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Murase S, Sakitani N, Maekawa T, Yoshino D, Takano K, Konno A, Hirai H, Saito T, Tanaka S, Shinohara K, Kishi T, Yoshikawa Y, Sakai T, Ayaori M, Inanami H, Tomiyasu K, Takashima A, Ogata T, Tsuchimochi H, Sato S, Saito S, Yoshino K, Matsuura Y, Funamoto K, Ochi H, Shinohara M, Nagao M, Sawada Y. Interstitial-fluid shear stresses induced by vertically oscillating head motion lower blood pressure in hypertensive rats and humans. Nat Biomed Eng 2023; 7:1350-1373. [PMID: 37414976 PMCID: PMC10651490 DOI: 10.1038/s41551-023-01061-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 05/27/2023] [Indexed: 07/08/2023]
Abstract
The mechanisms by which physical exercise benefits brain functions are not fully understood. Here, we show that vertically oscillating head motions mimicking mechanical accelerations experienced during fast walking, light jogging or treadmill running at a moderate velocity reduce the blood pressure of rats and human adults with hypertension. In hypertensive rats, shear stresses of less than 1 Pa resulting from interstitial-fluid flow induced by such passive head motions reduced the expression of the angiotensin II type-1 receptor in astrocytes in the rostral ventrolateral medulla, and the resulting antihypertensive effects were abrogated by hydrogel introduction that inhibited interstitial-fluid movement in the medulla. Our findings suggest that oscillatory mechanical interventions could be used to elicit antihypertensive effects.
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Affiliation(s)
- Shuhei Murase
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
- Department of Orthopaedic Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Naoyoshi Sakitani
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
- Department of Cell Biology, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Takahiro Maekawa
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Daisuke Yoshino
- Division of Advanced Applied Physics, Institute of Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
| | - Kouji Takano
- Department of Rehabilitation for Brain Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Ayumu Konno
- Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Hirokazu Hirai
- Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Taku Saito
- Department of Orthopaedic Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Sakae Tanaka
- Department of Orthopaedic Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Keisuke Shinohara
- Department of Cardiovascular Medicine, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Takuya Kishi
- Department of Cardiology, Graduate School of Medicine, International University of Health and Welfare, Okawa, Japan
| | - Yuki Yoshikawa
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Takamasa Sakai
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | | | - Hirohiko Inanami
- Inanami Spine & Joint Hospital/Iwai Orthopaedic Medical Hospital, Iwai Medical Foundation, Tokyo, Japan
| | - Koji Tomiyasu
- Center of Sports Science and Health Promotion, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Atsushi Takashima
- Department of Assistive Technology, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Toru Ogata
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
- Department of Rehabilitation Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hirotsugu Tsuchimochi
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Shinya Sato
- Department of Advanced Medical Technologies, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Shigeyoshi Saito
- Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita, Japan
| | - Kohzoh Yoshino
- School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Japan
| | - Yuiko Matsuura
- Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan
| | | | - Hiroki Ochi
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Masahiro Shinohara
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Motoshi Nagao
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
| | - Yasuhiro Sawada
- Department of Rehabilitation for Motor Functions, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan.
- Department of Orthopaedic Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
- Department of Cell Biology, National Cerebral and Cardiovascular Center, Suita, Japan.
- Division of Advanced Applied Physics, Institute of Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan.
- Department of Clinical Research, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan.
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Dos Santos RR, Bernardino TC, da Silva MCM, de Oliveira ACP, Drumond LE, Rosa DV, Massensini AR, Moraes MFD, Doretto MC, Romano-Silva MA, Reis HJ. Neurochemical abnormalities in the hippocampus of male rats displaying audiogenic seizures, a genetic model of epilepsy. Neurosci Lett 2021; 761:136123. [PMID: 34293418 DOI: 10.1016/j.neulet.2021.136123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 07/11/2021] [Accepted: 07/16/2021] [Indexed: 11/17/2022]
Abstract
BACKGROUND Epilepsy is a disorder characterized by recurrent seizures that affects 1% of the population. However, the neurochemical alterations observed in epilepsy are not fully understood. There are different animal models of epilepsy, such as genetic or drug induced. In the present study, we utilize Wistar Audiogenic Rats (WAR), a murine strain that develops seizures in response to high intensity audio stimulation, in order to investigate abnormalities in glutamatergic and GABAergic systems. METHODS Synaptosomes and glial plasmalemmal vesicles were prepared from hippocampus and cortex, respectively. Glutamate and GABA release and uptake were assayed by monitoring the fluorescence and using L-[3H]-radiolabeled compounds. Glutamate and calcium concentration in the synaptosomes were also measured. The expression of neuronal calcium sensor 1 (NCS-1) was determined by western blot. RESULTS Glutamate and GABA release evoked by KCl was decreased in WAR compared to control Wistar rats. Calcium independent release was not considerably different in both groups. The total amount of glutamate of synaptosomes, as well as glutamate uptake by synaptosomes and GPV were also decreased in WAR in comparison with the controls. In addition, [Ca2+]i of hippocampal synaptosomes, as well as NCS-1 expression in the hippocampus, were increased in WAR in comparison with controls. CONCLUSION In conclusion, our results suggest that WAR have important alterations in the glutamatergic and GABAergic pathways, as well as an increased expression of NCS-1 in the hippocampus and inferior colliculus. These alterations may be linked to the spreading of hyperexcitability and recruitment of various brain regions.
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Affiliation(s)
- Rodrigo Ribeiro Dos Santos
- Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais. Av Alfredo Balena 190, CEP 30130-100 Belo Horizonte, MG, Brazil; Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Túlio C Bernardino
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Maria Carolina Machado da Silva
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Antônio C P de Oliveira
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Luciana E Drumond
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Daniela V Rosa
- Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais. Av Alfredo Balena 190, CEP 30130-100 Belo Horizonte, MG, Brazil
| | - André R Massensini
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Márcio F D Moraes
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Maria C Doretto
- Núcleo de Neurociências, Departamento de Biofísica e Fisiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil
| | - Marco A Romano-Silva
- Departamento de Saúde Mental, Faculdade de Medicina, Universidade Federal de Minas Gerais. Av Alfredo Balena 190, CEP 30130-100 Belo Horizonte, MG, Brazil
| | - Helton J Reis
- Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901 Belo Horizonte, MG, Brazil.
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Smith KM, Zalewski NL, Budhram A, Britton JW, So E, Cascino GD, Ritaccio AL, McKeon A, Pittock SJ, Dubey D. Musicogenic epilepsy: Expanding the spectrum of glutamic acid decarboxylase 65 neurological autoimmunity. Epilepsia 2021; 62:e76-e81. [PMID: 33764529 DOI: 10.1111/epi.16888] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 03/05/2021] [Accepted: 03/10/2021] [Indexed: 01/01/2023]
Abstract
The objective of this study was to describe serological association of musicogenic epilepsy and to evaluate clinical features and outcomes of seropositive cases. Through retrospective chart review, musicogenic epilepsy patients were identified. Among 16 musicogenic epilepsy patients, nine underwent autoantibody evaluations and all had high-titer glutamic acid decarboxylase 65-immunoglobulin G (GAD65-IgG; >20 nmol·L-1 , serum, normal ≤ .02 nmol·L-1 , eight women). Median GAD65-IgG serum titer was 294 nmol·L-1 (20.3-3005 nmol·L-1 ), and median cerebrospinal fluid titer (n = 4) was 14.7 nmol·L-1 . All patients had temporal lobe epilepsy, and bitemporal epileptiform abnormalities were common. Right temporal lobe seizures were most frequently captured when seizures were induced by music on electroencephalogram (3/4; 75%). Intravenous (IV) methylprednisolone and/or IV Ig (IVIG) was utilized in four patients, with one having greater than 50% reduction. Rituximab (n = 2) and mycophenolate (n = 1) were ineffective. Two patients underwent right temporal lobe resections but continued to have seizures. Vagus nerve stimulation was effective at reducing seizures in one patient by 50%, and an additional patient was seizure-free by avoiding provoking music. Right temporal lobe epilepsy was more common among patients with musicogenic epilepsy when compared to nonmusicogenic GAD65 epilepsies (n = 71, 89% vs. 47%, p = .03). GAD65-IgG should be tested in patients with musicogenic epilepsy, given implications for management and screening for comorbid autoimmune conditions.
