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Javadova A, Felmy F. GABA B receptor-mediated modulation in the developing dorsal nucleus of the lateral lemniscus. Eur J Neurosci 2024; 59:966-981. [PMID: 38180306 DOI: 10.1111/ejn.16246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 11/30/2023] [Accepted: 12/18/2023] [Indexed: 01/06/2024]
Abstract
The dorsal nucleus of the lateral lemniscus (DNLL) is a GABAergic, reciprocally connected auditory brainstem structure that continues to develop postnatally in rodents. One key feature of the DNLL is the generation of a strong, prolonged, ionotropic, GABAA receptor-mediated inhibition. Possible GABAB receptor-mediated signalling is unexplored in the DNLL. Here, we used Mongolian gerbils of either sex to describe GABAB receptor-mediated modulation of postsynaptic potassium currents and synaptic inputs in postnatal (P) animals of days 10/11 and 23-28. Throughout development, we observed the presence of a Baclofen-activated GABAB receptor-enhanced potassium outward conductance that is capable of suppressing action potential generation. In P10/11, old gerbils GABAB receptor activation enhances glutamatergic and suppresses ionotropic GABAergic synaptic transmission. During development, this differential modulation becomes less distinct, because in P22-28, old animals Baclofen-activated GABAB receptors rather enhance ionotropic GABAergic synaptic transmission, whereas glutamatergic transmission is both enhanced and suppressed. Blocking GABAB receptors causes an increase in ionotropic GABAergic transmission in P10/11 old gerbils that was independent on stimulation frequency but depended on the type of short-term plasticity. Together with the lack of Baclofen-induced changes in the synaptic paired-pulse ratio of either input type, we suggest that GABAB receptor-mediated modulation is predominantly postsynaptic and activates different signalling cascades. Thus, we argue that in DNLL neurons, the GABAB receptor is a post-synaptically located signalling hub that alters signalling cascades during development for distinct targets.
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Affiliation(s)
- Amina Javadova
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Hannover, Germany
- Infection Medicine and Veterinary Sciences (HGNI), Hannover Graduate School for Neurosciences, Hannover, Germany
| | - Felix Felmy
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Hannover, Germany
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2
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Ghenaatgar-Kasbi M, Rezaei M, Moharreri P, Heidarian Miri H, Sazegar G, Haghir H. The effect of maternal diabetes on the expression of gamma-aminobutyric acid and metabotropic glutamate receptors in male newborn rats' inferior colliculi. J Perinat Med 2023; 51:940-949. [PMID: 37139647 DOI: 10.1515/jpm-2022-0553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 02/28/2023] [Indexed: 05/05/2023]
Abstract
OBJECTIVES Few studies have examined the molecular alterations in the auditory pathway of infants of diabetic mothers, notwithstanding the fact that maternal diabetes may have an impact on the development of the neonatal peripheral and central nervous systems. Male newborn rats were studied to determine how maternal diabetes affected the expression of gamma-aminobutyric acid (GABAAα1 and GABAB1) and metabotropic glutamate (mGlu2) receptors in the inferior colliculus (IC) in this research. METHODS Female rats were given a single intraperitoneal injection of streptozotocin (STZ) at a 65 mg/kg dose to develop a model of diabetic mothers. The study population was split into sham, diabetes without treatment, and diabetes with insulin groups. Their male neonatal rats were anesthetized on P0, P7, and P14 after mating and delivery. The receptors' distribution pattern was studied using immunohistochemistry (IHC). RESULTS Pairwise comparison in the groups revealed that the GABA receptors (Aα1 and B1) were significantly downregulated in the diabetes without treatment group (p<0.001). Furthermore, pairwise comparison in the groups indicated significant mGlu2 upregulation in the diabetes without treatment group (p<0.001). Regarding the concentration of all receptors, there was no discernible distinction between the diabetes with insulin and sham groups. CONCLUSIONS This investigation showed that the concentration of GABAAα1 and GABAB1 receptors decreased significantly over time, whereas the concentration of mGlu2 receptors increased significantly over time in male neonatal rats born to streptozotocin-induced diabetic mothers.
