; 8-Methyl-N-Vanillyl-6-namide; Absence of pain sensation; Absence of sensibility to pain; Acute; Adrenergic Receptor; Adrenoceptors; Afferent Neurons; Aminalon; Aminalone; Aminobutyric Acids; Analgesic Agents; Analgesic Drugs; Analgesic Preparation; Analgesics; Anodynes; Antinociceptive Agents; Antinociceptive Drugs; Arthritis; Behavioral; Brain; Brain Stem; Brainstem; Butanoic acid, 4-amino-; Capsaicin; Cell Nucleus; Cell/Tissue, Immunohistochemistry; Cells; Central gray substance of midbrain; Cerebrospinal Fluid; Chronic inflammatory pain; Cognitive; Common Rat Strains; Coupled; Data; Dependence; Development; Dorsal Horn of the Spinal Cord; Dose; Drug Therapy; Emotional; Encephalon; Encephalons; Enteramine; Euler-Gaddum Substance P; Feels no pain; Freund`s Adjuvant; Freund`s Complete Adjuvant; Fugu Toxin; Future; GABA; Glutamate Carboxy-Lyase; Glutamate Decarboxylase; Glutamic Acid Decarboxylase; Goals; Heating; Hippophaine; Hyperalgesia; Hyperalgesic Sensations; IHC; Immunohistochemistry; Immunohistochemistry Staining Method; Immunostimulants, adjuvants, Freund`s; Inflammatory; Injection of therapeutic agent; Injections; Injury; Investigators; Knowledge; L-Glutamate-1-carboxy-lyase; L-tryptophan, tetrahydropteridine[{..}]oxygen oxidoreductase (5-hydroxylating); Label; Levarterenol; Levonorepinephrine; Locus Coeruleus; Maintenance; Maintenances; Mammals, Rats; Mechanics; Mediating; Medulla Spinalis; Mesencephalic Central Gray; Microinjections; Midbrain Central Gray; Molecular; NK-1 Receptors; NK1R; NKIR; Nature; Nerve Cells; Nerve Transmitter Substances; Nerve Unit; Nervous System, Brain; Neural Cell; Neurocyte; Neurons; Neurons, Afferent; Neurons, Sensory; Neurotransmitters; No sensitivity to pain; Nociception; Noradrenaline; Norepinephrine; Nucleus; Nucleus Pigmentosus Pontis; Outcome; Pain; Painful; Pathway interactions; Pattern; Periaqueductal Gray; Peripheral; Persistent pain; Pharmacology; Pharmacotherapy; Physicians; Physiology; Play; Pons; Pons Cerebelli; Pons Varolii; Pontine; Pontine structure; Population; Production; Property; Property, LOINC Axis 2; Rat; Rattus; Receptor Protein; Receptors, Epinephrine; Receptors, Neurokinin-1; Regulation; Research; Research Personnel; Researchers; Role; SP(1-11); SP-P Receptors; Sensory Cell Afferent Neuron; Series; Serotonin; Site; Slice; Soft Tissue Injuries; Spinal Cord; Spinal cord posterior horn; Staining method; Stainings; Stains; Stiefel Brand of Capsaicin; Structure of locus ceruleus; Substance P; Substance P Receptor; Synapses; Synaptic; System; System, LOINC Axis 4; TAC1R; TACR1; TTX; Tachykinin Receptor 1; Tag; Tail; Tarichatoxin; Tegmentum Mesencephali; Testing; Tetradotoxin; Tetrodotoxin; Thermal Hyperalgesias; Time; Tracer; Tryptophan 5-monooxygenase; Tryptophan Hydroxylase; Tryptophan Monooxygenase; Withdrawal; Work; adenoreceptor; allodynia; analgesia; annulus of the aqueduct; arthritic; blue nucleus; central sensitization; chronic pain; chronic painful condition; experiment; experimental research; experimental study; extracellular; gamma-Aminobutyric Acid; hyperalgia; innovate; innovation; innovative; insight; locus ceruleus structure; midbrain central gray substance; neurokinin 1; neuronal; nociceptive; noradrenergic; patch clamp; pathway; periaqueductal gray matter; postsynaptic; public health relevance; puffer fish toxin; receptor; receptor internalization; research study; response; social role; spinal fluid; tegmentum; tryptophan 5 hydroxylase
