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Dhar D, Poree LR, Yaksh TL. Evolution of the Spinal Delivery of Opiate Analgesics. Neuromodulation 2018. [DOI: 10.1016/b978-0-12-805353-9.00065-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Salas R, Ramirez K, Vanegas H, Vazquez E. Activity correlations between on-like and off-like cells of the rostral ventromedial medulla and simultaneously recorded wide-dynamic-range neurons of the spinal dorsal horn in rats. Brain Res 2016; 1652:103-110. [PMID: 27720764 DOI: 10.1016/j.brainres.2016.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 09/27/2016] [Accepted: 10/01/2016] [Indexed: 12/27/2022]
Abstract
Considerable evidence supports the notion that on- and off-cells of the rostral ventromedial medulla (RVM) facilitate and depress, respectively, spinal nociceptive transmission. This notion stems from a covariation of on- or off-cell activities and spinal nocifensive reflexes. Such covariation could theoretically be due to their independently responding to a common source, or to an RVM-derived modulation of ventral horn neurons. Here, we tested whether on- and off-cells indeed modulate spinal nociceptive neurons. In deeply anesthetized rats, unitary recordings were simultaneously made from an RVM on-like or off-like cell and a spinal nociceptive neuron that shared a receptive field (RF) at a hind paw. Action potential firing in RVM/spinal neuron pairs was highly correlated, positively for on-like cells and negatively for off-like cells, both during ongoing activity and during application of calibrated noxious pressure to the RF. Microinjection of morphine into RVM induced a correlated decrease in on-like cell/spinal neuron ongoing activity and response to noxious stimulation. RVM morphine induced changes in off-like cell activity that were not correlated with spinal neuronal activity. These results suggest that on-cells exert a positive modulation upon spinal nociceptive neurons, upstream to ventral horn circuits and plausibly at the origin of nociceptive information that eventually reaches the cerebral cortex. On-cells may in this manner contribute to inflammation- and neuropathy-induced increases in withdrawal reflexes. Most significantly, on-cell modulation of nociceptive neurons may be a key factor in clinical pain conditions such as hyperalgesia and allodynia.
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Affiliation(s)
- Rafael Salas
- Catedra de Fisiologia, Escuela de Bioanalisis, Facultad de Medicina, Universidad Central de Venezuela, Apartado 9995, Caracas 1050, Venezuela.
| | - Karla Ramirez
- Laboratorio de Neurofisiologia, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.
| | - Horacio Vanegas
- Laboratorio de Neurofisiologia, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.
| | - Enrique Vazquez
- Laboratorio de Neurofisiologia, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.
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Abstract
UNLABELLED Treating pain is one of the most difficult challenges in medicine and a key facet of disease management. The isolation of morphine by Friedrich Sertürner in 1804 added an essential pharmacological tool in the treatment of pain and spawned the discovery of a new class of drugs known collectively as opioid analgesics. Revered for their potent pain-relieving effects, even Morpheus the god of dreams could not have dreamt that his opium tincture would be both a gift and a burden to humankind. To date, morphine and other opioids remain essential analgesics for alleviating pain. However, their use is plagued by major side effects, such as analgesic tolerance (diminished pain-relieving effects), hyperalgesia (increased pain sensitivity), and drug dependence. This review highlights recent advances in understanding the key causes of these adverse effects and explores the effect of chronic pain on opioid reward. SIGNIFICANCE STATEMENT Chronic pain is pervasive and afflicts >100 million Americans. Treating pain in these individuals is notoriously difficult and often requires opioids, one of the most powerful and effective classes of drugs used for controlling pain. However, their use is plagued by major side effects, such as a loss of pain-relieving effects (analgesic tolerance), paradoxical pain (hyperalgesia), and addiction. Despite the potential side effects, opioids remain the pharmacological cornerstone of modern pain therapy. This review highlights recent breakthroughs in understanding the key causes of these adverse effects and explores the cellular control of opioid systems in reward and aversion. The findings will challenge traditional views of the good, the bad, and the ugly of opioids.
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Somers DL, Clemente RF. The neurophysiological basis of peripheral electrical nerve stimulation for the treatment of causalgia. PHYSICAL THERAPY REVIEWS 2013. [DOI: 10.1179/ptr.1996.1.1.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Mejia-Gervacio S. Muscarinic control of AMPA receptor responsiveness in mouse spinal cord motoneurons. J Physiol 2012; 590:4663-71. [PMID: 22890702 DOI: 10.1113/jphysiol.2012.238444] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A cholinergic synaptic input has been highlighted in recent years as an important modulator of motoneuron excitability. In the present study, it was examined whether, as in other regions, the cholinergic inputs on spinal motoneurons modulate the glutamatergic synaptic activity, evoked by electrical stimulation at the dorsolateral funiculus. The present results show that the pharmacological stimulation of muscarinic receptors produces a selective depression of AMPA-mediated glutamatergic activity in thoracic and lumbar spinal motoneurons. This effect does not involve a change in transmitter release and occurs both on synaptic currents and on AMPA responses evoked by photolysis of MNI-glutamate. Thus, it is concluded that muscarinic modulation occurs at the postsynaptic level. The results suggest that cholinergic inputs contacting motoneurons, which are known to increase motoneuron excitability, also directly interfere within coming synaptic inputs by changing their amplitudes.
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Affiliation(s)
- Sheyla Mejia-Gervacio
- Laboratoire de Physiologie Cérébrale, CNRS UMR 8118, 45 rue des Saints Pères, 75006 Paris, France.
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DUGGAN A, HALL J, HEADLEY P. SUPPRESSION OF TRANSMISSION OF NOCICEPTIVE IMPULSES BY MORPHINE: SELECTIVE EFFECTS OF MORPHINE ADMINISTERED IN THE REGION OF THE SUBSTANTIA GELATINOSA. Br J Pharmacol 2012. [DOI: 10.1111/j.1476-5381.1977.tb09740.x] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Communication among neurons includes new permutations of molecular, electrical, and mechanical factors. Behav Brain Sci 2011. [DOI: 10.1017/s0140525x0006338x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Neuronal communication and synaptic modulation: experimental evidence vs. conceptual categories. Behav Brain Sci 2011. [DOI: 10.1017/s0140525x00063548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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The trace amines: neurohumors (cytosolic, pre- and/or post-synaptic, secondary, indirect)? Behav Brain Sci 2011. [DOI: 10.1017/s0140525x00063354] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
AbstractRecently a number of complex electrophysiological responses to neurotransmitters have been observed that cannot be described as simple excitation or inhibition. These responses are often characterized as modulatory, although there is no consensus on what defines modulation. Morphological studies reveal certain neurotransmitters stored in what might be release sites without synaptic contact. There is no direct evidence for nonsynaptic release from CNS sites, although such release does occur in the periphery and in invertebrates. Nonsynaptic release might provide a basis for diffuse one-cell-to-many communication, but it might also simply be a means of sending the transmitter to a broader area of a single neuron than occurs in typical synapses. Several kinds of macromolecules have been found to be transported in a retrograde direction – and in some cases transsynaptically. There have been suggestions that some neurons may release more than one type of transmitter. Particularly intriguing is the possibility of release of substances that modulate actions of a primary transmitter. Taken together this range of evidence suggests that neurons may use a variety of forms of molecular communication in addition to traditionally described synaptic transmission.Several authors have suggested modes of communication distinct from classical synaptic transmission and have classified released substances using terms such as neurohumor, neurohormone, neuroregulator, and modulator. These suggestions have the heuristic value of drawing together diverse kinds of data, but it remains to be established that the pieces fit together in that fashion – for example, that complex electrophysiological effects are associated with substances released nonsynaptically. In order to reduce confusion, a flexible, generic approach to nomenclature for substances released from neurons and for hypothetical modes of communication is recommended. Some behavioral implications of nonconventional transmission are considered.