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Affiliation(s)
- Maryam Ghenaatgar-Kasbi
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mohammad Rezaei
- Department of Physiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Payam Moharreri
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hamid Heidarian Miri
- Social Determinants of Health Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Ghasem Sazegar
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hossein Haghir
- Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
- Medical Genetic Research Center (MGRC), School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
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3
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Tureček R, Melichar A, Králíková M, Hrušková B. The role of GABA B receptors in the subcortical pathways of the mammalian auditory system. Front Endocrinol (Lausanne) 2023; 14:1195038. [PMID: 37635966 PMCID: PMC10456889 DOI: 10.3389/fendo.2023.1195038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
GABAB receptors are G-protein coupled receptors for the inhibitory neurotransmitter GABA. Functional GABAB receptors are formed as heteromers of GABAB1 and GABAB2 subunits, which further associate with various regulatory and signaling proteins to provide receptor complexes with distinct pharmacological and physiological properties. GABAB receptors are widely distributed in nervous tissue, where they are involved in a number of processes and in turn are subject to a number of regulatory mechanisms. In this review, we summarize current knowledge of the cellular distribution and function of the receptors in the inner ear and auditory pathway of the mammalian brainstem and midbrain. The findings suggest that in these regions, GABAB receptors are involved in processes essential for proper auditory function, such as cochlear amplifier modulation, regulation of spontaneous activity, binaural and temporal information processing, and predictive coding. Since impaired GABAergic inhibition has been found to be associated with various forms of hearing loss, GABAB dysfunction could also play a role in some pathologies of the auditory system.
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Affiliation(s)
- Rostislav Tureček
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Adolf Melichar
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Michaela Králíková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Bohdana Hrušková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
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4
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Pätz C, Console-Meyer L, Felmy F. Structural arrangement of auditory brainstem nuclei in the bats Phyllostomus discolor and Carollia perspicillata. J Comp Neurol 2022; 530:2762-2781. [PMID: 35703441 DOI: 10.1002/cne.25355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 04/24/2022] [Accepted: 05/14/2022] [Indexed: 11/10/2022]
Abstract
The structure of the mammalian auditory brainstem is evolutionarily highly plastic, and distinct nuclei arrange in a species-dependent manner. Such anatomical variability is present in the superior olivary complex (SOC) and the nuclei of the lateral lemniscus (LL). Due to the structure-function relationship in the auditory brainstem, the identification of individual nuclei supports the understanding of sound processing. Here, we comparatively describe the nucleus arrangement and the expression of functional markers in the auditory brainstem of the two bat species Phyllostomus discolor and Carollia perspicillata. Using immunofluorescent labeling, we describe the arrangement and identity of the SOC and LL nuclei based on the expression of synaptic markers (vesicular glutamate transporter 1 and glycine transporter 2), calcium-binding proteins, as well as the voltage-gated ion channel subunits Kv1.1 and HCN1. The distribution of excitatory and inhibitory synaptic labeling appears similar between both species and matches with that of other mammals. The detection of calcium-binding proteins indicates species-dependent differences and deviations from other mammals. Kv1.1 and HCN1 show largely the same expression pattern in both species, which diverges from other mammals, indicating functional adaptations in the cellular physiology of bat neurons.