Relevance: Persistent pain of an inflammatory nature, such as that associated with arthritis or soft tissue injury, exacts a significant financial, emotional and physical toll on its sufferers. The results of these studies will identify how persistent pain changes the function of brainstem pathways that are critically involved in the regulation of nociception and the production of analgesia. Insights gain from this work will guide the development of new, more effective pharmacotherapies or cognitive approaches for the relief of persistent pain
Project start date: 2008-09-30
Project end date: 2013-05-31
Budget start date: 1-JUN-2010
Budget end date: 31-MAY-2011
PFA/PA: PA-07-282
5R01DA023576-03 (2010): $578128
5R01DA023576-02 (2009): $566960
Role Of Spinal GABA Receptors In Neuropathic Pain
Donna L Hammond, Professor And Chair
University Of Iowa Iowa City, Ia 52242
Grant 5R01DA016430-03 from National Institute On Drug Abuse IRG: SCS
Abstract: Loss of GABA-mediated inhibition in the spinal cord is proposed to contribute to the development and maintenance of neuropathic pain. However, the supporting data are surprisingly weak. Further, these studies have not considered the complex molecular biology of GABA receptors, and how subunit composition and pharmacology change in disease states and under conditions of repetitive activity as occurs after nerve injury. We hypothesize that nerve injury causes immediate, as well as long-term changes in the expression, distribution and subunit composition of GABAA or GABAB receptors in the spinal cord. We propose to characterize these changes in the context of defined presynaptic and postsynaptic elements of the afferent pain pathways and a well-characterized model of spinal nerve ligation that exhibits time-dependent changes in neuropathic pain behaviors. Of particular importance are the changes induced in the expression and molecular composition of these receptors on uninjured, and on injured primary afferent neurons and on dorsal horn neurons as a function of time after nerve injury. Changes in the expression and subunit composition of GABAA and GABAB receptor subunits in the spinal cord dorsal horn, and in ipsilateral and contralateral L4 and L5 DRG of ligated and sham rats will be determined by Western blot. Two-color indirect immunofluorescence methods will be used with stereological measurements to examine the distribution of GABAA and GABAB receptor subunits on different populations of immunohistochemically-identified primary afferent neurons in the L4 and L5 DRG of ligated and sham-operated rats. Immunohistochemical methods will also be used in conjunction with retrograde labeling of spinothalamic and spinoparabrachial neurons in ligated and sham rats to determine whether the distribution and composition of postsynaptic GABAA and GABAB receptors in the spinal cord dorsal horn is also altered after nerve injury. Time points for analysis will range 7 to 140 days after injury. These studies will provide new information about the distribution of GABAA and GABAB receptors on identified populations of primary afferent neurons and dorsal horn neurons in the naive animal. They will describe how the distribution and molecular composition of these receptors changes as a function of time after nerve injury and provide new insights into the molecular and neuroanatomical bases of inhibitorv svnaptic transmission in the spinal cord.