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Abstract
The techniques of manual medicine provide the basis for the palpatory recognition of dysfunction, primarily in the musculoskeletal system. The essential criterion of manual medicine is inclusion of the segmental level of function. One criterion of evaluation is, most notably, segmental hypomobility. The purpose of manual diagnostics is to determine segmental blockage. Manual therapy techniques lead first to improved function of the segment and, consequently, to improved function of the whole organism. Manual medicine focuses on the (peri)articular and myofascial levels as well as on the nervous control level of the motion segment and may interact with therapeutic methods. For therapeutic purposes, the joint may be manipulated with impulse as well as without therapeutic impulse for soft techniques. Different muscle relaxation techniques are used on the myofascial system to achieve improved function of reflectory or structurally altered musculature and of the myofascial system.
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Affiliation(s)
- R Kayser
- Klinik und Poliklinik für Orthopädie und Orthopädische Chirurgie, Universitätsklinikum Greifswald, Ferdinand-Sauerbruch-Strasse, 17475 Greifswald.
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Tongjaroenbuangam W, Jongkamonwiwat N, Phansuwan-Pujito P, Casalotti SO, Forge A, Dodson H, Govitrapong P. Relationship of opioid receptors with GABAergic neurons in the rat inferior colliculus. Eur J Neurosci 2006; 24:1987-94. [PMID: 17040471 DOI: 10.1111/j.1460-9568.2006.05098.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The inferior colliculus is a critical structure for processing auditory information and receives ascending and descending synaptic auditory projections. In addition to GABAergic and glutamatergic innervations, other neurotransmitter systems are also reported in the inferior colliculus, including opioid peptides. In the present study, the relative distribution of each type of opioid receptor, mu (MOR), delta (DOR) and kappa (KOR) within GABAergic neurons in the inferior colliculus was examined. GABA immunoreactivity was expressed by small, medium and large neurons and distributed in the central nucleus and the pericentral nucleus of the inferior colliculus. Immunostaining for MOR, DOR and KOR receptors was found in both disc-shaped cells and stellate cells. Punctiform beta-endorphin immunolabelling was observed in the proximity of GABA-positive neurons. Co-localization of GABA and MOR receptors was observed in neurons and nerve terminals in the central nucleus, dorsal cortex and external cortex of the inferior colliculus. Quantification of the co-localization patterns determined that a higher proportion of GABA neurons was associated with MOR receptors compared with KOR or DOR receptors.
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Affiliation(s)
- W Tongjaroenbuangam
- Neuro-Behavioral Biology Center, Institute of Science and Technology for Research and Development, Mahidol University, Salaya Campus, Nakornpathom 73170, Thailand
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Abstract
The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to clone a cDNA fragment of a putative G-protein-coupled receptor from rat brain total RNA. Nucleotide sequencing of this cDNA fragment showed it to be homologous to that of the mu-opioid receptor splice variant MOR(1C) from mice. We used the cDNA to make an RNA probe for a ribonuclease protection assay (RPA). The results from the RPA showed a protected fragment of the size expected for MOR(1C) mRNA, as well as other RNase-protected fragments that may indicate the existence of other MOR1 transcripts. We then used the RNA probe for in situ hybridization (ISH) experiments. We detected strong autoradiographic labeling over much of the rat telencephalon, diencephalon, mesencephalon, cerebellum, spinal cord, and dorsal root ganglia. These findings suggest that MOR(1C), and possibly other MOR1 splice variants, are important components of the system by which the actions of opioids are transduced.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Brain/metabolism
- Cloning, Molecular/methods
- DNA, Complementary/biosynthesis
- DNA, Complementary/genetics
- Male
- Molecular Sequence Data
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/isolation & purification
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, mu/biosynthesis
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/isolation & purification
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Affiliation(s)
- Stephen A Schnell
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55405, USA.
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Hoffmann VLH, Vermeyen KM, Adriaensen HF, Meert TF. Effects of NMDA receptor antagonists on opioid-induced respiratory depression and acute antinociception in rats. Pharmacol Biochem Behav 2003; 74:933-41. [PMID: 12667908 DOI: 10.1016/s0091-3057(03)00020-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Although exogenous opioids alter the responses of animals to tissue-damaging stimuli and therefore are the cornerstone in the treatment of acute antinociception, they have profound side effects on ventilation. To diminish ventilatory effects, combination therapies have been advocated. Recent studies reported the effectiveness of the addition of N-methyl-D-aspartate (NMDA) receptor antagonists such as ketamine to morphine in the treatment of acute pain. However, NMDA receptors, together with non-NMDA receptors are known to be involved in the neurotransmission of inspiratory drive to phrenic motoneurons. Co-administration of NMDA and non-NMDA receptor antagonists has been shown to be deleterious to respiratory function. The present study investigated the hypothesis that the association of opioids and NMDA receptor antagonists may add to the impairment of respiratory parameters. In male Wistar rats, combinations of opioids (fentanyl or morphine) at antinociceptive doses and NMDA receptor antagonists (ketamine, 40 mg/kg, or dextromethorphan, 10 mg/kg) at subanesthetic doses were administered intraperitoneally. Antinociception was tested with the tail-withdrawal reaction (TWR) test, while the effect on respiratory parameters was investigated with blood-gas analysis. We found that, in rats, co-administration of NMDA receptor antagonists and opioids may result in an increased respiratory depression as compared to the opioids alone. The effect of the NMDA receptor antagonists on opioid-induced antinociception was limited.