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Affiliation(s)
- Christina Pätz
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Laura Console-Meyer
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Felix Felmy
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
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5
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The effect of inhibition on stimulus-specific adaptation in the inferior colliculus. Brain Struct Funct 2017; 223:1391-1407. [PMID: 29143124 DOI: 10.1007/s00429-017-1546-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 10/17/2017] [Indexed: 10/18/2022]
Abstract
The inferior colliculus is a center of convergence for inhibitory and excitatory synaptic inputs that may be activated simultaneously by sound stimulation. Stimulus repetition may generate response habituation by changing the efficacy of neuron's synaptic inputs. Specialized IC neurons reduce their response to repetitive tones, but restore their firing when a different and infrequent tone occurs, a phenomenon known as stimulus specific adaptation. Here, using the microiontophoresis technique, we determined the role of GABAA-, GABAB-, and glycinergic receptors in stimulus-specific adaptation (SSA). We found that blockade of postsynaptic GABAB receptors selectively modulated response adaptation to repetitive sounds, whereas blockade of presynaptic GABAB receptors exerted a gain control effect on neuron excitability. Adaptation decreased when postsynaptic GABAB receptors were blocked, but increased if the blockade affected the presynaptic GABAB receptors. A dual, paradoxical effect was elicited by blockade of glycinergic receptors, i.e., both increase and decrease in adaptation. Moreover, simultaneous co-application of GABAA, GABAB, and glycinergic antagonists demonstrated that local GABA- and glycine-mediated inhibition contributes to only about 50% of SSA. Therefore, inhibition via chemical synapses dynamically modulate the strength and dynamics of stimulus-specific adaptation, but does not generate it.
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Butt S, Ashraf F, Porter LA, Zhang H. Sodium salicylate reduces the level of GABAB receptors in the rat's inferior colliculus. Neuroscience 2015; 316:41-52. [PMID: 26705739 DOI: 10.1016/j.neuroscience.2015.12.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/08/2015] [Accepted: 12/11/2015] [Indexed: 10/22/2022]
Abstract
Previous studies have indicated that sodium salicylate (SS) can cause hearing abnormalities through affecting the central auditory system. In order to understand central effects of the drug, we examined how a single intraperitoneal injection of the drug changed the level of subunits of the type-B γ-aminobutyric acid receptor (GABAB receptor) in the rat's inferior colliculus (IC). Immunohistochemical and western blotting experiments were conducted three hours following a drug injection, as previous studies indicated that a tinnitus-like behavior could be reliably induced in rats within this time period. Results revealed that both subunits of the receptor, GABABR1 and GABABR2, reduced their level over the entire area of the IC. Such a reduction was observed in both cell body and neuropil regions. In contrast, no changes were observed in other brain structures such as the cerebellum. Thus, a coincidence existed between a structure-specific reduction in the level of GABAB receptor subunits in the IC and the presence of a tinnitus-like behavior. This coincidence likely suggests that a reduction in the level of GABAB receptor subunits was involved in the generation of a tinnitus-like behavior and/or used by the nervous system to restore normal hearing following application of SS.
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Affiliation(s)
- S Butt
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada
| | - F Ashraf
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada
| | - L A Porter
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada
| | - H Zhang
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada.
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Sodium salicylate potentiates the GABAB-GIRK pathway to suppress rebound depolarization in neurons of the rat's medial geniculate body. Hear Res 2015; 332:104-112. [PMID: 26688177 DOI: 10.1016/j.heares.2015.11.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 11/16/2015] [Accepted: 11/23/2015] [Indexed: 12/15/2022]
Abstract
Rebound depolarization (RD) is a voltage response to the offset from pre-hyperpolarization of neuronal membrane potential, which manifests a particular form of the postsynaptic membrane potential response to inhibitory presynaptic inputs. We previously demonstrated that sodium salicylate (NaSal), a tinnitus inducer, can drastically suppress the RD in neurons of rat medial geniculate body (MGB) (Su et al, 2012; PLoS ONE 7, e46969). The purpose of the present study was to investigate the underlying cellular mechanism by using whole-cell patch-clamp recordings in rat MGB slices. NaSal (1.4 mM) had no effects on the current mediated by T-type Ca(2+) channels, indicating that it does not target these channels to suppress the RD. Instead, NaSal was shown to hyperpolarize the resting membrane potential to suppress the RD. NaSal had no effects on the current mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, indicating that it does not target these channels to hyperpolarize the resting membrane potential. NaSal induced an outward leak current that could be abolished by CGP55845, a GABAB receptor blocker, or respectively by Ba(2+) and Tertiapin-Q, blockers for G-protein-gated inwardly rectifying potassium (GIRK) channels, indicating that NaSal potentiates the GABAB-GIRK pathway to hyperpolarize the resting membrane potential. Our study demonstrates that NaSal targets GABAB receptors to alter functional behaviors of MGB neurons, which may be implicated in NaSal-induced tinnitus.