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Affiliation(s)
- Kelsey M Smith
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Adrian Budhram
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Clinical Neurological Sciences, London Health Sciences Centre, Western University, London, Ontario, Canada
| | | | - Elson So
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | | | - Andrew McKeon
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Sean J Pittock
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Divyanshu Dubey
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
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Umeoka EH, Eiras MC, Viana IG, Giorgi VS, Bueno A, Damasceno DC, Garcia-Cairasco N, Navarro PA. Maternal reproductive performance and fetal development of the Wistar Audiogenic Rat (WAR) strain. Syst Biol Reprod Med 2018; 65:87-94. [PMID: 29927665 DOI: 10.1080/19396368.2018.1483443] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Wistar Audiogenic Rat (WAR) strain is an animal model for epilepsy studies, the chronic multifactorial disease that affects millions of people worldwide. The animals of this strain are genetically predisposed to sound-induced seizures, called audiogenic seizures, and have been used for many years in studies to understand the mechanisms involved in the epilepsies and their neuropsychiatric comorbidities, as well as the screening of potential anti-convulsant agents. Nevertheless, little is known about the reproductive characteristics of these animals. The main goal of this study was to characterize the female reproductive performance and the fetal growth of WARs in comparison to the Wistar rats, obtaining important information for physiology and behavioral studies, as well as for the preservation of the strain. The results indicated few differences between WAR and Wistar regarding the female reproductive performance. There was no significant difference in the number of pregnant females by mating, number of live births per female, number of cells per blastocyst, and several characteristics related to reproductive performance, such as pre- and post-implantation losses. However, significant differences were observed in birth weight and weight gain until weaning, with WAR animals presenting a body weight below Wistar at birth and reduced body weight gain during the lactation period. In addition, the WAR females showed lower body weight on the day 20 of pregnancy and a larger number of corpora lutea, when compared with those of Wistar animals. Thus, we conclude that although Wistar and WAR strains have few differences in their reproductive performance, which might impact future physiological life challenges or others experimentally induced procedures, it still is a very viable strain regarding reproduction. Abbreviations: CONCEA: National Council for the Control of Animal Experimentation; GEPR: genetically epilepsy-prone rats; WAR: Wistar Audiogenic Rat.
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Affiliation(s)
- Eduardo H Umeoka
- a Department of Gynecology and Obstetrics , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil.,b Neuroscience and Behavioral Sciences Department , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil.,c Department of Physiology , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil
| | - Matheus C Eiras
- d Department of Genetics , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil
| | - Iara G Viana
- a Department of Gynecology and Obstetrics , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil
| | - Vanessa S Giorgi
- a Department of Gynecology and Obstetrics , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil
| | - Aline Bueno
- e Gynecology, Obstetrics and Mastology Postgraduate Course , Botucatu Medical School, Univ. Estadual Paulista-UNESP , Botucatu, São Paulo , Brazil
| | - Débora C Damasceno
- e Gynecology, Obstetrics and Mastology Postgraduate Course , Botucatu Medical School, Univ. Estadual Paulista-UNESP , Botucatu, São Paulo , Brazil
| | - Norberto Garcia-Cairasco
- b Neuroscience and Behavioral Sciences Department , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil.,c Department of Physiology , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil
| | - Paula A Navarro
- a Department of Gynecology and Obstetrics , Ribeirão Preto School of Medicine, University of São Paulo , Ribeirão Preto, São Paulo , Brazil
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Coleman JR, Thompson KC, Wilson MA, Wilson SP. Audiogenic seizure activity following HSV-1 GAD65 sense or antisense injection into inferior colliculus of Long-Evans rat. Epilepsy Behav 2017; 71:238-242. [PMID: 27993512 DOI: 10.1016/j.yebeh.2016.08.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 08/22/2016] [Accepted: 08/25/2016] [Indexed: 11/19/2022]
Abstract
Herpes virus technology involving manipulation of GAD65 was used to study effects on audiogenic seizures (AGS). Audiogenic seizure behaviors were examined following injections of replication-defective herpes simplex virus (HSV-1) vectors incorporating sense or antisense toward GAD65 along with 10% lac-Z into the central nucleus of inferior colliculus (CNIC) of Long-Evans rats. In seizure-sensitive animals developmentally primed by intense sound exposure, injection of GAD65 in the sense orientation increased wild running latencies and reduced incidence of clonus compared with lac-Z only, unoperated, and vehicle seizure groups. In contrast, infection of CNIC with GAD65 antisense virus resulted in 100% incidence of wild running and clonus behaviors in AGS animals. Unprimed animals not operated continued to show uniform absence of seizure activity. Administration of GAD65 antisense virus into CNIC produced novel wild running and clonus behaviors in some unprimed animals. Staining for β-galactosidase in all vector animals revealed no differences in pattern or numbers of immunoreactive cells at injection sites. Qualitatively, typical small and medium multipolar/stellate and medium fusiform neurons appeared in the CNIC of vector animals. These results demonstrate that HSV-1 vector constructs implanted into the CNIC can predictably influence incidence and severity of AGS and suggest that viral vectors can be useful in studying GABA mechanisms with potential for therapeutic application in epilepsy. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".
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Affiliation(s)
- James R Coleman
- Department of Psychology, University of South Carolina, Barnwell College, Columbia, SC 20208, United States; Department of Pharmacology, Physiology & Neuroscience, University of South Carolina, School of Medicine, Columbia, SC 29209, United States; Psychology Program, South University, 9 Science Ct., Columbia, SC 29203, United States.
| | - Karen C Thompson
- Department of Psychology, University of South Carolina, Barnwell College, Columbia, SC 20208, United States; Behavioral Studies Program, Columbia College, Columbia, SC 29203, United States
| | - Marlene A Wilson
- Department of Pharmacology, Physiology & Neuroscience, University of South Carolina, School of Medicine, Columbia, SC 29209, United States
| | - Steven P Wilson
- Department of Pharmacology, Physiology & Neuroscience, University of South Carolina, School of Medicine, Columbia, SC 29209, United States
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6
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Muñoz LJ, Carballosa-Gautam MM, Yanowsky K, García-Atarés N, López DE. The genetic audiogenic seizure hamster from Salamanca: The GASH:Sal. Epilepsy Behav 2017; 71:181-192. [PMID: 27072920 DOI: 10.1016/j.yebeh.2016.03.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 03/01/2016] [Accepted: 03/04/2016] [Indexed: 12/17/2022]
Abstract
The hamster has been previously described as a paroxysmal dystonia model, but our strain is currently recognized as a model of audiogenic seizures (AGS). The original first epileptic hamster appeared spontaneously at the University of Valladolid, where it was known as the GPG:Vall line, and was transferred to the University of Salamanca where a new strain was developed, named GASH:Sal. By testing auditory brainstem responses, the GASH:Sal exhibits elevated auditory thresholds that indicate a hearing impairment. Moreover, amplified fragment length polymorphism analysis distinguished genetic differences between the susceptible GASH:Sal hamster strain and the control Syrian hamsters. The GASH:Sal constitutes an experimental model of reflex epilepsy of audiogenic origin derived from an autosomal recessive disorder. Thus, the GASH:Sal exhibits generalized tonic-clonic seizures, characterized by a short latency period after auditory stimulation, followed by wild running, a convulsive phase, and finally stupor, with origin in the brainstem. The seizure profile of the GASH:Sal is similar to those exhibited by other models of inherited AGS susceptibility, which decreases after six months of age, but the proneness across generations is maintained. The GASH:Sal can be considered a reliable model of audiogenic seizures, suitable to investigate current antiepileptic pharmaceutical treatments as well as novel therapeutic drugs. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".