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Degtyarenko AM, Kaufman MP. Bicuculline attenuates the MLR-induced suppression of dorsal horn neurons receiving group III afferent input. Brain Res 2002; 935:109-13. [PMID: 12062479 DOI: 10.1016/s0006-8993(02)02418-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In decerebrate cats, we found that iontophoretic application of bicuculline, a GABA(A) receptor antagonist, attenuated the mesencephalic locomotor region-induced suppression of dorsal horn neurons responding to group III afferent input from the hindlimb. Our findings raise the possibility that GABA release onto dorsal horn neurons in the spinal cord may play an important role in the attenuation of the exercise pressor reflex by central command during exercise.
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Affiliation(s)
- Alexandr M Degtyarenko
- Division of Cardiovascular Medicine, Department of Internal Medicine and Human Physiology, University of California, 1 Shields Avenue, Davis, CA 95616, USA.
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Ruscheweyh R, Sandkühler J. Differential actions of spinal analgesics on mono-versus polysynaptic Adelta-fibre-evoked field potentials in superficial spinal dorsal horn in vitro. Pain 2000; 88:97-108. [PMID: 11098104 DOI: 10.1016/s0304-3959(00)00325-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Processing of nociceptive information can be modulated at various levels in spinal cord that may range from changes of neurotransmitter release from primary afferent Adelta- or C-fibres to excitability changes of spinal interneurones or motoneurones. The site and mechanism of action of spinal analgesics has been assessed with a number of in vivo and in vitro methods with sometimes conflicting results. Here, we have used transverse spinal cord slices with attached dorsal roots to simultaneously record mono- and polysynaptic Adelta-fibre-evoked field potentials in superficial spinal dorsal horn. Two classical spinal analgesics, morphine and clonidine, and the metabotropic glutamate receptor agonist (IS,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD) differentially affected mono- and polysynaptic Adelta-fibre-evoked transmission in spinal dorsal horn. Polysynaptic responses were dose-dependently inhibited while the monosynaptic response remained unaffected. These results suggest that spinal analgesics may preferentially affect polysynaptic but not monosynaptic Adelta-fibre-evoked responses in superficial spinal dorsal horn.
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Affiliation(s)
- Ruth Ruscheweyh
- Institute of Physiology and Pathophysiology, Heidelberg University, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
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Degtyarenko AM, Kaufman MP. Fictive locomotion and scratching inhibit dorsal horn neurons receiving thin fiber afferent input. Am J Physiol Regul Integr Comp Physiol 2000; 279:R394-403. [PMID: 10938225 DOI: 10.1152/ajpregu.2000.279.2.r394] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In decerebrate paralyzed cats, we examined the effects of two central motor commands (fictive locomotion and scratching) on the discharge of dorsal horn neurons receiving input from group III and IV tibial nerve afferents. We recorded the impulse activity of 74 dorsal horn neurons, each of which received group III input from the tibial nerve. Electrical stimulation of the mesencephalic locomotor region (MLR), which evoked fictive static contraction or fictive locomotion, inhibited the discharge of 44 of the 64 dorsal horn neurons tested. The mean depth from the dorsal surface of the spinal cord of the 44 neurons whose discharge was inhibited by MLR stimulation was 1.77 +/- 0.04 mm. Fictive scratching, evoked by topical application of bicuculline to the cervical spinal cord and irritation of the ear, inhibited the discharge of 22 of the 29 dorsal horn neurons tested. Fourteen of the twenty-two neurons whose discharge was inhibited by fictive scratching were found to be inhibited by MLR stimulation as well. The mean depth from the dorsal surface of the cord of the 22 neurons whose discharge was inhibited by fictive scratching was 1.77 +/- 0.06 mm. Stimulation of the MLR or the elicitation of fictive scratching had no effect on the activity of 22 dorsal horn neurons receiving input from group III and IV tibial nerve afferents. The mean depth from the dorsal surface of the cord was 1.17 +/- 0.07 mm, a value that was significantly (P < 0.05) less than that for the neurons whose discharge was inhibited by either MLR stimulation or fictive scratching. We conclude that centrally evoked motor commands can inhibit the discharge of dorsal horn neurons receiving thin fiber input from the periphery.
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Affiliation(s)
- A M Degtyarenko
- Division of Cardiovascular Medicine, Departments of Internal Medicine and Human Physiology, University of California, Davis 95616, USA
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McNally GP. Pain facilitatory circuits in the mammalian central nervous system: their behavioral significance and role in morphine analgesic tolerance. Neurosci Biobehav Rev 1999; 23:1059-78. [PMID: 10643817 DOI: 10.1016/s0149-7634(99)00040-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Sensitivity to noxious stimulation is not invariant; rather, it is modulated by discrete pain inhibitory and facilitatory circuits. This paper reviews the neural circuits for pain facilitation, describes the conditions governing their environmental activation, and examines their role in an animal's behavioral repertoire. Mechanisms for pain facilitation are contrasted at both the neural and behavioral level with mechanisms for pain inhibition. In addition, the involvement of mechanisms for pain facilitation in morphine analgesic tolerance is discussed, and the implications of this involvement for accounts of the role of associative processes in analgesic tolerance are highlighted.
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Affiliation(s)
- G P McNally
- Mental Health Research Institute, University of Michigan, Ann Arbor 48109-0720, USA.
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Andrianov GN, Ryzhova IV. Opioid peptides as possible neuromodulators of the afferent synaptic transmission in the frog semicircular canal. Neuroscience 1999; 93:801-6. [PMID: 10465463 DOI: 10.1016/s0306-4522(99)00159-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Vestibular receptors of the frog, Rana temporaria, were examined for the effect of bath-applied opioid peptide leu-enkephalin, its synthetic analogue dalargin and the specific opiate antagonist naloxone. Multiunit afferent activity of the whole vestibular nerve was recorded in an in vitro preparation. Leu-enkephalin (0.005-100 nM) and dalargin (0.1-100 nM) depress the resting discharge frequency. Naloxone (10 nM-1 microM) antagonizes responses induced by leu-enkephalin and dalargin that suggests a specific action of opioid peptides. Leu-enkephalin and delargin inhibit the excitatory action of L-glutamate. The effects of opioid peptides on L-glutamate-induced responses are unaffected by Co2+ block of transmitter release from hair cells that could speak in favour of the postsynaptic nature of these responses. At the same time, the other possible site of action of opioid peptides, such as efferent system, can not be excluded. The results indicate that opiate receptors are present in hair cells and that the neurotransmitter L-glutamate is involved in opiate action at the peripheral vestibular system of the frog. We suggest that opioid peptides may act as a neuromodulator in this system.
