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Wang JY, Bai WZ, Gao YH, Zhang JL, Duanmu CL, Liu JL. GABAergic Inhibition of Spinal Cord Dorsal Horns Contributes to Analgesic Effect of Electroacupuncture in Incisional Neck Pain Rats. J Pain Res 2020; 13:1629-1645. [PMID: 32694919 PMCID: PMC7340366 DOI: 10.2147/jpr.s242330] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 05/23/2020] [Indexed: 11/30/2022] Open
Abstract
Background Acupuncture has shown to be effective in relieving post-surgical pain. Nonetheless, its underlying mechanisms remain largely unknown. In the present study, we investigated the effect of electroacupuncture (EA) on the expression of GABA, GABA-A receptor (R) and GABA-BR in the spinal cord dorsal horns (DHs), and the involved neural cells in rats with incisional neck pain. Materials and Methods Male SD rats were randomly divided into control, model, Futu (LI18), Hegu-Neiguan (LI4-PC6), and Zusanli-Yanglingquan (ST36-GB34) groups. The incisional neck pain model was established by making a longitudinal incision and repeated mechanical separation along the thyroid gland region. EA (2Hz/100Hz, 1mA) was applied to LI18, LI4-PC6, ST36-GB34 separately for 30min, once at 4, 24 and 48h after incision. The local thermal pain threshold (TPT) of the focus was measured and the expression of GABA, and GABAR proteins and mRNAs detected by immunofluorescence stain and quantitative RT-PCR, respectively. Results The analgesic effect of LI18 and LI4-PC6 was superior to that of ST36-GB34 in incisional neck pain rats. Moreover, the EA stimulation of LI18 or LI4-PC6 increased the expression of GABA and GABA-Aα2 and GABA-Aβ3, GABA-B1, and GABA-B2 mRNAs in spinal DHs 4h after surgery, while GABA-A and GABA-B antagonists inhibited the analgesic effect of LI18. Immunofluorescence double staining showed that GABA was expressed on astrocytes and neurons, and GABA-B expressed only on neurons. Conclusion EA of both LI18 and LI4-PC6 has a good analgesic effect in incisional neck pain rats, which is closely related to their effects in upregulating the expression of GABA and its receptors in spinal DHs. The effects of LI18 and LI4-PC6 EA are obviously better that those of ST36-GB34 EA, and GABA is expressed on neurons and astrocytes.
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Affiliation(s)
- Jun-Ying Wang
- Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, People's Republic of China
| | - Wan-Zhu Bai
- Laboratory for Architecture of Acupoints, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, People's Republic of China
| | - Yong-Hui Gao
- Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, People's Republic of China
| | - Jian-Liang Zhang
- Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, People's Republic of China
| | - Cheng-Lin Duanmu
- Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, People's Republic of China
| | - Jun-Ling Liu
- Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, People's Republic of China
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Selective ablation of TRPV1 by intrathecal injection of resiniferatoxin in rats increases renal sympathoexcitatory responses and salt sensitivity. Hypertens Res 2018; 41:679-690. [PMID: 30006640 DOI: 10.1038/s41440-018-0073-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 01/03/2018] [Accepted: 01/09/2018] [Indexed: 01/28/2023]
Abstract
This study tested the hypothesis that selective ablation of transient receptor potential vanilloid type 1 (TRPV1)-positive nerve fibers by intrathecal injection of resiniferatoxin (RTX) enhances renal sympathoexcitatory responses and salt sensitivity. Intrathecal injection of RTX (1.8 μg/kg) to the levels of lower thoracic and upper lumbar spinal cord (T8-L3) increased mean arterial pressure (MAP) in rats fed a normal (NS, 1% NaCl) or high-sodium (HS, 8% NaCl) diet for 4 weeks compared to vehicle-treated rats (NS: 121 ± 2 vs. 111 ± 2; HS: 154 ± 2 vs. 134 ± 2 mm Hg, both P < 0.05), with a greater increase in HS compared to NS rats (9 ± 1% vs. 15 ± 1%, P < 0.05). TRPV1 contents were decreased in T8-L3 segments of spinal dorsal horn but not in corresponding dorsal root ganglia and the kidney following RTX treatment (P < 0.05). Selective activation of GABA-A receptors with intrathecal T8-L3 segment-injection of muscimol (3 nmol/kg) decreased renal sympathetic nerve activity and increased urinary excretion in both NS and HS rats, with a greater effect in RTX-treated compared to vehicle-treated rats (P < 0.05). Chronic activation of GABA-A receptors with muscimol (50 mg/kg/day × 2, p.o.) abolished RTX treatment-induced pressor effects in NS and HS rats. GAD65/67, a GABA synthetase, in the spinal cord was downregulated and tyrosine hydroxylase in the kidney upregulated in NS or HS rats treated with RTX (P < 0.05). Thus, selective ablation of TRPV1-positive central terminals of sensory neurons plays a prohypertensive role possibly via inhibition of spinal GABA system especially with HS intake, suggesting that activation of TRPV1 in central terminals of sensory neurons may convey an antihypertensive effect.