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Affiliation(s)
- Luis J Muñoz
- Animal Research Service, University of Salamanca, 37007 Salamanca, Spain.
| | - Melissa M Carballosa-Gautam
- Institute for Neuroscience of Castilla y León/IBSAL, C/ Pintor Fernando Gallego, No. 1, 37007 Salamanca, Spain; The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, 1095 NW 14thTerrace, Room 2-34, Miami, FL 33136, USA
| | - Kira Yanowsky
- Institute for Neuroscience of Castilla y León/IBSAL, C/ Pintor Fernando Gallego, No. 1, 37007 Salamanca, Spain
| | - Natividad García-Atarés
- Department of Anatomy and Radiology, School of Medicine, University of Valladolid, 47007, Spain
| | - Dolores E López
- Institute for Neuroscience of Castilla y León/IBSAL, C/ Pintor Fernando Gallego, No. 1, 37007 Salamanca, Spain; Department of Cell Biology and Pathology, University of Salamanca, Spain
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7
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Bandara SB, Eubig PA, Sadowski RN, Schantz SL. Developmental PCB Exposure Increases Audiogenic Seizures and Decreases Glutamic Acid Decarboxylase in the Inferior Colliculus. Toxicol Sci 2015; 149:335-45. [PMID: 26543103 DOI: 10.1093/toxsci/kfv237] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Previously, we observed that developmental polychlorinated biphenyl (PCB) exposure resulted in an increase in audiogenic seizures (AGSs) in rats. However, the rats were exposed to loud noise in adulthood, and were not tested for AGS until after 1 year of age, either of which could have interacted with early PCB exposure to increase AGS susceptibility. This study assessed susceptibility to AGS in young adult rats following developmental PCB exposure alone (without loud noise exposure) and investigated whether there was a decrease in GABA inhibitory neurotransmission in the inferior colliculus (IC) that could potentially explain this effect. Female Long-Evans rats were dosed orally with 0 or 6 mg/kg/day of an environmentally relevant PCB mixture from 28 days prior to breeding until the pups were weaned at postnatal day 21. One male-female pair from each litter was retained for the AGS study whilst another was retained for Western blot analysis of glutamic acid decarboxylase (GAD) and GABAAα1 receptor in the IC, the site in the auditory midbrain where AGS are initiated. There was a significant increase in the number and severity of AGSs in the PCB groups, with females somewhat more affected than males. GAD65 was decreased but there was no change in GAD67 or GABAAα1 in the IC indicating decreased inhibitory regulation in the PCB group. These results confirm that developmental PCB exposure alone is sufficient to increase susceptibility to AGS, and provide the first evidence for a possible mechanism of action at the level of the IC.
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Affiliation(s)
| | - Paul A Eubig
- *Neuroscience Program and Department of Comparative Biosciences, University of Illinois, Urbana-Champaign, Urbana, Illinois 61802; and
| | - Renee N Sadowski
- *Neuroscience Program and Beckman Institute, University of Illinois, Urbana-Champaign, Urbana, Illinois 60801
| | - Susan L Schantz
- *Neuroscience Program and Department of Comparative Biosciences, University of Illinois, Urbana-Champaign, Urbana, Illinois 61802; and Beckman Institute, University of Illinois, Urbana-Champaign, Urbana, Illinois 60801
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8
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Brown JW, Moeller A, Schmidt M, Turner SC, Nimmrich V, Ma J, Rueter LE, van der Kam E, Zhang M. Anticonvulsant effects of structurally diverse GABA(B) positive allosteric modulators in the DBA/2J audiogenic seizure test: Comparison to baclofen and utility as a pharmacodynamic screening model. Neuropharmacology 2015; 101:358-69. [PMID: 26471422 DOI: 10.1016/j.neuropharm.2015.10.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/31/2015] [Accepted: 10/04/2015] [Indexed: 02/02/2023]
Abstract
The GABA(B) receptor has been indicated as a promising target for multiple CNS-related disorders. Baclofen, a prototypical orthosteric agonist, is used clinically for the treatment of spastic movement disorders, but is associated with unwanted side-effects, such as sedation and motor impairment. Positive allosteric modulators (PAM), which bind to a topographically-distinct site apart from the orthosteric binding pocket, may provide an improved side-effect profile while maintaining baclofen-like efficacy. GABA, the major inhibitory neurotransmitter in the CNS, plays an important role in the etiology and treatment of seizure disorders. Baclofen is known to produce anticonvulsant effects in the DBA/2J mouse audiogenic seizure test (AGS), suggesting it may be a suitable assay for assessing pharmacodynamic effects. Little is known about the effects of GABA(B) PAMs, however. The studies presented here sought to investigate the AGS test as a pharmacodynamic (PD) screening model for GABA(B) PAMs by comparing the profile of structurally diverse PAMs to baclofen. GS39783, rac-BHFF, CMPPE, A-1295120 (N-(3-(4-(4-chloro-3-fluorobenzyl)-6-methoxy-3,5-dioxo-4,5-dihydro-1,2,4-triazin-2(3H)-yl)phenyl)acetamide), and A-1474713 (N-(3-(4-(4-chlorobenzyl)-3,5-dioxo-4,5-dihydro-1,2,4-triazin-2(3H)-yl)phenyl)acetamide) all produced robust, dose-dependent anticonvulsant effects; a similar profile was observed with baclofen. Pre-treatment with the GABA(B) antagonist SCH50911 completely blocked the anticonvulsant effects of baclofen and CMPPE in the AGS test, indicating such effects are likely mediated by the GABA(B) receptor. In addition to the standard anticonvulsant endpoint of the AGS test, video tracking software was employed to assess potential drug-induced motor side-effects during the acclimation period of the test. This analysis was sensitive to detecting drug-induced changes in total distance traveled, which was used to establish a therapeutic index (TI = hypoactivity/anticonvulsant effects). Calculated TIs for A-1295120, CMPPE, rac-BHFF, GS39783, and A-1474713 were 5.31x, 5.00x, 4.74x, 3.41x, and 1.83x, respectively, whereas baclofen was <1. The results presented here suggest the DBA/2J mouse AGS test is a potentially useful screening model for detecting PD effects of GABA(B) PAMs and can provide an initial read-out on target-related motor side-effects. Furthermore, an improved TI was observed for PAMs compared to baclofen, indicating the PAM approach may be a viable therapeutic alternative to baclofen.
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Affiliation(s)
- Jordan W Brown
- Neuroscience Discovery, AbbVie, Inc., 1 North Waukegan Rd., North Chicago, IL 60064, United States.
| | - Achim Moeller
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Martin Schmidt
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Sean C Turner
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Volker Nimmrich
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Junli Ma
- Drug Metabolism and Pharmacokinetics, AbbVie, Inc., North Chicago, IL 60064, United States
| | - Lynne E Rueter
- Neuroscience Discovery, AbbVie, Inc., 1 North Waukegan Rd., North Chicago, IL 60064, United States
| | - Elizabeth van der Kam
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co KG, Knollstrasse, Ludwigshafen 67061, Germany
| | - Min Zhang
- Neuroscience Discovery, AbbVie, Inc., 1 North Waukegan Rd., North Chicago, IL 60064, United States
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9
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Abstract
Voltage-gated K(+) channels (Kv) represent the largest family of genes in the K(+) channel family. The Kv1 subfamily plays an essential role in the initiation and shaping of action potentials, influencing action potential firing patterns and controlling neuronal excitability. Overlapping patterns with differential expression and precise localization of Kv1.1 and Kv1.2 channels targeted to specialized subcellular compartments contribute to distinctive patterns of neuronal excitability. Dynamic regulation of the components in these subcellular domains help to finely tune the cellular and regional networks. Disruption of the expression, distribution, and density of these channels through deletion or mutation of the genes encoding these channels, Kcna1 and Kcna2, is associated with neurologic pathologies including epilepsy and ataxia in humans and in rodent models. Kv1.1 and Kv1.2 knockout mice both have seizures beginning early in development; however, each express a different seizure type (pathway), although the channels are from the same subfamily and are abundantly coexpressed. Voltage-gated ion channels clustered in specific locations may present a novel therapeutic target for influencing excitability in neurologic disorders associated with some channelopathies.
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Affiliation(s)
- Carol A Robbins
- Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Seattle, WA 98195, USA
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10
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Pacey LKK, Heximer SP, Hampson DR. Increased GABAB Receptor-Mediated Signaling Reduces the Susceptibility of Fragile X Knockout Mice to Audiogenic Seizures. Mol Pharmacol 2009; 76:18-24. [DOI: 10.1124/mol.109.056127] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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11
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Zhvaniya MG, Bolkvadze TN, Dzhaparidze ND, Kotariya NT, Chkhikvishvili T. Effect of acoustic stimulation on cell composition of auditory brain structures in Krushinskii-Molodkina rats. Bull Exp Biol Med 2007; 142:419-21. [PMID: 17415426 DOI: 10.1007/s10517-006-0381-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We studied the effect of acoustic stimulation on cell composition of auditory brain structures in Krushinskii-Molodkina rats. Significant structural changes in the inferior colliculi of rats with high seizure activity were revealed 1 month after acoustic stimulation. Therefore, this brain structure plays a role in the development of audiogenic epileptic activity.