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Affiliation(s)
- G N Andrianov
- Laboratory of Physiology of Reception, Pavlov Institute of Physiology, Russian Academy of Sciences, St Petersburg
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mu-Opioid receptors are localized to extrasynaptic plasma membranes of GABAergic neurons and their targets in the rat nucleus accumbens. J Neurosci 1999. [PMID: 9065518 DOI: 10.1523/jneurosci.17-07-02585.1997] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The activation of mu-opioid receptors in the nucleus accumbens (Acb) produces changes in locomotor and rewarding responses that are believed to involve neurons, including local gamma-aminobutyric acid (GABA)ergic neurons. We combined immunogold-silver detection of an antipeptide antiserum against the cloned mu-opioid receptor (MOR) and immunoperoxidase labeling of an antibody against GABA to determine the cellular basis for the proposed opioid modulation of GABAergic neurons in the rat Acb. MOR-like immunoreactivity (MOR-LI) was localized prominently to plasma membranes of neurons having morphological features of both spiny and aspiny cells, many of which contained GABA. Of 351 examples of profiles that contained MOR-LI and GABA labeling, 65% were dendrites. In these dendrites, MOR-LI was seen mainly along extrasynaptic portions of the plasma membrane apposed to unlabeled terminals and/or glial processes. Dually labeled dendrites often received convergent input from GABAergic terminals and/or from unlabeled terminals forming asymmetric excitatory-type synapses. Of all profiles that contained both MOR and GABA immunoreactivity, 28% were axon terminals. MOR-containing GABAergic terminals and terminals separately labeled for MOR or GABA formed synapses with unlabeled dendrites and also with dendrites containing MOR or GABA. Our results indicate that MOR agonists could modulate the activity of GABA neurons in the Acb via receptors located mainly at extrasynaptic sites on dendritic plasma membranes. MOR ligands also could alter the release of GABA onto target dendrites that contain GABA and/or respond to opiate stimulation.
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Xi MC, Liu RH, Yamuy J, Morales FR, Chase MH. Naloxone reduces the amplitude of IPSPs evoked in lumbar motoneurons by reticular stimulation during carbachol-induced motor inhibition. Brain Res 1999; 819:155-9. [PMID: 10082872 DOI: 10.1016/s0006-8993(98)01299-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
During active sleep or carbachol-induced motor inhibition, electrical stimulation of the medullary nucleus reticularis gigantocellularis (NRGc) evoked large amplitude, glycinergic inhibitory postsynaptic potentials (IPSPs) in cat motoneurons. The present study was directed to determine whether these IPSPs, that are specific to the state of active sleep, are modulated by opioid peptides. Accordingly, intracellular recordings were obtained from lumbar motoneurons of acute decerebrate cats during carbachol-induced motor inhibition while an opiate receptor antagonist, naloxone, was microiontophoretically released next to the recorded cells. Naloxone reversibly reduced by 26% the mean amplitude of NRGc-evoked IPSPs (1.9+/-0.2 mV (S.E.M.) vs. 1.4+/-0.2 mV; n=11, control and naloxone, respectively, p<0.05), but had no effect on the other waveform parameters of these IPSPs (e.g., latency-to-onset, latency-to-peak, duration, etc.). The mean resting membrane potential, input resistance and membrane time constant of motoneurons following naloxone ejection were not statistically different from those of the control. These data indicate that opioid peptides have a modulatory effect on NRGc-evoked IPSPs during carbachol-induced motor inhibition. We therefore suggest that endogenous opioid peptides may act as neuromodulators to regulate inhibitory glycinergic synaptic transmission at motoneurons during active sleep.
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Affiliation(s)
- M C Xi
- Department of Physiology and the Brain Research Institute, UCLA School of Medicine, University of California, Los Angeles, CA 90095, USA
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Ma W, Ribeiro-da-Silva A, De Koninck Y, Radhakrishnan V, Cuello AC, Henry JL. Substance P and enkephalin immunoreactivities in axonal boutons presynaptic to physiologically identified dorsal horn neurons. An ultrastructural multiple-labelling study in the cat. Neuroscience 1997; 77:793-811. [PMID: 9070753 DOI: 10.1016/s0306-4522(96)00510-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A combination of intracellular electrophysiological recording and injection of horseradish peroxidase with ultrastructural immunocytochemistry was used to investigate the synaptic interplay between substance P- and enkephalin-immunoreactive axonal boutons and three types of functionally characterized dorsal horn neurons in the cat spinal cord. The dorsal horn neurons were classified as nociceptive specific, wide dynamic range and non-nociceptive based on their responses to innocuous and noxious stimuli. Most of the nociceptive neurons (either nociceptive specific or wide dynamic range) contained enkephalin immunoreactivity, but none of the non-nociceptive neurons were positive for enkephalin. Three types of immunoreactive boutons were found in contact with the functionally characterized dorsal horn neurons. These boutons were positive for either substance P, enkephalin, or substance P+enkephalin. Quantitative analysis revealed that the percentages of substance P-immunoreactive boutons apposed to the cell bodies, proximal dendrites and distal dendrites of nociceptive neurons were significantly higher than those of non-nociceptive neurons. Furthermore, the percentages of substance P+enkephalin-immunoreactive axonal boutons apposed to the distal dendrites of nociceptive neurons were significantly higher than those of non-nociceptive neurons and the percentages of enkephalin-immunoreactive boutons apposed to the cell bodies and proximal dendrites of nociceptive neurons were significantly higher than in non-nociceptive neurons. Finally, neither enkephalin-immunoreactive nor substance P+enkephalin-immunoreactive boutons were ever seen presynaptic to substance P-immunoreactive boutons. These results provide evidence of an anatomical substrate within the dorsal horn for the interaction of substance P-mediated with enkephalin-mediated mechanisms. The data support the idea that the modulation of nociceptive input in the dorsal horn by enkephalinergic neurons occurs mainly via a postsynaptic mechanism, and thus suggest that dorsal horn enkephalinergic neurons participate in a local inhibitory feedback loop in a distinct pathway from the previously postulated opioid-mediated depression of substance P release from primary afferent terminals.
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Affiliation(s)
- W Ma
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
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Abstract
Opiates by an action at specific receptors can induce a highly selective alteration in the response of humans and animals to strong and otherwise aversive chemical, mechanical or thermal stimuli. Specific investigations in a variety of species from rodent to primate using microinjection techniques to examine the pharmacology of local drug action have shown potent antinociceptive actions to be mediated by a receptor specific action at a number of sites within the brain, including the periaqueductal gray (PAG: mu receptor), the rostral ventral medulla (mu/delta receptor) and the substantia nigra (mu receptor) and within the spinal dorsal horn (mu/delta/kappa receptor). Mechanistic studies have shown these actions in the different sites to be mediated by several discrete mechanisms. For example, in the PAG, the local opiate effect is likely mediated by the indirect activation of bulbospinal pathways, rostral projections to forebrain sites and by a local alteration in afferent input into the brainstem core. In the spinal cord, this effect is mediated by an action presynaptic to the primary afferent and by a post-synaptic effect to hyperpolarize projection neurons. In addition, it is now appreciated that mu and kappa receptors in the periphery can modulate the sensitized state of the small afferent terminal innervating inflamed tissue and exert an anti-hyperalgesic action. After systemic delivery of an opiate, it is thus clear that a wide array of central and peripheral systems serve to explain the powerful analgesic effect exerted by this class of agents.