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Wang Y, Pillai S, Wolpaw JR, Chen XY. H-reflex down-conditioning greatly increases the number of identifiable GABAergic interneurons in rat ventral horn. Neurosci Lett 2009; 452:124-9. [PMID: 19383426 DOI: 10.1016/j.neulet.2009.01.054] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 01/15/2009] [Accepted: 01/21/2009] [Indexed: 11/29/2022]
Abstract
H-reflex down-conditioning increases GABAergic terminals on spinal cord motoneurons. To explore the origins of these terminals, we studied the numbers and distributions of spinal cord GABAergic interneurons. The number of identifiable GABAergic interneurons in the ventral horn was 78% greater in rats in which down-conditioning was successful than in naive rats or rats in which down-conditioning failed. No increase occurred in other spinal lamina or on the contralateral side. This finding supports the hypothesis that the corticospinal tract influence that induces the motoneuron plasticity underlying down-conditioning reaches the motoneuron through GABAergic interneurons in the ventral horn.
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Affiliation(s)
- Yu Wang
- Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York, P.O. Box 509, Albany, NY 12201-0509, USA.
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Soril LJ, Ramer LM, McPhail LT, Kaan TK, Ramer MS. Spinal brain-derived neurotrophic factor governs neuroplasticity and recovery from cold-hypersensitivity following dorsal rhizotomy. Pain 2008; 138:98-110. [DOI: 10.1016/j.pain.2007.11.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Revised: 11/07/2007] [Accepted: 11/19/2007] [Indexed: 12/22/2022]
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5
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Pillai S, Wang Y, Wolpaw JR, Chen XY. Effects of H-reflex up-conditioning on GABAergic terminals on rat soleus motoneurons. Eur J Neurosci 2008; 28:668-74. [PMID: 18657184 PMCID: PMC2923547 DOI: 10.1111/j.1460-9568.2008.06370.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
To explore the role of spinal cord plasticity in motor learning, we evaluated the effects of H-reflex operant conditioning on GABAergic input to rat spinal motoneurons. Previous work indicated that down-conditioning of soleus H-reflex increases GABAergic input to soleus motoneurons. This study explored the effect of H-reflex up-conditioning on GABAergic input. Of nine rats exposed to H-reflex up-conditioning, up-conditioning was successful (H-reflex increase >or= 20%) in seven and failed (change < 20%) in two. These rats and eight naive control (i.e. unconditioned) rats were injected with cholera toxin subunit B-conjugated Alexa fluor 488 into the soleus muscle to retrogradely label soleus motoneurons. Sections containing soleus motoneurons were processed for GAD(67) [one of the two principal forms of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD)] with an ABC-peroxidase system. Two blinded independent raters counted and measured GABAergic terminals on these motoneurons. Unlike successful down-conditioning, which greatly increased the number of identifiable GABAergic terminals on the motoneurons, up-conditioning did not significantly change GABAergic terminal number. Successful up-conditioning did produce slight but statistically significant increases in GABAergic terminal diameter and soma coverage. These results are consistent with other data indicating that up- and down-conditioning are not mirror images of each other, but rather have different mechanisms. Although the marked changes in GABAergic terminals with down-conditioning probably contribute to H-reflex decrease, the modest changes in GABAergic terminals associated with up-conditioning may be compensatory or reactive plasticity, rather than the plasticity responsible for H-reflex increase. As a variety of spinal and supraspinal GABAergic neurons innervate motoneurons, the changes found with up-conditioning may be in terminals other than those affected in successful down-conditioning.