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Affiliation(s)
- M G Zhvaniya
- Laboratory of Brain Structure and Development, Institute of Physiology, Georgian Academy of Sciences, Tbilisi
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12
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Evans MS, Cady CJ, Disney KE, Yang L, Laguardia JJ. Three brief epileptic seizures reduce inhibitory synaptic currents, GABA(A) currents, and GABA(A)-receptor subunits. Epilepsia 2006; 47:1655-64. [PMID: 17054688 DOI: 10.1111/j.1528-1167.2006.00634.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Cellular mechanisms activated during seizures may exacerbate epilepsy. gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in brain, and we hypothesized that brief epileptic seizures may reduce GABA function. METHODS We used audiogenic seizures (AGSs) in genetically epilepsy-prone rats (GEPRs) to investigate effects of seizures on GABA-mediated inhibition in the presence of epilepsy. GEPRs are uniformly susceptible to AGSs beginning at 21 postnatal days. AGSs are brief convulsions lasting approximately 20 s, and they begin in inferior colliculus (IC). We evoked three seizures in GEPRs and compared the results with those in seizure-naive GEPRs and nonepileptic Sprague-Dawley (SD) rats, the GEPR parent strain. RESULTS Whole-cell recording in IC slices showed that GABA-mediated monosynaptic inhibitory postsynaptic currents (IPSCs) were reduced 55% by three brief epileptic seizures. Whole-cell recording in IC neuronal cultures showed that currents elicited by GABA were reduced 67% by three seizures. Western blotting for the alpha1 and alpha4 subunits of the GABA(A) receptor showed no statistically significant effects. In contrast, three brief epileptic seizures reduced gamma2 subunit levels by 80%. CONCLUSIONS The effects of the very first seizures, in animals known to be epileptic, in an area of brain known to be critical to the seizure network, were studied. The results indicate that even brief epileptic seizures can markedly reduce IPSCs and GABA currents and alter GABA(A)-receptor subunit protein levels. The cause of the reductions in IPSCs and GABA currents is likely to be altered receptor subunit composition, with reduced gamma2 levels causing reduced GABA(A)-receptor sensitivity to GABA. Seizure-induced reductions in GABA-mediated inhibition could exacerbate epilepsy.
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Affiliation(s)
- M Steven Evans
- Department of Neurology, Southern Illinois University School of Medicine, Springfield, IL 62794-9637, USA.
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13
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14
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Vinogradova LV, Kuznetsova GD, Shatskova AB, van Rijn CM. Vigabatrin in Low Doses Selectively Suppresses the Clonic Component of Audiogenically Kindled Seizures in Rats. Epilepsia 2005; 46:800-10. [PMID: 15946321 DOI: 10.1111/j.1528-1167.2005.52604.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE The effect of systemic administration of the gamma-aminobutyric acid (GABA)-transaminase inhibitor vigabatrin (VGB) on different components of convulsions was tested in the model of audiogenically kindled seizures, which consist of brainstem (running, tonus) and forebrain (clonus) elements. METHODS Audiogenically susceptible rats of Krushinsky-Molodkina (KM), Wistar, and WAG/Rij strains received repeated sound stimulation (60 dB, 10-80 kHz) until kindled audiogenic seizures were reliably elicited. Kindled audiogenic seizures consisted of running, tonic, and generalized clonic phases in KM rats (severe audiogenic seizures) and of running and Racine stage 5 facial/forelimb clonus in Wistar and WAG/Rij rats (moderate seizures). Vehicle, 100, or 200 mg/kg of VGB was intraperitoneally injected 2, 4 and 24 h before the induction of kindled audiogenic seizures. RESULTS At both doses, VGB did not change the seizure latency and the duration of running and tonic convulsions, but suppressed clonic ones in all rat strains. In KM rats, the mean duration of posttonic clonus was significantly reduced at 24 h after 100 mg/kg and from 4 h after 200 mg/kg. In Wistar and WAG/Rij rats, the mean duration of facial/forelimb clonus was reduced from 4 and 2 h after 100- and 200-mg/kg administration, respectively; 24 h after the high-dose injection, clonus was completely blocked in all rats of both strains. No difference in efficacy of VGB between Wistar and WAG/Rij rats was observed. CONCLUSIONS VGB more effectively suppresses clonic convulsions than running and tonic ones in audiogenically kindled rats. It is supposed that this selective anticonvulsive effect of VGB results from different sensitivities of forebrain and brainstem epileptic networks to the presumed GABA enhancement.
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MESH Headings
- Acoustic Stimulation
- Animals
- Anticonvulsants/administration & dosage
- Anticonvulsants/pharmacology
- Anticonvulsants/therapeutic use
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Epilepsy, Reflex/diagnosis
- Epilepsy, Reflex/prevention & control
- Female
- Injections, Intraperitoneal
- Kindling, Neurologic/drug effects
- Kindling, Neurologic/physiology
- Male
- Motor Activity/drug effects
- Motor Activity/physiology
- Rats
- Rats, Inbred Strains
- Rats, Wistar
- Seizures/prevention & control
- Severity of Illness Index
- Species Specificity
- Vigabatrin/administration & dosage
- Vigabatrin/pharmacology
- Vigabatrin/therapeutic use
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Affiliation(s)
- Ludmilla V Vinogradova
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia
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15
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Silva RCB, Sandner G, Brandão ML. Unilateral electrical stimulation of the inferior colliculus of rats modifies the prepulse modulation of the startle response (PPI): effects of ketamine and diazepam. Behav Brain Res 2005; 160:323-30. [PMID: 15863228 DOI: 10.1016/j.bbr.2004.12.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 12/16/2004] [Accepted: 12/20/2004] [Indexed: 10/25/2022]
Abstract
The magnitude of an acoustic startle response can be reduced by a weak stimulus presented immediately before the startle-eliciting noise. This phenomenon has been termed prepulse inhibition of the startle reaction (PPI). Previous studies indicated that the primary neural pathways mediating PPI belong to the brain stem and that the inferior colliculus (IC) was crucial. Its destruction reduced PPI. Stimulations applied to brain areas may be as deleterious as lesions. Therefore, we looked for the possibility of a brain stimulation applied to the IC during a PPI test to reduce also PPI. Rats were implanted with chronic electrodes, their tips being aimed at the IC. They were located within or close to the inter-colliculus nucleus. A train of stimulations was applied and PPI was tested alternately during and between periods of stimulation. As the most common method used to attenuate PPI consists in administrating drugs, for example ketamine, we also tested the effect of this drug. Another drug was also tested, diazepam, since it alters the functioning of the IC without any known effect on PPI. This allowed a comparative analysis of the neurobiological and the pharmacological effects. It appeared that the stimulation decreased PPI quantitatively as much as ketamine (6 mg/kg) without an effect of the basic startle reaction. These effects did not interfere with each other. Diazepam (1 mg/kg) did not modify PPI, neither under stimulation nor per se. Only for a very high dose (4 mg/kg), a sedative and myo-relaxant one the basic startle and PPI were altered.
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Affiliation(s)
- R C B Silva
- I.N.S.E.R.M., U666, Institut de Physiologie, Faculté de médecine, Université Louis Pasteur, Strasbourg, France
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16
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Bagri A, Sandner G, Di Scala G. Aversive effects elicited by electrical stimulation of the inferior colliculus in normal and audiogenic seizure susceptible rats. Neurosci Lett 2005; 379:180-4. [PMID: 15843059 DOI: 10.1016/j.neulet.2004.12.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Revised: 12/13/2004] [Accepted: 12/23/2004] [Indexed: 11/25/2022]
Abstract
Trains of electrical stimulations were applied to the dorsal or ventral part of the inferior colliculus (IC) of audiogenic seizure susceptible rats from the AGSR strain. Threshold and duration of wild running (WR), were evaluated in the first experiment. All stimulation sites elicited WR, even in normal control rats. Stimulation of the IC of AGSR rats required a lower quantity of current, i.e., such brain sites were more sensitive to the current, than normal controls. The duration of post-stimulus WR was shorter in AGSR rats. Lower quantities of current applied to the ventral IC were needed to elicit WR than to the dorsal IC in AGSR rats. In a second experiment, using the same stimulations sites in the same rats, the emotional effect of the stimulation was tested through an instrumental learning procedure (switch-off paradigm) in which the rat was trained to press a bar to put an end to the stimulation. Both dorsal and ventral IC stimulation sites sustained switch-off behavior in AGSR rats, but only ventral IC stimulation sites sustained switch-off learning in control rats.