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Stefanescu RA, Shore SE. NMDA Receptors Mediate Stimulus-Timing-Dependent Plasticity and Neural Synchrony in the Dorsal Cochlear Nucleus. Front Neural Circuits 2015; 9:75. [PMID: 26622224 PMCID: PMC4653590 DOI: 10.3389/fncir.2015.00075] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 10/30/2015] [Indexed: 12/19/2022] Open
Abstract
Auditory information relayed by auditory nerve fibers and somatosensory information relayed by granule cell parallel fibers converge on the fusiform cells (FCs) of the dorsal cochlear nucleus, the first brain station of the auditory pathway. In vitro, parallel fiber synapses on FCs exhibit spike-timing-dependent plasticity with Hebbian learning rules, partially mediated by the NMDA receptor (NMDAr). Well-timed bimodal auditory-somatosensory stimulation, in vivo equivalent of spike-timing-dependent plasticity, can induce stimulus-timing-dependent plasticity (StTDP) of the FCs spontaneous and tone-evoked firing rates. In healthy guinea pigs, the resulting distribution of StTDP learning rules across a FC neural population is dominated by a Hebbian profile while anti-Hebbian, suppressive and enhancing LRs are less frequent. In this study, we investigate in vivo, the NMDAr contribution to FC baseline activity and long term plasticity. We find that blocking the NMDAr decreases the synchronization of FC- spontaneous activity and mediates differential modulation of FC rate-level functions such that low, and high threshold units are more likely to increase, and decrease, respectively, their maximum amplitudes. Three significant alterations in mean learning-rule profiles were identified: transitions from an initial Hebbian profile towards (1) an anti-Hebbian; (2) a suppressive profile; and (3) transitions from an anti-Hebbian to a Hebbian profile. FC units preserving their learning rules showed instead, NMDAr-dependent plasticity to unimodal acoustic stimulation, with persistent depression of tone-evoked responses changing to persistent enhancement following the NMDAr antagonist. These results reveal a crucial role of the NMDAr in mediating FC baseline activity and long-term plasticity which have important implications for signal processing and auditory pathologies related to maladaptive plasticity of dorsal cochlear nucleus circuitry.