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Affiliation(s)
- Shreejith Pillai
- Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health and State University of New York, Albany, NY 12201, USA
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Wang Y, Pillai S, Wolpaw JR, Chen XY. Motor learning changes GABAergic terminals on spinal motoneurons in normal rats. Eur J Neurosci 2006; 23:141-50. [PMID: 16420424 DOI: 10.1111/j.1460-9568.2005.04547.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The role of spinal cord plasticity in motor learning is largely unknown. This study explored the effects of H-reflex operant conditioning, a simple model of motor learning, on GABAergic input to spinal motoneurons in rats. Soleus motoneurons were labeled by retrograde transport of a fluorescent tracer and GABAergic terminals on them were identified by glutamic acid decarboxylase (GAD)67 immunoreactivity. Three groups were studied: (i) rats in which down-conditioning had reduced the H-reflex (successful HRdown rats); (ii) rats in which down-conditioning had not reduced the H-reflex (unsuccessful HRdown rats) and (iii) unconditioned (naive) rats. The number, size and GAD density of GABAergic terminals, and their coverage of the motoneuron, were significantly greater in successful HRdown rats than in unsuccessful HRdown or naive rats. It is likely that these differences are due to modifications in terminals from spinal interneurons in lamina VI-VII and that the increased terminal number, size, GAD density and coverage in successful HRdown rats reflect and convey a corticospinal tract influence that changes motoneuron firing threshold and thereby decreases the H-reflex. GABAergic terminals in spinal cord change after spinal cord transection. The present results demonstrate that such spinal cord plasticity also occurs in intact rats in the course of motor learning and suggest that this plasticity contributes to skill acquisition.
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Affiliation(s)
- Yu Wang
- Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health and State University of New York, PO Box 509, Albany, NY 12201, USA.
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7
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Kleppner SR, Tobin AJ. GABA signalling: therapeutic targets for epilepsy, Parkinson's disease and Huntington's disease. Expert Opin Ther Targets 2005; 5:219-39. [PMID: 15992178 DOI: 10.1517/14728222.5.2.219] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Temporal lobe epilepsy (TLE), Parkinson's disease (PD) and Huntington's disease (HD) are neurodegenerative disorders that involve disruptions in gamma-amino butyric acid (GABA) signalling. GABA is the major inhibitory neurotransmitter in the central nervous system (CNS). TLE seizures reflect excess excitation, which may result from local inhibitory circuit dysfunction. PD devastates the input to striatal GABAergic neurones and HD destroys striatal GABAergic neurones. Controlling GABA delivery to specific brain areas should benefit each of these diseases. The molecules responsible for GABA release and signalling are ideal targets for new therapies. In this paper, we discuss the role of GABA in the circuitry affected by each of these diseases and suggest potential sites for intervention. GABA is unique among neurotransmitters because it can be synthesised by either of two related enzymes. Intracellular GABA is found throughout the cytosol and in synaptic vesicles. GABA can be released either through exocytosis, or via the plasma membrane transporter. The synthesising enzyme probably determines the intracellular location and hence the mechanism for GABA release. Directing GABA synthesis, degradation, transport or receptors can control GABA signalling. We propose that new drugs and devices aimed at GABA synthesis, release and binding will offer novel and highly effective treatments for neurodegenerative diseases.
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Affiliation(s)
- S R Kleppner
- Department of Physiological Science, Brain Research Institute, University of California, Los Angeles, CA 90095-1761, USA.