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Affiliation(s)
- Abdallah Bagri
- Laboratoire de Physiologie et Pharmacologie, Faculté des Sciences et Techniques, BP: 577, Settat 26000, Morocco.
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17
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Ishimoto T, Chiba S, Omori N. Convulsive seizures induced by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid microinjection into the mesencephalic reticular formation in rats. Brain Res 2004; 1021:69-75. [PMID: 15328033 DOI: 10.1016/j.brainres.2004.03.081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/01/2004] [Indexed: 11/22/2022]
Abstract
Effects of microinjections of a single 2 or 10 nmol dose of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) into the unilateral mesencephalic reticular formation (MRF) on behavior and on the electroencephalogram were examined in rats (n=30) over a 15-min period (Exp. 1); subsequent effects of sound stimulation with key jingling applied at 15, 30, and 45 min after the injection were observed (Exp. 2). The microinjections of a 2 nmol dose of AMPA (n=15) induced hyperactivity (15 of 15 rats) and running/circling (10 of 15 rats) in Exp. 1, and hyperactivity (5 of 15 rats) in Exp. 2. Moreover, the microinjections of a 10 nmol dose of AMPA (n=15) induced hyperactivity (15 of 15 rats), running/circling (13 of 15 rats), generalized tonic-clonic seizures (GTCS) (4 of 15 rats), and amygdala kindling-like seizures (AMKS) (8 of 15 rats) in Exp. 1; electroencephalographic seizure discharges were predominantly observed in the MRF during hyperactivity, running/circling and GTCS, while those predominantly observed in the amygdala were during AMKS. In Exp. 2, hyperactivity (15 of 15 rats), running/circling (14 of 15 rats) and GTCS (6 of 15 rats) were elicited by sound stimulation, although AMKS were not. The control group of rats (n=15) which received a single dose of saline microinjection into the unilateral MRF showed no behavioral or electroencephalographic changes in both Exp. 1 and 2. These findings suggest that potentiation of excitatory amino acid neurotransmission induced by AMPA injection into the MRF plays an important role not only in the development of hyperactivity, running/circling, GTCS and AMKS, but also in the development of audiogenic seizures.
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Affiliation(s)
- Takahiro Ishimoto
- Department of Psychiatry and Neurology, Asahikawa Medical College, Midorigaoka higashi 2-1-1-1, Asahikawa 078-8510, Japan
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18
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Abstract
Many treatments for the epilepsies and affective disorder share the properties of seizure suppression and mood stabilization. Moreover, affective disorders and the epilepsies appear to share partially similar pathogenic mechanisms. A component of the shared predisposition appears to arise from noradrenergic and serotonergic deficits. Increasing evidence supports the hypothesis that noradrenergic and/or serotonergic elevation is a mechanism of therapeutic benefit shared by most antidepressants and many antiepileptic medications. Medication induced alterations in GABAergic, glutamatergic, and CRH (corticotropin releasing hormone) containing neurons may also contribute to the shared therapeutic properties of antidepressant and antiepileptic medications.
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Affiliation(s)
- Phillip C Jobe
- Department of Biomedical and Therapeutic Sciences, University of Illinois College of Medicine, PO Box 1649, Peoria, Illinois 61656-1649, USA.
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19
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de Paula HMG, Hoshino K. Antipanic procedures reduce the strychnine-facilitated wild running of rats. Behav Brain Res 2003; 147:157-62. [PMID: 14659581 DOI: 10.1016/s0166-4328(03)00147-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Wild running (WR) behavior of rats seen in response to intense acoustic stimulation of audiogenic seizure-paradigm is very similar to the panic flight and can be facilitated by subconvulsive doses of strychnine. The present work aimed to test whether antipanic procedures, such as dorsal periaqueductal gray (dPAG) lesion and imipramine treatments, affect the strychnine-facilitated WR. In study 1, six Wistar male adult rats with electrolytic lesion of dPAG had their WR completely blocked, whereas it was facilitated in 50% of sham-lesioned control rats by a dose of 0.5 mg/kg of strychnine administered intraperitoneal. This effect was not reproduced with a higher strychnine dose (1.0 mg/kg). In study 2, the effects of imipramine were investigated by testing 36 rats under a dose of strychnine that induces WR in 50% of subjects. They were assigned into three experimental groups: imipramine treatments of 5.0 and 10.0 mg/kg, and infusions of saline. All these treatments were subchronical with three intraperitoneal injections within 24 h. Imipramine (10.0 mg/kg) reduced the incidence of WR in comparison to the saline results. It is concluded that strychnine-facilitated WR is reduced by antipanic procedures and, therefore, can be viewed as a manifestation closely related to panic.
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Affiliation(s)
- H M G de Paula
- Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Campus de Boutcatu, SP, Brazil.
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20
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Simeone TA, Donevan SD, Rho JM. Molecular biology and ontogeny of gamma-aminobutyric acid (GABA) receptors in the mammalian central nervous system. J Child Neurol 2003; 18:39-48; discussion 49. [PMID: 12661937 DOI: 10.1177/08830738030180012101] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
gamma-Aminobutyric acid (GABA) is the predominant inhibitory neurotransmitter in the mammalian central nervous system. After release from nerve terminals, GABA binds to at least two classes of postsynaptic receptors (ie, GABAA and GABAB), which are nearly ubiquitous in the brain. GABAA receptors are postsynaptic heteropentameric complexes that display unique physiologic and pharmacologic properties based on subunit composition. Activation of GABAA receptors in mature neurons results in membrane hyperpolarization, which is mediated principally by inward chloride flux, whereas in early stages of brain development, GABAA receptor activation causes depolarization of the postsynaptic membrane. GABA, receptors reside both presynaptically and postsynaptically, exist as heterodimers and are coupled to voltage-dependent ion channels through interactions with heterotrimeric G proteins. This review summarizes the molecular biology and ontogeny of GABAA and GABAB receptors, highlighting some of their putative roles during normal brain development as well as in disease states such as epilepsy.
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Affiliation(s)
- Timothy A Simeone
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT, USA
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21
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Ross KC, Waldman BC, Conejero-Goldberg C, Freed W, Coleman JR. Transplantation of M213-2O cells with enhanced GAD67 expression into the inferior colliculus alters audiogenic seizures. Exp Neurol 2002; 177:338-40. [PMID: 12429237 DOI: 10.1006/exnr.2002.7987] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of the present study was to examine the effects of GABA-producing cell transplants on audiogenic seizures (AGS). The M213-2O cell line was derived from fetal rat striatum and has GABAergic properties. This cell line was further modified to express human GAD(67) and produce elevated levels of GABA. The present study compares the effects of parent M213-2O cell transplants with those of GAD(67)-modified M213-2O cells in AGS-prone Long-Evans rats. Two weeks following implantation of engineered cells, latency to AGS-typical wild running was increased compared to nonimplanted subjects. Survival of the transplanted cells was confirmed by immunochemical labeling of GAD(67) and Epstein-Barr virus nuclear antigen. These findings support the use of GABA-producing cell lines to modify seizure activity.