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Affiliation(s)
- T L Yaksh
- Anesthesiology Research Laboratory, University of California, San Diego, USA
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Meintjes AF, Nóbrega AC, Fuchs IE, Ally A, Wilson LB. Attenuation of the exercise pressor reflex. Effect of opioid agonist on substance P release in L-7 dorsal horn of cats. Circ Res 1995; 77:326-34. [PMID: 7542180 DOI: 10.1161/01.res.77.2.326] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Using alpha-chloralose-anesthetized cats, we studied blood pressure and heart rate responses to static contraction and passive stretch of the triceps surae muscle before and after microdialyzing the mu-opioid agonist [D-Ala2]-methionine enkephalinamide (DAME, 200 mumol/L) into the L-7 dorsal horn of the spinal cord. In addition, we measured contraction-induced substance P release in the dorsal horn before and after drug delivery. After 92 +/- 3 minutes of dialyzing the opioid agonist, contraction-induced increases in mean arterial pressure and heart rate were attenuated from control values of 58 +/- 7 mm Hg and 17 +/- 3 beats per minute to postdrug values of 27 +/- 7 mm Hg and 10 +/- 2 beats per minute, respectively. A similar attenuation was observed for the passive muscle stretches after 97 +/- 5 minutes of dialysis (control, 38 +/- 4 mm Hg and 8 +/- 2 beats per minute; after drug, 23 +/- 4 mm Hg and 5 +/- 1 beats per minute). Prior microdialysis of naloxone (300 mumol/L), a mu-antagonist, blocked this effect, suggesting that the opioid agonist has a specific receptor action. Naloxone alone had no effect on the pressor or tachycardiac responses. The contraction-induced increase in substance P-like immunoreactivity was reduced from a control value of 0.119 +/- 0.024 to 0.047 +/- 0.010 fmol/100 microL by DAME. Time-control experiments revealed no decrease in the release of substance P-like immunoreactivity. Thus, activation of opioid receptors modulates the transmission of group III and IV muscle afferent nerve activity through the L-7 dorsal horn.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A F Meintjes
- Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, USA
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Mao J, Price DD, Phillips LL, Lu J, Mayer DJ. Increases in protein kinase C gamma immunoreactivity in the spinal cord of rats associated with tolerance to the analgesic effects of morphine. Brain Res 1995; 677:257-67. [PMID: 7552251 DOI: 10.1016/0006-8993(95)00161-i] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Our previous studies have indicated a critical role of protein kinase C (PKC) in intracellular mechanisms of tolerance to morphine analgesia. In the present experiments, we examined (1) the cellular distribution of a PKC isoform (PKC gamma) in the spinal cord dorsal horn of rats associated with morphine tolerance by utilizing an immunocytochemical method and (2) the effects of the N-methyl-D-aspartate receptor antagonist MK-801 on tolerance-associated PKC gamma changes. In association with the development of tolerance to morphine analgesia induced by once daily intrathecal administration of 10 micrograms morphine for eight days, PKC gamma immunoreactivity was clearly increased in the spinal cord dorsal horn of these same rats. Within the spinal cord dorsal horn of morphine tolerant rats, there were significantly more PKC gamma immunostained neurons in laminae I-II than in laminae III-IV and V-VI. Such PKC gamma immunostaining was observed primarily in neuronal somata indicating a postsynaptic site of PKC gamma increases. Moreover, both the development of morphine tolerance and the increase in PKC gamma immunoreactivity were prevented by co-administration of morphine with 10 nmol MK-801 between Day 2 and Day 7 of the eight day treatment schedule. In contrast, PKC gamma immunoreactivity was not increased in rats receiving a single i.t. administration of 10 micrograms morphine on Day 8, nor did repeated treatment with 10 nmol MK-801 alone change baseline levels of PKC gamma immunoreactivity. These results provide further evidence for the involvement of PKC in NMDA receptor-mediated mechanisms of morphine tolerance.
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Affiliation(s)
- J Mao
- Department of Anesthesiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0516, USA
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Jaffe RA, Rowe MA. Subanesthetic concentrations of lidocaine selectively inhibit a nociceptive response in the isolated rat spinal cord. Pain 1995; 60:167-174. [PMID: 7784102 DOI: 10.1016/0304-3959(94)00117-w] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Systemically administered local anesthetics are known to provide analgesia in a variety of pain states; however, the site of action and the mechanism by which these effects are produced remain in question. In the present study, the effects of low (subblocking for nerve conduction) concentrations of lidocaine on a spinal cord nociceptive potential were studied. Spinal cords were removed from neonatal rats and maintained in vitro. Lumbar dorsal and ipsilateral ventral roots were attached to suction electrodes for stimulation and recording, respectively. Following a stabilization period (60-120 min) with control measurements, each preparation was exposed to a single concentration of lidocaine (30-60 min) then returned to control perfusate for recovery (60-120 min). Data were digitized and integrals computed for both monosynaptic and slow ventral root potentials (VRP). Low concentrations of lidocaine produced a selective reduction in the magnitude of the slow-VRP. At lidocaine concentrations of 1-10 micrograms/ml (3.6-36 microM), the slow-VRP was reduced from 79% to 36% of control. Recovery to pre-exposure control levels was slow and sometimes not complete after 60-120 min in drug-free perfusate. The monosynaptic component of the VRP was unaffected by lidocaine at any concentration, suggesting that the depression of the slow-VRP cannot be attributed to simple conduction block. The addition of naloxone 0.1 microM to the perfusate had minimal effect on lidocaine-induced depression. Although resembling the selective effects of morphine, the antinociceptive effects of lidocaine do not appear to be primarily mediated through opiate receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- Richard A Jaffe
- Department of Anesthesia, Stanford University School of Medicine, Stanford, CA 94305 USA