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8
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Partial peripheral nerve injury promotes a selective loss of GABAergic inhibition in the superficial dorsal horn of the spinal cord. J Neurosci 2002. [PMID: 12151551 DOI: 10.1523/jneurosci.22-15-06724.2002] [Citation(s) in RCA: 565] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To clarify whether inhibitory transmission in the superficial dorsal horn of the spinal cord is reduced after peripheral nerve injury, we have studied synaptic transmission in lamina II neurons of an isolated adult rat spinal cord slice preparation after complete sciatic nerve transection (SNT), chronic constriction injury (CCI), or spared nerve injury (SNI). Fast excitatory transmission remains intact after all three types of nerve injury. In contrast, primary afferent-evoked IPSCs are substantially reduced in incidence, magnitude, and duration after the two partial nerve injuries, CCI and SNI, but not SNT. Pharmacologically isolated GABA(A) receptor-mediated IPSCs are decreased in the two partial nerve injury models compared with naive animals. An analysis of unitary IPSCs suggests that presynaptic GABA release is reduced after CCI and SNI. Partial nerve injury also decreases dorsal horn levels of the GABA synthesizing enzyme glutamic acid decarboxylase (GAD) 65 kDa ipsilateral to the injury and induces neuronal apoptosis, detected by terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling staining in identified neurons. Both of these mechanisms could reduce presynaptic GABA levels and promote a functional loss of GABAergic transmission in the superficial dorsal horn.
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Abstract
The ability to perform stepping and standing can be reacquired after complete thoracic spinal cord transection in adult cats with appropriate, repetitive training. We now compare GAD(67)A levels in the spinal cord of cats that were trained to step or stand. We confirmed that a complete spinal cord transection at approximately T12 increases glutamic acid decarboxylase (GAD)(67) in both the dorsal and ventral horns of L5-L7. We now show that step training decreases these levels toward control. Kinematic analyses show that this downward modulation is correlated inversely with stepping ability. Compared with intact cats, spinal cord-transected cats had increased punctate GAD(67) immunoreactivity around neurons in lamina IX at cord segments L5-L7. Compared with spinal nontrained cats, those trained to stand on both hindlimbs had more GAD(67) puncta bilaterally in a subset of lamina IX neurons. In cats trained to stand unilaterally, this elevated staining pattern was limited to the trained side and extended for at least 4 mm in the L6 and L7 segments. The location of this asymmetric GAD(67) staining corresponded to the motor columns of primary knee flexors, which are minimally active during standing, perhaps because of extensor-activated inhibitory interneuron projections. The responsiveness to only a few days of motor training, as well as the GABA-synthesizing potential in the spinal cord, persists for at least 25 months after the spinal cord injury. This modulation is specific to the motor task that is performed repetitively and is closely linked to the ability of the animal to perform a specific motor task.
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10
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Milbrandt JC, Holder TM, Wilson MC, Salvi RJ, Caspary DM. GAD levels and muscimol binding in rat inferior colliculus following acoustic trauma. Hear Res 2000; 147:251-60. [PMID: 10962189 DOI: 10.1016/s0378-5955(00)00135-0] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pharmacological studies of the inferior colliculus (IC) suggest that the inhibitory amino acid neurotransmitter gamma-aminobutyric acid (GABA) plays an important role in shaping responses to simple and complex acoustic stimuli. Several models of auditory dysfunction, including age-related hearing loss, tinnitus, and peripheral deafferentation, suggest an alteration of normal GABA neurotransmission in central auditory pathways. The present study attempts to further characterize noise-induced changes in GABA markers in the IC. Four groups (unexposed control, 0 h post-exposure, 42 h post-exposure, and 30 days post-exposure) of 3-month-old male Fischer 344 rats were exposed to a high intensity sound (12 kHz, 106 dB) for 10 h. Observed hair cell damage was primarily confined to the basal half of the cochlea. There was a significant decrease in glutamic acid decarboxylase (GAD(65)) immunoreactivity in the IC membrane fraction compared to controls (P<0.05) at 0 h (-41%) and 42 h (-28%) post-exposure, with complete recovery by 30 days post-exposure (P>0.98). Observed decreases in cytosolic levels of GAD(65) were not significant. Quantitative muscimol receptor binding revealed a significant increase (+20%) in IC 30 days after sound exposure (P<0.05). These data suggest that changes in GABA neurotransmission occur in the IC of animals exposed to intense sound. Additional studies are needed to determine whether these changes are a result of protective/compensatory mechanisms or merely peripheral differentiation, as well as whether these changes preserve or diminish central auditory system function.