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Affiliation(s)
- Karen C Ross
- Department of Psychology, University of South Carolina, Columbia, South Carolina 29208, USA
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22
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Winer JA, Chernock ML, Larue DT, Cheung SW. Descending projections to the inferior colliculus from the posterior thalamus and the auditory cortex in rat, cat, and monkey. Hear Res 2002; 168:181-95. [PMID: 12117520 DOI: 10.1016/s0378-5955(02)00489-6] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Projections from the posterior thalamus and medial geniculate body were labeled retrogradely with wheat germ agglutinin conjugated to horseradish peroxidase injected into the rat, cat, and squirrel monkey inferior colliculus. Neurons were found ipsilaterally in the (1) medial division of the medial geniculate body, (2) central gray, (3) posterior limitans nucleus, and the (4) reticular part of the substantia nigra. Bilateral projections involved the (5) peripeduncular/suprapeduncular nucleus, (6) subparafascicular and posterior intralaminar nuclei, (7) nucleus of the brachium of the inferior colliculus, (8) lateral tegmental/lateral mesencephalic areas, and (9) deep layers of the superior colliculus. The medial geniculate projection was concentrated in the caudal one-third of the thalamus; in contrast, the labeling in the subparafascicular nucleus, substantia nigra, and central gray continued much further rostrally. Robust anterograde labeling corresponded to known patterns of tectothalamic projection. Biotinylated dextran amine deposits in the rat inferior colliculus revealed that (1) many thalamotectal cells were elongated multipolar neurons with long, sparsely branched dendrites, resembling neurons in the posterior intralaminar system, and that other labeled cells were more typical of thalamic relay neurons; (2) some cells have reciprocal projections. Similar results were seen in the cat and squirrel monkey. The widespread origins of descending thalamic influences on the inferior colliculus may represent a phylogenetically ancient feedback system onto the acoustic tectum, one that predates the corticocollicular system and modulates nonauditory centers and brainstem autonomic nuclei. Besides their role in normal hearing such pathways may influence behaviors ranging from the startle reflex to the genesis of sound-induced seizures.
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Affiliation(s)
- Jeffery A Winer
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720-3200, USA. .edu
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23
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Abstract
gamma-Aminobutyric acid (GABA), acting at GABA(A) receptors, mediates inhibition in inferior colliculus (IC) central nucleus (ICc) neurons and plays a prominent role in mediating acoustically evoked non-monotonicity, offset inhibition, and binaural inhibition, and is also important in tonic inhibition. The IC plays an important role in a number of pathophysiological conditions that involve hearing, including tinnitus, age-related hearing loss, and audiogenic seizures (AGS). AGS are a major form of rodent neurological disorder that can be genetically mediated and can also be readily induced in both young and mature animals. A deficit in GABA-mediated inhibition in IC neurons has been shown to be a critical mechanism in genetic and induced forms of AGS. Thus, both endogenously evoked GABA-mediated inhibition and exogenously applied GABA are reduced in efficacy in IC neurons of rats that are susceptible to AGS. GABA-mediated inhibition in IC neurons is significantly more easily blocked by a GABA(A) antagonist in genetic and induced forms of AGS in vivo and in vitro. AGS can be induced in normal animals by treatments that reduce the effectiveness of GABA in the IC. Glutamate-mediated excitation is a critical element of neurotransmission in IC neurons, and excessive activation of glutamate receptors in the IC is also strongly implicated as the other major mechanism in the pathophysiology of AGS. These neurotransmitter abnormalities result in excessive firing of ICc neurons that acts as the critical initiation mechanism for triggering seizures in response to intense acoustic stimuli.
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Affiliation(s)
- Carl L Faingold
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA.
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Sakamoto T, Niki H. Acoustic priming lowers the threshold for electrically induced seizures in mice inferior colliculus, but not in the deep layers of superior colliculus. Brain Res 2001; 898:358-63. [PMID: 11306023 DOI: 10.1016/s0006-8993(01)02163-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Mice become highly susceptible to audiogenic seizures (AGS) after exposing them to an intense noise in their early life (priming). To elucidate the brain mechanisms for this priming effect of AGS, we compared the threshold current intensities inducing AGS syndromes between primed (n=88) and non-primed (n=84) mice by electrically stimulating the central nucleus and external cortex of the inferior colliculus (CIC and ECIC), and the deep layers of the superior colliculus (DLSC). The threshold for wild running was significantly lower for the primed mice than for the control mice in the case of the CIC and ECIC, but not the DLSC. The current intensity for inducing clonic seizure was lower for the primed mice than for the control mice in the case of the ECIC. These results show that the inferior colliculus (IC) plays an important role in the priming effect of AGS in mice, but that the DLSC does not.
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Affiliation(s)
- T Sakamoto
- Laboratory for Neurobiology of Emotion, Brain Science Institute (BSI), RIKEN, 2-1 Hirosawa, Wako-City, 351-0198, Saitama, Japan.
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Ishimoto T, Omori N, Mutoh F, Chiba S. Convulsive seizures induced by N-methyl-D-aspartate microinjection into the mesencephalic reticular formation in rats. Brain Res 2000; 881:152-8. [PMID: 11036153 DOI: 10.1016/s0006-8993(00)02830-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Effects of microinjections of a single 2 or 10 nmol dose of N-methyl-D-aspartate (NMDA) into the unilateral mesencephalic reticular formation (MRF) on behavior and electroencephalogram were examined in rats (n=18) during a 15 min period (Exp. 1), and subsequent effects of sound stimulation with key jingling applied at 15, 30, and 45 min after the injections were observed (Exp. 2). The microinjections of 2 nmol dose of NMDA (n=10) induced hyperactivity (9 of 10 rats) and running/circling (8 of 10 rats) in Exp. 1, and hyperactivity (3 of 10 rats) in Exp. 2. Moreover, the microinjections of 10 nmol dose of NMDA (n=8) induced not only hyperactivity (8 of 8 rats) and running/circling (7 of 8 rats) but also generalized tonic-clonic seizures (GTCS) (5 of 8 rats) in Exp. 1; these seizure patterns were also elicited by sound stimulation in Exp. 2. The seizure patterns were accompanied by electroencephalographic seizure discharges in the MRF and the motor cortex. In contrast, the control group rats (n=10) which received a single dose of saline microinjection into the unilateral MRF showed no behavioral or electroencephalographic changes in both Exp. 1 and 2. These findings suggest that the MRF has an important role in the development of GTCS, which follows hyperactivity and running/circling, and that potentiation of excitatory neurotransmission in the MRF participates in the development of audiogenic seizures as well as GTCS.
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Affiliation(s)
- T Ishimoto
- Department of Psychiatry and Neurology, Asahikawa Medical College, Midorigaoka higashi 2-1-1-1, 078-8510, Asahikawa, Japan.
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26
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Bauer CA, Brozoski TJ, Holder TM, Caspary DM. Effects of chronic salicylate on GABAergic activity in rat inferior colliculus. Hear Res 2000; 147:175-82. [PMID: 10962183 DOI: 10.1016/s0378-5955(00)00130-1] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It is well accepted that salicylate ototoxicity results in reversible tinnitus in humans. Salicylate-induced tinnitus may be an example of plasticity of the central auditory system and could potentially serve as a model to further understand mechanisms of tinnitus generation. This study examined levels of glutamic acid decarboxylase (GAD) and the binding characteristics of the GABA(A) receptor in auditory brainstem structures of Long-Evans rats chronically treated with salicylate. Western blotting revealed a significant 63% (P<0.008) elevation of GAD levels in the inferior colliculus (IC) of salicylate-treated subjects. This occurred in subjects demonstrating behavioral evidence of tinnitus. Muscimol saturation analysis was indicative of a salicylate-related increase in receptor affinity. Linear regression of [(3)H]muscimol saturation analysis data revealed a significant (P<0.05) reduction in K(d) values in whole IC (-48%), as well as in the central nucleus of IC (CIC, -58%) and combined external and dorsal cortex of IC (E/DCIC, -46%). The number of GABA(A) binding sites (B(max)) were also significantly (P<0.05) decreased. These changes were observed only in central auditory structures. This suggests that GAD expression and GABA(A) receptor binding characteristics may be altered with chronic exposure to sodium salicylate and these changes may represent aberrant plasticity clinically experienced as tinnitus.
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Affiliation(s)
- C A Bauer
- Southern Illinois University School of Medicine, Springfield, IL 62794-9662, USA.
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Ross KC, Coleman JR. Developmental and genetic audiogenic seizure models: behavior and biological substrates. Neurosci Biobehav Rev 2000; 24:639-53. [PMID: 10940439 DOI: 10.1016/s0149-7634(00)00029-4] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Audiogenic seizure (AGS) models of developmental or genetic origin manifest characteristic indices of generalized seizures such as clonus or tonus in rodents. Studies of seizure-resistant strains in which AGS is induced by intense sound exposure during postnatal development provide models in which other neural abnormalities are not introduced along with AGS susceptibility. A critical feature of all AGS models is the reduction of neural activity in the auditory pathways from deafness during development. The initiation and propagation of AGS activity relies upon hyperexcitability in the auditory system, particularly the inferior colliculus (IC) where bilateral lesions abolish AGS. GABAergic and glutaminergic mechanisms play crucial roles in AGS, as in temporal lobe models of epilepsy, and participate in AGS modulatory and efferent systems including the superior colliculus, substantia nigra, basal ganglia and structures of the reticular formation. Catecholamine and indolamine systems also influence AGS severity. AGS models are useful for elucidating the underlying mechanisms for formation and expression of generalized epileptic behaviors, and evaluating the efficacy of modern treatment strategies such as anticonvulsant medication and neural grafting.