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Sivilotti LG, Gerber G, Rawat B, Woolf CJ. Morphine selectively depresses the slowest, NMDA-independent component of C-fibre-evoked synaptic activity in the rat spinal cord in vitro. Eur J Neurosci 1995; 7:12-8. [PMID: 7711929 DOI: 10.1111/j.1460-9568.1995.tb01015.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of morphine on the depolarizing synaptic responses produced in motoneurons by electrical stimulation of primary sensory neurones have been recorded in hemisected spinal cord preparations (8- to 12-day-old rat pups). Morphine at concentrations of 0.1-20 microM reduced a slow, long-lasting (latency greater than 1 s, duration up to 10 s) component of the ventral root potential (VRP) evoked by C-fibre strength stimulation of the dorsal root. At 2 microM the reduction in area of this slow synaptic potential was 71.7 +/- 0.9% of control values (n = 15). The earliest components of the C-fibre strength VRP (the first 100 ms) and the responses to A beta strength stimuli were unaffected by the opioid even at 10-20 microM. The intermediate, NMDA receptor antagonist (D-AP5, 40 microM)-sensitive component (which lasts 100-1000 ms) was reduced by 34 +/- 2.2% of control (n = 15), which was significantly less than the reduction of the later NMDA-independent component (P < 0.001). Morphine (0.1-20 microM) also depressed the cumulative depolarization generated by the temporal summation of synaptic responses evoked by brief trains of C-fibre strength stimuli (1 or 10 Hz). A significantly greater reduction at the lower frequency of stimulation (56.3 +/- 2.0%) than at the higher (20.3 +/- 1.69%, n = 10, measured at 2 microM morphine) was found (P < 0.005). The effects of morphine were reversible upon wash-out or superfusion with the opioid receptor antagonist naloxone (2 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L G Sivilotti
- Department of Anatomy and Developmental Biology, University College London, UK
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Randić M, Kolaj M, Kojić L, Cerne R, Cheng G, Wang RA. Interaction of neuropeptides and excitatory amino acids in the rat superficial spinal dorsal horn. PROGRESS IN BRAIN RESEARCH 1995; 104:225-53. [PMID: 8552771 DOI: 10.1016/s0079-6123(08)61793-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- M Randić
- Department of Veterinary Physiology and Pharmacology, Iowa State University, Ames 50011, USA
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40
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Brennum J, Petersen KL, Horn A, Arendt-Nielsen L, Secher NH, Jensen TS. Quantitative sensory examination of epidural anaesthesia and analgesia in man: combination of morphine and bupivacaine. Pain 1994; 56:327-337. [PMID: 8022626 DOI: 10.1016/0304-3959(94)90171-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effect of epidural administration of a combination of low-dose morphine (2 mg) and bupivacaine (25 mg) on somatosensory and motor functions was examined in 13 healthy volunteers. The study design was a double-blind 4-way cross-over in which combined treatment was compared with either drug used alone or placebo. Every 2nd hour for 10 h effects on nociceptive and non-nociceptive somatosensory functions were quantified with 12 psychophysical measures. In addition knee extension strength, reaction time and skin temperature were examined. Epidural bupivacaine had hypoalgesic effect in all nociceptive tests, whereas epidural morphine only demonstrated hypoalgesic properties in nociceptive test with prolonged stimuli. In comparison with bupivacaine alone the combination treatment had a lesser peak effect but a more prolonged hypoalgesic action. In comparison with morphine alone the combination treatment induced a faster onset and demonstrated a modest increase in hypoalgesic effect in a subset of the test, even beyond the duration of bupivacaine when administered alone. Motor function was not attenuated by any of the treatments. Mechanisms of interaction between morphine and bupivacaine as well as their possible clinical implications are discussed.
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Affiliation(s)
- Jannick Brennum
- Laboratory of Sensory Physiology, Department of Neurology, Gentofte Hospital, DK-2900 HellerupDenmark Department of Anaesthesia, Rigshospitalet, DK-2100 København ØDenmark Department of Medical Informatics, Aalborg University, DK-9100 AalborgDenmark Department of Neurology, Aarhus University Hospital, DK-8000 Aarhus CDenmark
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Smith GD, Harrison SM, Wiseman J, Elliott PJ, Birch PJ. Pre-emptive administration of clonidine prevents development of hyperalgesia to mechanical stimuli in a model of mononeuropathy in the rat. Brain Res 1993; 632:16-20. [PMID: 8149225 DOI: 10.1016/0006-8993(93)91132-c] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Traumatic nerve injury in man can often result in the development of neuropathy. An animal model of neuropathic hyperalgesia is produced by loose ligation of the sciatic nerve in the rat. We have examined the effect of pre-emptive treatment with a number of drugs on the development of hyperalgesia in this model. Animals received clonidine (1 mg.kg-1, s.c.), morphine (5 mg.kg-1, s.c.), (+/-)-baclofen (40 mg.kg-1, s.c.), carbamazepine (50 mg.kg-1, s.c.) or vehicle (4 ml.kg-1, s.c.) 30 min prior to loose ligation or sham-operation. Morphine- and clonidine-treated animals were administered a second dose of drug 6h following surgery. Twenty-six or twenty-nine days following surgery, the ipsilateral (ipsi.) and contralateral (contra.) paw withdrawal thresholds were determined using an Algesymeter. In vehicle-treated animals the ipsilateral paw withdrawal threshold (118 +/- 7 g) was significantly lower (P < 0.0001, paired t-test) than the contralateral (195 +/- 7 g). In contrast, in animals pre-treated with clonidine no significant difference between ipsilateral (200 +/- 9 g) and contralateral (191 +/- 7 g) paw withdrawal thresholds was detected. Morphine pre-treatment was less effective in preventing development of hyperalgesia; however, whilst the ipsilateral (146 +/- 18 g) paw withdrawal threshold tended to be lower than the contralateral (183 +/- 8 g), this was not significant.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G D Smith
- Department of Gastrointestinal Pharmacology, Glaxo Group Research, Ware, Herts, UK
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Zhuo H, Fung SJ, Barnes CD. Opioid action on spinal cord reflexes due to dorsolateral pontine tegmentum stimulation. Neuropharmacology 1993; 32:621-31. [PMID: 8361578 DOI: 10.1016/0028-3908(93)90075-e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Electrical stimulation of the dorsolateral pontine tegmentum (DLPT) produces phasic facilitatory and inhibitory actions on the lumbar spinal monosynaptic reflexes (MSRs) of both flexor and extensor muscle nerves in the decerebrate cat. Naloxone, an opioid receptor antagonist, given intravenously or intraspinally enhanced the DLPT-induced potentiation of MSRs in most of the reflexes studied. However, systemic naloxone had no significant effect on the unconditioned MSR of the spinal cord. Intraspinal microinjections of naloxone significantly attenuated the DLPT-induced inhibition of MSRs of both flexors and extensors, similar to the action of systemic injection of naloxone, indicating a direct opioid action at the spinal ventral horn level upon DLPT stimulation. Results of the present experiment further support the anatomical finding that there are pontospinal enkephalinergic pathways in the cat, and indicate that these descending pathways modulate spinal motor outflow.