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Affiliation(s)
- J C Milbrandt
- Southern Illinois University School of Medicine, Pharmacology Department, 801 N Rutledge St., P.O. Box 19629, Springfield, IL 62794-9629, USA
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Tillakaratne NJ, Mouria M, Ziv NB, Roy RR, Edgerton VR, Tobin AJ. Increased expression of glutamate decarboxylase (GAD(67)) in feline lumbar spinal cord after complete thoracic spinal cord transection. J Neurosci Res 2000; 60:219-30. [PMID: 10740227 DOI: 10.1002/(sici)1097-4547(20000415)60:2<219::aid-jnr11>3.0.co;2-f] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
To determine changes in gamma-aminobutyric acid (GABA) in the spinal cord in response to a complete transection, we examined the cellular and tissue changes of the two forms of GABA synthetic enzyme glutamate decarboxylase (GAD(65) and GAD(67)). In situ hybridization, immunohistochemistry, and Western blot analyses show that spinal cord transection between thoracic segments 12 and 13 results in an increase of GAD(67), but not GAD(65), protein and mRNA in the lumbar spinal cord. This increase occurs mainly in the dorsal horn and persists for at least 12 months. In addition, there was relatively high GAD(67)-immunoreactivity around the central canal, with dorsolateral GAD(67)-immunoreactive fibers extending toward the ependyma and into the central canal in the transected animals. We suggest that an increase in GAD(67) leads to increased GABA production in spinal neurons below the injury site, resulting in altered inhibition and trophic support during posttrauma recovery and adaptation. Increased GABA synthesis around the central canal, in the vicinity of ependymal cells, may represent part of a regenerative process in the mammalian spinal cord, reminiscent of that observed in lower vertebrates.
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Affiliation(s)
- N J Tillakaratne
- Department of Physiological Science, University of California, Los Angeles, USA
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Dumoulin A, Privat A, Giménez y Ribotta M. Transplantation of embryonic Raphe cells regulates the modifications of the gabaergic phenotype occurring in the injured spinal cord. Neuroscience 2000; 95:173-82. [PMID: 10619473 DOI: 10.1016/s0306-4522(99)00412-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Transection of the spinal cord yields a permanent deficit due to the interruption of descending and ascending tracts which subserve the supraspinal control of spinal cord functions. We have shown previously that transplantation below the level of the section of embryonic monoaminergic neurons can promote the recovery of some segmental functions via a local serotonergic and noradrenergic reinnervation. Moreover, the up-regulation of the corresponding receptors resulting from the section was corrected by the transplants. The aim of the present work was to determine whether such a graft could also influence non-monoaminergic local neurons, the GABAergic interneurons of the spinal cord. Following spinal cord transection, the number of cells which express glutamate decarboxylase (mol. wt 67,000) messenger RNA--a marker of GABA synthesis--increased significantly below the lesion compared with the intact animal. In contrast, in lesioned animals which had been grafted one week later with raphe neuroblasts, this number was close to control level. These post-grafting modifications were further associated with increased GABA immunoreactivity in the host tissue. These data suggest that the graft of embryonic raphe cells which compensates the deficit of serotonin in the distal segment also regulates the expression of the GABAergic phenotype in the host spinal cord. This regulation could be mediated by the re-establishment of a local functional innervation by both serotonin and GABAergic transplanted neurons and/or by trophic factors released from the embryonic cells. It appears then that grafted cells influence the host tissue in a complex manner, through the release and/or regulation of several neurotransmitter systems.