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Affiliation(s)
- K C Ross
- Department of Psychology, University of South Carolina, Columbia, SC 29208, USA
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Evans MS, Li Y, Faingold C. Inferior Colliculus Intracellular Response Abnormalities In Vitro Associated With Susceptibility to Ethanol Withdrawal Seizures. Alcohol Clin Exp Res 2000. [DOI: 10.1111/j.1530-0277.2000.tb02081.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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29
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Feng HJ, Faingold CL. Modulation of audiogenic seizures by histamine and adenosine receptors in the inferior colliculus. Exp Neurol 2000; 163:264-70. [PMID: 10785466 DOI: 10.1006/exnr.2000.7382] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Susceptibility to behaviorally similar audiogenic seizures (AGS) occurs genetically and is inducible during ethanol withdrawal (ETX). Comparisons between AGS mechanisms of genetically epilepsy-prone rats (GEPR-9s) and ethanol-withdrawn rats (ETX-Rs) are yielding information about general pathophysiological mechanisms of epileptogenesis. The inferior colliculus (IC) is the AGS initiation site. Excitatory amino acid (EAA) abnormalities in the IC are implicated in AGS, and histamine and adenosine receptor activation each reduce EAA release and inhibit several seizure types. Previous studies indicate that focal infusion of an adenosine receptor agonist into the IC blocked AGS in GEPR-9s, but the effects of adenosine receptor activation in the IC on AGS in ETX-Rs are unknown. The effects of histamine receptor activation on either form of AGS are also unexamined. The present study evaluated effects of histamine or a nonselective adenosine A(1) agonist, 2-chloroadenosine, on AGS by focal microinjection into the IC. Ethanol dependence and AGS susceptibility were induced in normal rats by intragastric ethanol. Histamine (40 or 60 nmol/side) significantly reduced AGS in GEPR-9s, but histamine in doses up to 120 nmol/side did not affect AGS in ETX-Rs. 2-Chloroadenosine (5 or 10 nmol/side) did not affect AGS in ETX-Rs, despite the effectiveness of lower doses of this agent in GEPR-9s reported previously. Thus, histamine and adenosine receptors in the IC modulate AGS of GEPR-9s, but do not modulate ETX-induced AGS. The reasons for this difference may involve the chronicity of AGS susceptibility in GEPR-9s, which may lead to more extensive neuromodulation as compensatory mechanisms to limit the seizures compared to the acute AGS of ETX-Rs.
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Affiliation(s)
- H J Feng
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois 62794-9629, USA
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30
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Fu M, Nikolic D, Van Breemen RB, Silverman RB. Mechanism of Inactivation of γ-Aminobutyric Acid Aminotransferase by (S)-4-Amino-4,5-dihydro-2-thiophenecarboxylic Acid. J Am Chem Soc 1999. [DOI: 10.1021/ja9915551] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mengmeng Fu
- Contribution from the Department of Chemistry and Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3113 and the Department of Medicinal Chemistry, University of Illinois at Chicago, Chicago, Illinois 60612-7231
| | - Dejan Nikolic
- Contribution from the Department of Chemistry and Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3113 and the Department of Medicinal Chemistry, University of Illinois at Chicago, Chicago, Illinois 60612-7231
| | - Richard B. Van Breemen
- Contribution from the Department of Chemistry and Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3113 and the Department of Medicinal Chemistry, University of Illinois at Chicago, Chicago, Illinois 60612-7231
| | - Richard B. Silverman
- Contribution from the Department of Chemistry and Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3113 and the Department of Medicinal Chemistry, University of Illinois at Chicago, Chicago, Illinois 60612-7231
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31
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Fu M, Silverman RB. Isolation and characterization of the product of inactivation of gamma-aminobutyric acid aminotransferase by gabaculine. Bioorg Med Chem 1999; 7:1581-90. [PMID: 10482450 DOI: 10.1016/s0968-0896(99)00081-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Gabaculine (5-amino-1,3-cyclohexadienylcarboxylic acid, 1), a naturally occurring neurotoxin isolated from Streptomyces toyocaenis, has been shown to be a mechanism-based inactivator of gamma-aminobutyric acid aminotransferase (GABA-AT) (Rando, R. R. Biochemistry 1977, 16, 4604). Inactivation results from reaction of gabaculine with the pyridoxal 5'-phosphate (PLP) cofactor. Two HPLC systems for isolating this inactivator-PLP adduct are described as well as a detailed characterization of the adduct, including the ultraviolet-visible spectrum, electrospray mass spectra, and NMR spectrum. The same spectral characterization of the chemically synthesized gabaculine-PLP adduct is also reported.
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Affiliation(s)
- M Fu
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
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32
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N'Gouemo P, Faingold CL. The periaqueductal grey is a critical site in the neuronal network for audiogenic seizures: modulation by GABA(A), NMDA and opioid receptors. Epilepsy Res 1999; 35:39-46. [PMID: 10232793 DOI: 10.1016/s0920-1211(98)00128-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The nuclei comprising the neuronal network for audiogenic seizures (AGS) are located primarily in the brainstem. Previous studies suggested a role for the periaqueductal grey (PAG) in the AGS network. The present study evaluated this possibility in genetically-epilepsy prone rats (GEPR-9s) by examining the effects of bilateral focal microinjection of a competitive NMDA receptor antagonist (DL-2-amino-7-phosphonoheptanoic acid (AP7), 1 and 5 nmol/side), a GABA(A) agonist (gaboxedol (THIP), 10 and 15 nmol) or an opioid peptide receptor antagonist (naloxone, 5 nmol) into PAG, based on the proposed role of these receptors in PAG neurotransmission. Blockade of NMDA receptors by AP7 (both doses) or activation of GABA(A) receptors with THIP (15 nmol/side) in the PAG suppressed AGS susceptibility. Naloxone displayed a seizure-suppressant effect that was delayed and incomplete. The seizure suppressant effect of AP7 or naloxone, unlike THIP, was observed at doses that did not produce motor quiescence. These data suggest that the PAG is a requisite nucleus in the neuronal network for AGS in GEPR-9s and that GABA(A), opioid peptide and NMDA receptors in the PAG modulate AGS propagation.
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Affiliation(s)
- P N'Gouemo
- Department of Pharmacology Southern Illinois University School of Medicine, Springfield 62794-9629, USA
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33
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Abstract
The Long-Evans rat is a hybrid rodent strain with little innate susceptibility to audiogenic seizures (AGS). The present study examines parameters of acoustic priming (induced susceptibility) and testing for AGS during postnatal development subsequent to auditory function, and identifies the effects of stimulus intensity, repeated testing, and gender upon AGS activity. Rats were exposed to 125-dB SPL 10-kHz tone bursts at 14-36 days of age and tested with white noise at 14 or 19 days following sound exposure. All priming/testing combinations yielded AGS susceptibility; animals primed at 18 days showed the highest incidence of clonic seizures when tested 14 days later. All subjects displayed clonus at testing intensities of 120 dB, although some seizure behaviors could be elicited at 100 dB. Repeated testing at 120 dB increased latency to clonus and clonus duration, and total wild running activity. Gender differences for AGS expression were minimal. These results demonstrate the viability of the seizure-resistant Long-Evans rat for study of AGS.