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Affiliation(s)
- Roxana A Stefanescu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan Ann Arbor, MI, USA
| | - Susan E Shore
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan Ann Arbor, MI, USA ; Department of Molecular and Integrative Physiology, University of Michigan Medical School Ann Arbor, MI, USA ; Department of Biomedical Engineering, University of Michigan Ann Arbor, MI, USA
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9
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Deviance detection in auditory subcortical structures: what can we learn from neurochemistry and neural connectivity? Cell Tissue Res 2015; 361:215-32. [DOI: 10.1007/s00441-015-2134-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 01/22/2015] [Indexed: 12/18/2022]
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10
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Patel CR, Zhang H. Local Application of Sodium Salicylate Enhances Auditory Responses in the Rat's Dorsal Cortex of the Inferior Colliculus. Front Neurol 2014; 5:235. [PMID: 25452744 PMCID: PMC4231951 DOI: 10.3389/fneur.2014.00235] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 10/30/2014] [Indexed: 11/19/2022] Open
Abstract
Sodium salicylate (SS) is a widely used medication with side effects on hearing. In order to understand these side effects, we recorded sound-driven local-field potentials in a neural structure, the dorsal cortex of the inferior colliculus (ICd). Using a microiontophoretic technique, we applied SS at sites of recording and studied how auditory responses were affected by the drug. Furthermore, we studied how the responses were affected by combined local application of SS and an agonists/antagonist of the type-A or type-B γ-aminobutyric acid receptor (GABAA or GABAB receptor). Results revealed that SS applied alone enhanced auditory responses in the ICd, indicating that the drug had local targets in the structure. Simultaneous application of the drug and a GABAergic receptor antagonist synergistically enhanced amplitudes of responses. The synergistic interaction between SS and a GABAA receptor antagonist had a relatively early start in reference to the onset of acoustic stimulation and the duration of this interaction was independent of sound intensity. The interaction between SS and a GABAB receptor antagonist had a relatively late start, and the duration of this interaction was dependent on sound intensity. Simultaneous application of the drug and a GABAergic receptor agonist produced an effect different from the sum of effects produced by the two drugs released individually. These differences between simultaneous and individual drug applications suggest that SS modified GABAergic inhibition in the ICd. Our results indicate that SS can affect sound-driven activity in the ICd by modulating local GABAergic inhibition.
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Affiliation(s)
- Chirag R Patel
- Department of Biological Sciences, University of Windsor , Windsor, ON , Canada
| | - Huiming Zhang
- Department of Biological Sciences, University of Windsor , Windsor, ON , Canada
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11
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Oyanagi M, Kaneko K, Kaneko Y, Sasaki M, Nishida C, Matsuda Y, Mitsui T. Proteomic analysis of Nipponia nippon (ID#162). Anim Sci J 2014; 85:814-32. [PMID: 24961376 DOI: 10.1111/asj.12214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Accepted: 01/28/2014] [Indexed: 11/28/2022]
Abstract
We investigated the proteome of a female Crested Ibis (Nipponia nippon, ID#162) that died on March 10, 2010 at the Sado Japanese Crested Ibis Conservation Center. Protein preparations from the brain, trachea, liver, heart, lung, proventriculus, muscular stomach, small intestine, duodenum, ovary and neck muscle were subjected to in-solution shotgun mass spectrometry (MS)/MS analyses using an LTQ Orbitrap XL mass spectrometer. A search of the National Center for Biotechnology Information Gallus gallus databases revealed 4253 GI (GenInfo Identifier) numbers with the sum of the same 11 tissues examined in the Crested Ibis. To interpret the obtained proteomics data, it was verified in detail with the data obtained from the brain of the Crested Ibis. It has been reported that drebrin A is specifically expressed in adult chicken brain. In the shotgun proteomic analyses of the Crested Ibis, we identified drebrin A as a brain-specific protein. Furthermore, Western blotting analysis of the protein preparations from 10 tissues of the Crested Ibis and 150-day-old hens using anti-drebrin antibodies showed intensive expression of approximately 110 kDa polypeptides of drebrin in both brains. We believe firmly that the present data will contribute to initial and fundamental steps toward understanding the Crested Ibis proteome.