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Affiliation(s)
- A Dumoulin
- INSERM Unité 336, Université Montpellier II, France
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Abbott SD, Hughes LF, Bauer CA, Salvi R, Caspary DM. Detection of glutamate decarboxylase isoforms in rat inferior colliculus following acoustic exposure. Neuroscience 1999; 93:1375-81. [PMID: 10501462 DOI: 10.1016/s0306-4522(99)00300-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The inferior colliculus is a central auditory structure which serves as a site for the integration of ascending and descending auditory information. Changes in central auditory structures may occur with acoustic exposure, which cannot be explained by alterations in cochlear function alone. Rats were exposed to a 10-kHz tone at 100 dB SPL for 9 h. Auditory brainstem response measures showed an initial 25-30-dB threshold shift across all tested frequencies. By 30 days post-exposure, thresholds for clicks and most frequencies returned to near control levels; however, thresholds remained elevated at 10 and 20 kHz. Inner hair cell loss was confined to apical and basal ends of the cochlea, and did not exceed 20%. Inferior colliculus levels of the two isoforms of the GABA synthetic enzyme glutamate decarboxylase (65,000 and 67,000 mol. wt forms) were measured immediately post-exposure (0 h) and at two and 30 days post-exposure using quantitative immunocytochemical and western blotting techniques. Zero-hour measures revealed a significant increase in the level of glutamate decarboxylase (mol. wt 67,000) protein (118%), as well as in the optical density (35%) of immunolabeled cells. By 30 days post-exposure, inferior colliculus protein levels of both glutamate decarboxylase isoforms were significantly below unexposed controls (39% and 21% for the 65,000 and 67,000 mol. wt forms, respectively). These studies describe increased markers for GABA immediately following acoustic exposure, followed by a decline to below control levels from two to 30 days post-exposure. It remains to be determined whether noise trauma-induced changes in glutamate decarboxylase levels in the inferior colliculus reflect protective up-regulation in response to intense stimulation, followed by the establishment of new neurotransmitter equilibrium levels.
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Affiliation(s)
- S D Abbott
- Southern Illinois University School of Medicine, Pharmacology Department, Springfield, IL 62794-9629, USA
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Chaudieu I, Privat A. Neuroprotection of cultured foetal rat hippocampal cells against glucose deprivation: are GABAergic neurons less vulnerable or more sensitive to TCP protection? Eur J Neurosci 1999; 11:2413-21. [PMID: 10383631 DOI: 10.1046/j.1460-9568.1999.00658.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the rat brain, hippocampal neurons are particularly sensitive to secondary excitotoxic injury induced by ischaemia or hypoglycaemia. To determine some distinctive features of vulnerability among neuronal phenotypes in the hippocampus following a metabolic insult, we used an in vitro model of mild glucose deprivation. Primary cultures from the rat hippocampus (21 days in vitro) were deprived of glucose for 4 h and then were returned to the standard medium for 24 or 48 h. Survival of the GABAergic neuronal population was evaluated both by measuring [3H]GABA uptake and by counting GAD65-immunostained cells. This was compared with the survival of the total neuronal population evaluated by counting the neurofilament-200-immunostained cells. Glucose deprivation for 4 h followed by a recovery period of 48 h induced a decrease of 59% and 40% in the number of GAD65- and neurofilament-200-immunostained cells, respectively. Thus, GABAergic neurons were slightly more vulnerable to glucose deprivation than the other neurons in the hippocampal cell cultures. When the excitotoxic component of cellular death was blocked in the presence of TCP, an NMDA-antagonist, the survival of GABAergic neurons was almost complete after 48 h of recovery. In contrast, measurements of the release of lactate dehydrogenase in the medium indicated that TCP largely protected hippocampal cells after 24 h but was ineffective after 48 h. This observation was confirmed by immunostaining data which showed that after 48 h TCP did not significantly increase the survival of neurofilament-200-immunostained cells. These results indicate that after glucose deprivation and a recovery period of 48 h, GABAergic neurons in hippocampal cell cultures are not more resistant than other neurons but they are more sensitive to TCP protection.
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Affiliation(s)
- I Chaudieu
- Unité INSERM 336, ENSCM, 8 rue de lEcole Normale, 34296 Montpellier Cedex 5, France.