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Affiliation(s)
- H Zhuo
- Department of VCAPP, Washington State University, Pullman 99164-6520
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Effect of dalargin, a synthetic leu-enkephalin analogue on synaptic transmission in the Lorenzini ampullae of rays. NEUROPHYSIOLOGY+ 1993. [DOI: 10.1007/bf01053627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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44
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Yuan XR, Madamba S, Siggins GR. Opioid peptides reduce synaptic transmission in the nucleus accumbens. Neurosci Lett 1992; 134:223-8. [PMID: 1317025 DOI: 10.1016/0304-3940(92)90522-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Behavioral studies implicate the nucleus accumbens (NAcc) as a brain area pivotal for the rewarding effects of opiates like heroine and morphine. Therefore, we studied the effect of a variety of opioids on membrane properties and responses to synaptic stimulation in a slice preparation of the NAcc using intracellular recording. Superfusion of opioid peptides did not affect the membrane potential or input resistance of NAcc neurons, but significantly reduced both depolarizing and hyperpolarizing synaptic potentials. Naloxone superfusion significantly reversed the depressant effects of the mu and delta receptor agonists (but not those of the kappa agonist) on synaptic transmission, suggesting involvement of opiate receptors. These results imply that the predominant effect of opiates in NAcc is a reduction of synaptic transmission.
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Affiliation(s)
- X R Yuan
- Department of Neuropharmacology, Scripps Research Institute, La Jolla, CA
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45
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Dong XW, Parsons CG, Headley PM. Effects of intravenous mu and kappa opioid receptor agonists on sensory responses of convergent neurones in the dorsal horn of spinalized rats. Br J Pharmacol 1991; 103:1230-6. [PMID: 1652344 PMCID: PMC1908083 DOI: 10.1111/j.1476-5381.1991.tb12329.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
1. Electrophysiological experiments have been performed to assess the effects of intravenously administered mu and kappa opioid agonists on the responses to noxious thermal and mechanical and non-noxious tactile stimuli of single convergent neurones in laminae III-VI of the dorsal horn of spinalized rats anaesthetized with alpha-chloralose. 2. The mu receptor agonists tested were fentanyl (1-16 micrograms kg-1) and morphine (0.5-16 mg kg-1) and the kappa-receptor agonists U-50,488 (1-16 mg kg-1) and tifluadom (0.1-1.6 mg kg-1). Multiple drug tests were made on each cell so that compounds could be compared under closely comparable conditions. 3. In one protocol, thermal and mechanical nociceptive responses of matched amplitudes were elicited alternately. Both mu and kappa agonists dose-dependently reduce the neuronal responses. Thermal nociceptive responses were as sensitive to the kappa agents as were the mechanical nociceptive responses; the mu agonists similarly reduced both types of response in parallel. 4. In another protocol, nociceptive and non-nociceptive responses were elicited alternately to permit the degree of selective antinociception to be assessed. The mu agonists were scarcely selective, fentanyl reducing nociceptive only slightly (but significantly at 4-16 micrograms kg-1) more than non-nociceptive responses. The kappa-opioid agonist U50,488 reduced tactile responses somewhat more than nociceptive responses. 5. The spontaneous discharge of these cells with ongoing activity was reduced to a significantly greater degree than the evoked responses; this is likely to have contributed to the non-selectivity of the reduction of the evoked responses. 6. The results are discussed with respect firstly to previous reports that K opioids are ineffective in tests of thermal nociception, and secondly to the likely spinal mechanisms by which opioid receptor agonists mediate antinociception.
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Affiliation(s)
- X W Dong
- Department of Physiology, School of Medical Sciences, University of Bristol
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46
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Hao XJ, Xu JX, Aldskogius H, Seiger Å, Wiesenfeld-Hallin Z. Allodynia-like effects in rat after ischaemic spinal cord injury photochemically induced by laser irradiation. Pain 1991; 45:175-185. [PMID: 1652116 DOI: 10.1016/0304-3959(91)90186-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We report behaviours suggesting the presence of allodynia elicited by non-noxious brushing and mechanical pressure following photochemically induced ischaemic spinal cord injury in the rat. Female rats were intravenously injected with Erythrosin B and the T10 vertebra was irradiated with a laser beam for 1, 5 or 10 min. These procedures initiated an intravascular photochemical reaction, resulting in ischaemic spinal cord injury. After irradiation a clear allodynia was observed in most rats. The animals vocalized intensely to light touch during gentle handling and were clearly agitated to light brushing of the flanks. The vocalization threshold in response to the mechanical pressure measured with von Frey hairs was markedly decreased during this period. In some animals the existence of spontaneous pain was suggested by spontaneous vocalization. The duration of the allodynia varied among animals from several hours to several days. The severity and duration of allodynia seemed not to be related to the duration of irradiation. In sham-operated rats a slight, transient allodynia was also noted around the wound within a few hours after surgery, which was effectively relieved by systemic morphine (2 mg/kg, i.p.). Morphine (2 mg/kg, i.p.) also partially relieved the allodynia in spinally injured rats 4 h after irradiation. However, morphine, even at a higher dose (5 mg/kg, i.p.), failed to alleviate the allodynia in spinally injured rats 24-48 h after the injury. Systemic injection of the GABAB agonist baclofen (0.01-0.1 mg/kg, i.p.), but not the GABAA agonist muscimol (1 mg/kg, i.p.), effectively relieved allodynia during this period. Pretreatment with guanethidine 24 h and just prior to the irradiation (20 mg/kg, s.c.) did not prevent the occurrence of allodynia in spinal cord injured rats. The present observation is the first to show that ischaemic spinal cord injury could result in cutaneous mechanical allodynia. This phenomenon is resistant to morphine and may not involve the sympathetic system. Histological examination of allodynic animals 3 days after spinal cord injury revealed considerable morphological damage in the dorsal spinal cord of a rat irradiated for 5 min. The related dorsal roots were also slightly affected in this animal, while the dorsal root ganglia were normal. However, in rats irradiated for 1 min, despite the existence of strong allodynia, no damage could be found at this time in the spinal cord, dorsal roots or dorsal root ganglia. It is suggested that functional deficits in the GABAB system in the spinal cord may be related to this allodynia-like phenomenon.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- X J Hao
- Department of Clinical Physiology, Section of Clinical Neurophysiology, Karolinska Institute, HuddingeSweden Department of Anatomy, Karolinska Institute, StockholmSweden Department of Geriatric Medicine, Karolinska Institute, HuddingeSweden
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47
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Hao JX, Wiesenfeld-Hallin Z, Xu XJ. Depression of the flexor reflex by systemic morphine increases in chronically spinalized rats. Eur J Pharmacol 1990; 191:407-16. [PMID: 2086250 DOI: 10.1016/0014-2999(90)94175-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effect of i.v. morphine on the spinal nociceptive flexor reflex was examined in decerebrate, unanesthetized rats in which the spinal cord was acutely or chronically transected. In acutely spinalized rats i.v. morphine dose dependently depressed the flexor reflex with an ED50 of 1.4 mg/kg. In rats in which the spinal cord was transected 1-3 days prior to the electrophysiological experiments, i.v. morphine had a similar depressive effect (ED50 = 1.1 mg/kg). However, 4-6 days after spinalization there was a 4-fold increase in morphine's depressive effect (ED50 = 0.35 mg/kg). The sensitivity to morphine was further increased 7-10 days post-spinalization with ED50 of 0.17 mg/kg. This supersensitivity was maintained up to 30-60 days. The reflex depression caused by morphine in both acutely and chronically spinalized rats could be reversed by naloxone. Morphine i.v. did not influence the monosynaptic reflex in either acutely or chronically spinalized rats. The present results support the clinical finding that patients with spinal lesions have an increased sensitivity to the antinociceptive and reflex depressive effects of systemic and intrathecal morphine.