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Affiliation(s)
- Mitsuru Oyanagi
- Genome Research Center, Faculty of Agriculture, Niigata University, Niigata, Japan; Graduate School of Science and Technology, Niigata University, Niigata, Japan; Center for Toki and Ecological Restoration, Niigata University, Niigata, Japan
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12
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Zheng Y, McPherson K, Smith PF. Effects of early and late treatment with L-baclofen on the development and maintenance of tinnitus caused by acoustic trauma in rats. Neuroscience 2013; 258:410-21. [PMID: 24291770 DOI: 10.1016/j.neuroscience.2013.11.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 11/01/2013] [Accepted: 11/18/2013] [Indexed: 10/26/2022]
Abstract
Subjective tinnitus is a chronic neurological disorder in which phantom sounds are perceived. Recent evidence supports the hypothesis that tinnitus is related to neuronal hyperactivity in auditory brain regions, and consequently drugs that increase GABAergic neurotransmission in the CNS, such as the GABA(B) receptor agonist L-baclofen, may be effective as a treatment. The aim of this study was to investigate the effects of early (5 mg/kg s.c., 30 min and then every 24 h for 5 days following noise exposure) and late treatment (3 mg/kg/day s.c. for 4.5 weeks starting at 17.5 weeks following noise exposure) with l-baclofen on the psychophysical attributes of tinnitus in a conditioned lick suppression model following acoustic trauma in rats. Acoustic trauma (a 16-kHz, 115-dB pure tone presented unilaterally for 1h) resulted in a significant decrease in the suppression ratio (SR) compared to sham controls in response to 20-kHz tones at 2, 10 and 17.5 weeks post-exposure (P ≤ 0.009, P ≤ 0.02 and P ≤ 0.03, respectively). However, l-baclofen failed to prevent the development of tinnitus when administered during the first 5 days following the acoustic trauma and also failed to reverse it when treatment was carried out every day for 4.5 weeks. We also found that treatment with L-baclofen did not alter the expression of the GABA(B)-R2 subunit in the cochlear nucleus of noise-exposed animals.
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Affiliation(s)
- Y Zheng
- Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago Medical School, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - K McPherson
- Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago Medical School, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - P F Smith
- Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago Medical School, University of Otago, Dunedin, New Zealand; Brain Health Research Centre, University of Otago, Dunedin, New Zealand.
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13
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Fan GR, Yin ZD, Sun Y, Chen S, Zhang WJ, Huang X, Kong WJ, Zhang HL. Reversible neurotoxicity of kanamycin on dorsal cochlear nucleus. Brain Res 2013; 1502:30-46. [PMID: 23333799 DOI: 10.1016/j.brainres.2012.12.049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 10/13/2012] [Accepted: 12/27/2012] [Indexed: 01/05/2023]
Abstract
The time course of aminoglycoside neurotoxic effect on cochlear nucleus is still obscure. We examined dynamic pathological changes of dorsal cochlear nucleus (DCN) and investigated whether apoptosis or autophagy was upregulated in the neurotoxic course of kanamycin on DCN after kanamycin treatment. Rats were treated with kanamycin sulfate/kg/day at a dose of 500mg by subcutaneous injection for 10 days. Dynamic pathological changes, neuron density and neuron apoptosis of the DCN were examined at 1, 7, 14, 28, 56, 70 and 140 days after kanamycin treatment. The expressions of JNK1, DAPK2, Bcl-2, p-Bcl-2, Caspase-3, LC3B and Beclin-1 were also detected. Under transmission electron microscopy, the mitochondrial swelling and focal vacuoles as well as endoplasmic reticulum dilation were progressively aggravated from 1 day to 14 days, and gradually recovered from 28 days to 140 days. Meanwhile, both autophagosomes and autolysosomes were increased from 1 day to 56 days. Only few neurons were positive to the TUNEL staining. Moreover, neither the expressions of caspase-3 and DAPK2 nor neurons density of DCN changed significantly. LC3-II was drastically increased at 7 days. Beclin-1 was upgraded at 1 and 7 days. P-Bcl-2 increased at 1, 7, 14 and 28 days. JNK1 increased at 7 days, and Bcl-2 was downgraded at 140 days. LC3-B positive neurons were increased at 1, 7 and 14 days. These data demonstrated that the neurons damage of the DCN caused by kanamycin was reversible and autophagy was upregulated in the neurotoxic course of kanamycin on DCN through JNK1-mediated phosphorylation of Bcl-2 pathway.