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15
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Abstract
The highly disagreeable sensation of pain results from an extraordinarily complex and interactive series of mechanisms integrated at all levels of the neuroaxis, from the periphery, via the dorsal horn to higher cerebral structures. Pain is usually elicited by the activation of specific nociceptors ('nociceptive pain'). However, it may also result from injury to sensory fibres, or from damage to the CNS itself ('neuropathic pain'). Although acute and subchronic, nociceptive pain fulfils a warning role, chronic and/or severe nociceptive and neuropathic pain is maladaptive. Recent years have seen a progressive unravelling of the neuroanatomical circuits and cellular mechanisms underlying the induction of pain. In addition to familiar inflammatory mediators, such as prostaglandins and bradykinin, potentially-important, pronociceptive roles have been proposed for a variety of 'exotic' species, including protons, ATP, cytokines, neurotrophins (growth factors) and nitric oxide. Further, both in the periphery and in the CNS, non-neuronal glial and immunecompetent cells have been shown to play a modulatory role in the response to inflammation and injury, and in processes modifying nociception. In the dorsal horn of the spinal cord, wherein the primary processing of nociceptive information occurs, N-methyl-D-aspartate receptors are activated by glutamate released from nocisponsive afferent fibres. Their activation plays a key role in the induction of neuronal sensitization, a process underlying prolonged painful states. In addition, upon peripheral nerve injury, a reduction of inhibitory interneurone tone in the dorsal horn exacerbates sensitized states and further enhance nociception. As concerns the transfer of nociceptive information to the brain, several pathways other than the classical spinothalamic tract are of importance: for example, the postsynaptic dorsal column pathway. In discussing the roles of supraspinal structures in pain sensation, differences between its 'discriminative-sensory' and 'affective-cognitive' dimensions should be emphasized. The purpose of the present article is to provide a global account of mechanisms involved in the induction of pain. Particular attention is focused on cellular aspects and on the consequences of peripheral nerve injury. In the first part of the review, neuronal pathways for the transmission of nociceptive information from peripheral nerve terminals to the dorsal horn, and therefrom to higher centres, are outlined. This neuronal framework is then exploited for a consideration of peripheral, spinal and supraspinal mechanisms involved in the induction of pain by stimulation of peripheral nociceptors, by peripheral nerve injury and by damage to the CNS itself. Finally, a hypothesis is forwarded that neurotrophins may play an important role in central, adaptive mechanisms modulating nociception. An improved understanding of the origins of pain should facilitate the development of novel strategies for its more effective treatment.
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Affiliation(s)
- M J Millan
- Institut de Recherches Servier, Psychopharmacology Department, Paris, France
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Zhang B, Levitt P, Murray M. Induction of presynaptic reexpression of an adhesion protein in lamina II after dorsal root deafferentation in adult rat spinal cord. Exp Neurol 1998; 149:468-72. [PMID: 9500956 DOI: 10.1006/exnr.1997.6722] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Limbic system-associated membrane protein (LAMP), a 64-kDa membrane protein, is an axon guidance adhesion molecule expressed by neurons in limbic system-related areas of the CNS. During development, LAMP is expressed on growing axons, growth cones, and their target neurons, but in adults it is restricted to membranes of somata and dendrites. In the adult spinal cord, LAMP immunoreactivity is found only on neurons of lamina II, lamina X, and the intermediolateral cell column and its ultrastructural localization is entirely postsynaptic. We studied changes in the expression of LAMP in lamina II of adult rat spinal cord after L1-S2 dorsal rhizotomy, a procedure that partially deafferents lamina II neurons and induces axonal sprouting by spared systems in lamina II. At the light microscopic level, LAMP immunoreactivity in lamina II was decreased in density at 3, 10, and 60 days postoperatively. This decrease in immunoreactivity suggests that LAMP expression by lamina II neurons may normally be regulated by specific afferent activity. Ultrastructurally, in control lamina II and after deafferentation in both control and deafferented lamina II at 3 and 60 days postoperatively, LAMP expression was restricted to postsynaptic membranes. Ten days after deafferentation, however, when axons are actively sprouting, LAMP was expressed on both axonal and postsynaptic membranes. The reexpression of LAMP on axonal profiles after deafferentation may identify axons that undergo sprouting in response to deafferentation.
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Affiliation(s)
- B Zhang
- Department of Neurobiology and Anatomy, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19129, USA
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