Keywords: GABA receptor, molecular biology, nerve injury, neuropathology, pain, protein localization, receptor expression, spinal nerve, afferent nerve, dorsal horn, neurosurgery, spinal ganglion, behavior test, immunofluorescence technique, laboratory rat, protein quantitation /detection, western blotting
Project start date: 2004-07-05
Project end date: 2008-04-30
5R01DA016430-03 (2006): $288068
5R01DA016430-02 (2005): $295000
Spinal GABA Receptors In Neuropathic Pain
Donna L Hammond, Professor And Chair
University Of Iowa Iowa City, Ia 52242
Grant 1R01DA016430-01A2 from National Institute On Drug Abuse IRG: SCS
Abstract: Loss of GABA-mediated inhibition in the spinal cord is proposed to contribute to the development and maintenance of neuropathic pain. However, the supporting data are surprisingly weak. Further, these studies have not considered the complex molecular biology of GABA receptors, and how subunit composition and pharmacology change in disease states and under conditions of repetitive activity as occurs after nerve injury. We hypothesize that nerve injury causes immediate, as well as long-term changes in the expression, distribution and subunit composition of GABAA or GABAB receptors in the spinal cord. We propose to characterize these changes in the context of defined presynaptic and postsynaptic elements of the afferent pain pathways and a well-characterized model of spinal nerve ligation that exhibits time-dependent changes in neuropathic pain behaviors. Of particular importance are the changes induced in the expression and molecular composition of these receptors on uninjured, and on injured primary afferent neurons and on dorsal horn neurons as a function of time after nerve injury. Changes in the expression and subunit composition of GABAA and GABAB receptor subunits in the spinal cord dorsal horn, and in ipsilateral and contralateral L4 and L5 DRG of ligated and sham rats will be determined by Western blot. Two-color indirect immunofluorescence methods will be used with stereological measurements to examine the distribution of GABAA and GABAB receptor subunits on different populations of immunohistochemically-identified primary afferent neurons in the L4 and L5 DRG of ligated and sham-operated rats. Immunohistochemical methods will also be used in conjunction with retrograde labeling of spinothalamic and spinoparabrachial neurons in ligated and sham rats to determine whether the distribution and composition of postsynaptic GABAA and GABAB receptors in the spinal cord dorsal horn is also altered after nerve injury. Time points for analysis will range 7 to 140 days after injury. These studies will provide new information about the distribution of GABAA and GABAB receptors on identified populations of primary afferent neurons and dorsal horn neurons in the naive animal. They will describe how the distribution and molecular composition of these receptors changes as a function of time after nerve injury and provide new insights into the molecular and neuroanatomical bases of inhibitorv svnaptic transmission in the spinal cord.
Keywords: GABA receptor, molecular biology, nerve injury, neuropathology, pain, protein localization, receptor expression, spinal nerve, afferent nerve, dorsal horn, neurosurgery, spinal ganglion, behavior test, immunofluorescence technique, laboratory rat, protein quantitation /detection, western blotting
Project start date: 2004-07-05
Project end date: 2007-04-30
1R01DA016430-01A2 (2004): $292255
Opioid Mechanisms Of Analgesia
Donna L Hammond, Professor And Chair
Anesthesiauniversity Of Iowa
Grant 2R01DA006736-16 from National Institute On Drug Abuse IRG: SCS
Abstract: By comparison to the primary afferent and dorsal horn neurons, our understanding of the mechanisms by which peripheral inflammatory injury leads to sustained changes in the function and properties of brainstem neurons that modulate nociception remains rudimentary. This laboratory was the first to identify that persistent inflammatory nociception enhances the antinociceptive and anti-hyperalgesic effects of MOR and DOR agon- ists in the brainstem, providing early direct evidence that persistent inflammatory nociception alters the phar- macology and physiology of bulbospinal pain modulatory neurons. Whole-cell patch-clamp recordings from RVM neurons have now identified two populations of spinally-projecting RVM neurons, one serotonergic and the other non-serotonergic, in which the postsynaptic inhibitory effect of a MOR agonist is enhanced in CFA- treated rats. These neurons also exhibit alterations in their passive membrane properties or spontaneous ac- tivity, and the strength of glutamatergic inputs to the non-serotonergic neurons is greatly increased in CFA- treated rats. We hypothesize that these neurons correspond to two populations of pain facilitatory neurons. We now propose to investigate the presynaptic mechanisms by which MOR and DOR agonists act in the RVM to produce anti-hyperalgesia. The first specific aim will use whole-cell patch clamp recording from retrogradely labeled, immunohistochemically identified RVM neurons to test three hypotheses 1) that persistent inflamma- tory nociception increases excitatory drive to specific populations of spinally-projecting RVM neurons; 2) that it enhances the ability of MOR, and possibly DOR, agonists to