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Affiliation(s)
- Guo-Run Fan
- Department of Otorhinolaryngology, Union Hospital of Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1277, Wuhan 430022, PR China
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14
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Jamal L, Khan AN, Butt S, Patel CR, Zhang H. The level and distribution of the GABA(B)R1 and GABA(B)R2 receptor subunits in the rat's inferior colliculus. Front Neural Circuits 2012. [PMID: 23189044 PMCID: PMC3506002 DOI: 10.3389/fncir.2012.00092] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The type B γ-aminobutyric acid receptor (GABA(B) receptor) is an important neurotransmitter receptor in the midbrain auditory structure, the inferior colliculus (IC). A functional GABA(B) receptor is a heterodimer consisting of two subunits, GABA(B)R1 and GABA(B)R2. Western blotting and immunohistochemical experiments were conducted to examine the expression of the two subunits over the IC including its central nucleus, dorsal cortex, and external cortex (ICc, ICd, and ICx). Results revealed that the two subunits existed in both cell bodies and the neuropil throughout the IC. The two subunits had similar regional distributions over the IC. The combined level of cell body and neuropil labeling was higher in the ICd than the other two subdivisions. Labeling in the ICc and ICx was stronger in the dorsal than the ventral regions. In spite of regional differences, no defined boundaries were formed between different areas. For both subunits, the regional distribution of immunoreactivity in the neuropil was parallel to that of combined immunoreactivity in the neuropil and cell bodies. The density of labeled cell bodies tended to be higher but sizes of cell bodies tended to be smaller in the ICd than in the other subdivisions. No systematic regional changes were found in the level of cell body immunoreactivity, except that GABA(B)R2-immunoreactive cell bodies in the ICd had slightly higher optic density (OD) than in other regions. Elongated cell bodies existed throughout the IC. Many labeled cell bodies along the outline of the IC were oriented in parallel to the outline. No strong tendency of orientation was found in labeled cell bodies in ICc. Regional distributions of the subunits in ICc correlated well with inputs to this subdivision. Our finding regarding the contrast in the level of neuropil immunoreactivity among different subdivisions is consistent with the fact that the GABA(B) receptor has different pre- and postsynaptic functions in different IC regions.
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Affiliation(s)
- Lena Jamal
- Department of Biological Sciences, University of Windsor Windsor, ON, Canada
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Patel CR, Redhead C, Cervi AL, Zhang H. Neural sensitivity to novel sounds in the rat's dorsal cortex of the inferior colliculus as revealed by evoked local field potentials. Hear Res 2012; 286:41-54. [PMID: 22406035 DOI: 10.1016/j.heares.2012.02.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2010] [Revised: 12/20/2011] [Accepted: 02/07/2012] [Indexed: 10/28/2022]
Abstract
Evoked local field potentials in response to contralaterally presented tone bursts were recorded from the rat's dorsal cortex of the inferior colliculus (ICd). An oddball stimulus paradigm was used to study the sensitivity of ensembles of neurons in the ICd to novel sounds. Our recordings indicate that neuron ensembles in the ICd display stimulus-specific adaptation when a large contrast in both frequency and probability of occurrence exists between the two tone bursts used for generating an oddball paradigm. A local field potential evoked by a tone burst presented as a deviant stimulus has a larger amplitude than that evoked by the same sound presented as a standard stimulus. The difference between the two responses occurs after the initial rising phases of their predominant deflections. The degree of stimulus-specific adaptation increases with the rate of sound presentation up to 8/s, the highest rate used in this study. A comparison between our results and those from previous studies suggests that differences exist between responses to oddball paradigms in the ICd and those in the primary auditory cortex, a major source of projection to the ICd. These differences suggest that local mechanisms exist in the ICd for suppressing neural responses to frequently presented sounds and enhancing responses to rarely presented sounds. Thus, the ICd may serve as an important component of an integrative circuit in the brain for detecting novel sounds in the acoustic environment.
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Affiliation(s)
- Chirag R Patel
- Department of Biological Sciences, 401 Sunset Ave., University of Windsor, Windsor, Ontario, Canada N9B 3P4
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