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Affiliation(s)
- J X Hao
- Department of Clinical Physiology, Karolinska Institute, Huddinge, Sweden
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48
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Jones SL, Sedivec MJ, Light AR. Effects of iontophoresed opioids on physiologically characterized laminae I and II dorsal horn neurons in the cat spinal cord. Brain Res 1990; 532:160-74. [PMID: 2282511 DOI: 10.1016/0006-8993(90)91756-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The objective of the present study was to determine in vivo the effects of opioids applied locally via microiontophoresis on physiologically characterized laminae I and II dorsal horn neurons in the cat spinal cord. Experiments were performed on pentobarbital-anesthetized or decerebrate, spinalized cats. The effects of morphine (MOR), [D-Ala2,methyl-Phe4, Gly-ol5]enkephalin (DAGO) and naloxone (NALO) on spontaneous- and D,L-homocysteic acid-evoked unit activity were examined for 94 laminae I and II dorsal horn neurons. MOR, DAGO and NALO produced mixed effects (i.e., excitation or inhibition) on unit activity; however, the majority of cells examined (67%) were inhibited. Whether MOR, DAGO or NALO exerted excitatory or inhibitory influences on unit activity did not depend on the modality of the neuron (66% of high threshold units, 56% of multireceptive units and 69% of low threshold units were inhibited; some cells of each modality also were excited). NALO also was found rarely to be neutral; 75% of the cells examined were inhibited and 16% excited by NALO. Since NALO was found to itself have significant effects on laminae I and II dorsal horn unit activity, the ability to use NALO as an opioid antagonist to MOR and DAGO was confounded.
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Affiliation(s)
- S L Jones
- Department of Pharmacology, College of Medicine, University of Oklahoma, Oklahoma City 73190
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Hope PJ, Fleetwood-Walker SM, Mitchell R. Distinct antinociceptive actions mediated by different opioid receptors in the region of lamina I and laminae III-V of the dorsal horn of the rat. Br J Pharmacol 1990; 101:477-83. [PMID: 2175238 PMCID: PMC1917709 DOI: 10.1111/j.1476-5381.1990.tb12733.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
1. In view of the presence of mu, delta and kappa opioid receptors in the spinal dorsal horn and their apparent involvement in behavioural analgesia, the present experiments addressed the action of selective agonists ionophoresed in the vicinity of rat dorsal horn neurones which were located either in lamina I or in laminae III-V. 2. In laminae III-V, kappa agonists (U50488H and dynorphin A) caused a selective inhibition of the nociceptive responses of multireceptive cells, whilst mu and delta agonists [( D-Ala2, MePhe4, Gly-ol]enkephalin and [D-Pen2, D-Pen5]enkephalin respectively) failed to alter either the spontaneous activity or the response to noxious and innocuous cutaneous stimuli and to D,L-homocysteic acid or glutamate. Nocispecific neurones were encountered too rarely in laminae III-V to study their properties. 3. In lamina I, agonists had no effects on either nocispecific or multireceptive neurones. In contrast, the mu agonist [D-Ala2, MePhe4, Gly-ol]enkephalin consistently inhibited nociceptive responses of both multireceptive and nocispecific lamina I cells. The delta agonist [D-Pen2, D-Pen5]enkephalin consistently caused selective inhibition of the nociceptive responses of multireceptive cells but had a mixed profile of action on nocispecific cells. 4. These results suggest that mu, delta and kappa opioid receptors mediate different antinociceptive actions in both laminae III-V and lamina I. The study reveals a distinct physiological role for delta receptors in modulating nociceptive inputs to lamina I neurones. In contrast to mu and kappa receptor actions, delta receptors heterogeneously influence subpopulations of neurones.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
- Analgesics/pharmacology
- Animals
- Electric Stimulation
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalin, D-Penicillamine (2,5)-
- Enkephalins/pharmacology
- Neurons/drug effects
- Pain/physiopathology
- Pyrrolidines/pharmacology
- Rats
- Receptors, Opioid/drug effects
- Receptors, Opioid/physiology
- Receptors, Opioid, delta
- Receptors, Opioid, kappa
- Receptors, Opioid, mu
- Spinal Cord/physiology
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Affiliation(s)
- P J Hope
- Department of Preclinical Veterinary Sciences, University of Edinburgh
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Kellstein DE, Price DD, Hayes RL, Mayer DJ. Evidence that substance P selectively modulates C-fiber-evoked discharges of dorsal horn nociceptive neurons. Brain Res 1990; 526:291-8. [PMID: 1701684 DOI: 10.1016/0006-8993(90)91234-8] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Previous studies suggest that the undecapeptide substance P (SP) functions as a primary afferent neurotransmitter or neuromodulator of nociception which may mediate the slow temporal summation ('windup') of discharges of dorsal horn nociceptive neurons elicited by repetitive stimulation of C-afferents. The present study tested this hypothesis by investigating the effects of local spinal application of SP and an SP antagonist. [D-Pro2,D-Trp7,9]-SP (DPDT), on A- and C-fiber-evoked firing of dorsal horn neurons in an intact, urethane-anesthetized rat preparation. Extracellular single unit recordings from both wide dynamic range and nociceptive specific neurons during controlled repetitive electrical stimulation of the ipsilateral hind paw indicated that SP enhanced C-evoked firing in an apparent dose-related manner (100 greater than 20 = 4 nmol), whereas DPDT inhibited C-evoked discharges with an apparent bell-shaped dose-response (20 greater than 100 = 4 nmol). Neither agent significantly altered either A-evoked or spontaneous activity. In agreement with previous investigators, morphine sulfate also selectively inhibited C-fiber-evoked firing without altering A-fiber-mediated activity, validating the selectivity of our system. These findings provide additional evidence that SP functions as a neuromodulator of primary afferent nociception, and further suggest that the effects of SP are selective to nociceptive transmission mediated by C-fibers.
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Affiliation(s)
- D E Kellstein
- Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond
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