inhibit excitatory drive to these neurons; and 3) that the mechanism of opioid enhancement entails an upregulation of MOR, but not DOR, on glutamatergic afferents to these neurons. The second specific aim will also use whole-cell patch clamp recording to test three complementary hypotheses 1) that persistent inflammatory nociception differentially alters inhibitory drive to specific populations of spinally-projecting RVM neurons, 2) that it increases the ability of MOR and DOR agon- ists to inhibit inhibitory drive to these same neurons; and 3) that the mechanism of enhancement entails a dif- ferential upregulation of MOR and DOR on GABAergic terminals to these neurons. Immunohistochemistry will be used to quantitate colocalization of MOR or DOR immunoreactivity with vGLUT, a marker of glutamatergic terminals, or with vGAT, a marker of GABAergic terminals, in the RVM of saline- and CFA-treated rats to ob- tain complementary anatomical data to support or refute these hypotheses. The outcome of these experiments will be a mechanistic framework for the antinociceptive and anti-hyperalgesic effects of opioids in the RVM. In turn, through studies of this class of analgesic we will be better able to identify the function of the different types of RVM neurons that are critically involved in the nociception. These data will advance our understanding of how peripheral inflammatory injury alters the responses and function of critical brainstem pain modulatory systems and inform a more rationale development of centrally-acting analgesics for the relief of persistent pain. PUBLIC HEALTH RELEVANCE Persistent pain of an inflammatory nature, such as that associated with arthritis or soft tissue injury, exacts a significant financial, emotional and physical toll on its sufferers. The results of these studies will identify how persistent pain changes the function of brainstem pathways that are critically involved in the regulation of nociception and the production of analgesia. Insights gain from this work will guide the development of new, more effective pharmacotherapies or cognitive approaches for the relief of persistent pain
Project start date: 1991-03-01
Project end date: 2014-12-31
Sponsored Links Excellgen http://Excellgen.com
INFLAMMATORY NOCICEPTION EFFECT ON MEDULLARY NEURONS
Donna L Hammond, Professor And Chair
Anesthesiauniversity Of Iowa
iowa City, Ia 52242
Grant 7R03DA012491-02 from National Institute On Drug Abuse IRG: ZRG1
Abstract: Adapted From ´s ) Recent studies have revealed an unexpected plasticity of afferent pain pathways following neuropathic or inflammatory injury, and concomitant changes in the efficacy of opioid analgesics. Previous investigations of the effects of injury limited their examination to neurons in the periphery and the spinal cord. Consequently, very little is known about the effects of injury at the supraspinal level and, in particular, about the effects of inflammatory nociception on the pain modulatory pathways that originate in the pons or medulla. Neurons in NRM and NGCp alpha of the ventromedial medulla that project to the spinal cord comprise one of the important, common efferent pathways for the modulation of nociception, and are also implicated in the production of antinociception by opioid receptor agonists. Recent studies in this laboratory indicate that the antinociceptive effects of DAMGO, a mu opioid receptor agonist, are enhanced after microinjection in the NRM or NGCp alpha of rats with monoarthritis induced by intraplantar injection of CFA. However, the mechanism for this enhancement is unknown. This application proposes to use neuroanatomical and molecular neuroanatomical techniques to identify the mechanisms responsible for this enhancement. Its specific aims are to Use in situ hybridization histochemistry to identify alterations in the expression of mRNA for the endogenous opioid peptides and their receptors as a function of time after injury. Use immunocytochemistry to identify corresponding alterations in the number and distribution of neurons immunoreactive for these peptides and their receptors. These experiments will provide new insights into the effects of inflammatory nociception on brainstem neurons that comprise an important efferent pathway for the modulation of nociception and a key site of action for opioid analgesics. Moreover, the findings of these experiments will be strengthened by our ability to relate these alterations to the results of ongoing pharmacological investigations of the effects of opioid receptor agonists and antagonists in the ventromedial medulla after inflammatory injury
Keywords: brain stem, inflammation, neuropeptide receptor, opioid receptor, pain brain /spinal pathway /tract, messenger RNA, nerve injury, neural plasticity, neuroanatomy, receptor expression immunocytochemistry, in situ hybridization, laboratory rat, microinjection
Project start date: 1999-04-01
Project end date: 2003-03-31
7R03DA012491-02 (2000): $72677
CONTROL OF NOCICEPTION BY GABA
Donna L Hammond, Professor And Chair
Anesthesia And Critical Careuniversity Of Chicago
5801 S Ellis Ave
chicago, Il 60637
Grant 3R01DE011423-08S1 from National Institute Of Dental & Craniofacial Research IRG: DABR
Project start date: 1990-06-01
Project end date: 1999-07-31
3R01DE011423-08S1 (1998): $2537
5R01DE011423-07 (1996): $208352