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Affiliation(s)
- K C Ross
- Department of Psychology, University of South Carolina, Columbia 29208, USA
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34
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Faingold C, Casebeer D. Modulation of the audiogenic seizure network by noradrenergic and glutamatergic receptors of the deep layers of superior colliculus. Brain Res 1999; 821:392-9. [PMID: 10064826 DOI: 10.1016/s0006-8993(99)01101-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Recent studies suggest that the deep layers of superior colliculus (DLSC) play a role in the network for audiogenic seizures (AGS) in genetically epilepsy-prone rats (GEPR-9s). The present study examined the role of glutamatergic and noradrenergic receptors in DLSC in modulation of AGS susceptibility. The study examined effects of a competitive NMDA receptor antagonist [dl-2-amino-7-phosphonoheptanoic acid (AP7)] or an alpha1 noradrenergic agonist (phenylephrine) focally microinjected into DLSC as compared to effects in the inferior colliculus (IC) and pontine reticular formation (PRF), which are major established components of the AGS network. The results demonstrated that blockade of NMDA receptors in DLSC suppressed AGS susceptibility. AP7 microinjection was effective at relatively low doses in IC, but required higher doses in DLSC and PRF. The DLSC was relatively more sensitive to seizure reduction by the alpha1 noradrenergic agonist as compared to the IC and PRF. The anticonvulsant effect of AP7 was longer-lasting than phenylephrine in the DLSC and IC but not in the PRF. These data suggest that neurons in the DLSC are a requisite component for the neuronal network for AGS in GEPR-9s and that NMDA and alpha1 adrenoreceptors in this site may play important roles in the modulation of AGS propagation. The relatively greater sensitivity of DLSC to phenylephrine as compared to IC and PRF indicates that norepinephrine may be more important in the modulation of AGS in DLSC, which contrasts to the role of glutamate modulation. These data support recent neuronal recording data, which indicate that DLSC neurons play a critical role in AGS.
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Affiliation(s)
- C Faingold
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA.
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35
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Silveira DC, Schachter SC, Schomer DL. Acoustic brainstem nuclei express Fos after flurothyl-induced generalized seizures in rats. Epilepsy Res 1999; 34:49-55. [PMID: 10194112 DOI: 10.1016/s0920-1211(98)00089-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The inferior colliculus (IC) plays a key role in modulating audiogenic seizures (AS) in rats. We investigated whether acoustic brainstem nuclei express Fos-like immunoreactivity (FLI) after flurothyl-induced generalized seizures in rats. Compared to controls, experimental animals showed significantly (P<0.05) more FLI in the dorsal and external cortex of the IC, as well as in the medial part of the medial geniculate body (MGB), perigeniculate area, and dorsal cochlear nucleus. No significant increase of FLI was observed in the central nucleus of the IC, ventral and dorsal parts of the MGB, dorsal nucleus of the lateral lemniscus, or ventral cochlear nucleus. Because this pattern of FLI closely resembles that observed after AS in previous studies, these results suggest that Fos expression in acoustic brainstem nuclei is not specific for AS.
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Affiliation(s)
- D C Silveira
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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36
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Faingold CL, Randall ME. Neurons in the deep layers of superior colliculus play a critical role in the neuronal network for audiogenic seizures: mechanisms for production of wild running behavior. Brain Res 1999; 815:250-8. [PMID: 9878768 DOI: 10.1016/s0006-8993(98)01136-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Recent investigations suggest that the deep layers of superior colliculus (DLSC) play a role in the neuronal network for audiogenic seizures (AGS). The present study examined DLSC neuronal firing and convulsive behavior simultaneously in freely-moving genetically epilepsy-prone rats (GEPR-9s) using chronically implanted microwire electrodes. An abrupt onset of acoustically-evoked firing at approximately 80-90 dB was observed in DLSC neurons of GEPR-9s, which was significantly above the normal threshold. DLSC neurons began to exhibit rapid tonic burst firing 1-2 s prior to the onset of the wild running behavior at the beginning of AGS. As the tonic phase of the seizure began, DLSC firing ceased, and only returned towards normal following post-ictal depression. These neuronal mechanisms may be relevant to other seizure models in which the DLSC is implicated. The temporal pattern of neuronal firing during AGS is specific to DLSC and differs markedly from those observed elsewhere in the AGS neuronal network. The temporal firing pattern suggests that the DLSC plays a primary role in the generation of the wild running phase of AGS. Previous studies indicate that the inferior colliculus is dominant during AGS initiation, and the pontine reticular formation is dominant during the tonic extension phase of AGS. Taken together these data suggest that the neurons in the neuronal network undergo a dominance shift as each specific convulsive behavior of AGS is elaborated.
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Affiliation(s)
- C L Faingold
- Department of Pharmacology, P.O. Box 19629, Southern Illinois University School of Medicine, Springfield, IL 62794-9629, USA.
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Goei VL, Choi J, Ahn J, Bowlus CL, Raha-Chowdhury R, Gruen JR. Human gamma-aminobutyric acid B receptor gene: complementary DNA cloning, expression, chromosomal location, and genomic organization. Biol Psychiatry 1998; 44:659-66. [PMID: 9798068 DOI: 10.1016/s0006-3223(98)00244-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The 6p21.3 region of human chromosome 6 is a genetic locus for schizophrenia, juvenile myoclonic epilepsy, and dyslexia. METHODS Due to our interest in these disorders we performed complementary DNA (cDNA) hybridization selection on genomic DNA clones spanning this region to identify potential positional-candidate genes. RESULTS We identified a full-length cDNA with an open reading frame of 2883 bp corresponding to a predicted protein of 961 amino acids that shares greater than 95% homology with the rat gamma-aminobutyric acid B (GABAB) receptor. Northern blot hybridization identified a 4.4-kb transcript in human brain. The human gene mapped to two sites on 6p21.3 separated by 2 Mb. Sequence analysis of both sites showed that the centromeric gene is transcribed, whereas the telomeric site is likely a pseudogene. The transcribed gene is distributed over 22 exons spanning 18 kb of genomic DNA. CONCLUSIONS The genomic location, tissue expression, and function of the human GABAB receptor gene suggest that it is an important positional-candidate for the neurobehavioral disorders with a genetic locus on 6p21.3. In addition, delineation of the genomic organization will now permit it to be integrated as part of pharmacogenetic studies in trials of anxiolytic, narcotic, antiepileptic, and fluoxetine therapies.
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Affiliation(s)
- V L Goei
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06517, USA
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38
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Grifa A, Totaro A, Rommens JM, Carella M, Roetto A, Borgato L, Zelante L, Gasparini P. GABA (gamma-amino-butyric acid) neurotransmission: identification and fine mapping of the human GABAB receptor gene. Biochem Biophys Res Commun 1998; 250:240-5. [PMID: 9753614 DOI: 10.1006/bbrc.1998.9296] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
GABA (gamma-amino-butyric acid) receptors are a family of proteins involved in the GABAergic neurotransmission of the mammalian central nervous system (CNS). They have physiological importance and clinical relevance in several diseases. We report the identification, cloning, and fine mapping of the human cDNA for GABAB receptor. A 4.2-Kb cDNA containing an open reading frame for a predicted protein of 960 aa was isolated from a fetal brain cDNA library. It had a strong identity (91.5%) with the rat GABAB receptor (rGB1A) nucleotide sequence, that corresponded to 98.6% identity at the amino acid level. Expression of the GABAB at the transcription level was detected by Northern analysis in all brain areas examined. The GABAB receptor has been mapped to human chromosome 6p21.3 within the HLA class I region close to the HLA-F gene. Susceptibility loci for multiple sclerosis, epilepsy, and schizophrenia have been suggested to map in this region.
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Affiliation(s)
- A Grifa
- Servizio di Genetica Medica, IRCCS-Ospedale CSS San Giovanni Rotondo, Italy
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Faingold CL, N'Gouemo P, Riaz A. Ethanol and neurotransmitter interactions--from molecular to integrative effects. Prog Neurobiol 1998; 55:509-35. [PMID: 9670216 DOI: 10.1016/s0301-0082(98)00027-6] [Citation(s) in RCA: 201] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
There is extensive evidence that ethanol interacts with a variety of neurotransmitters. Considerable research indicates that the major actions of ethanol involve enhancement of the effects of gamma-aminobutyric acid (GABA) at GABAA receptors and blockade of the NMDA subtype of excitatory amino acid (EAA) receptor. Ethanol increases GABAA receptor-mediated inhibition, but this does not occur in all brain regions, all cell types in the same region, nor at all GABAA receptor sites on the same neuron, nor across species in the same brain region. The molecular basis for the selectivity of the action of ethanol on GaBAA receptors has been proposed to involve a combination of benzodiazepine subtype, beta 2 subunit, and a splice variant of the gamma 2 subunit, but substantial controversy on this issue currently remains. Chronic ethanol administration results in tolerance, dependence, and an ethanol withdrawal (ETX) syndrome, which are mediated, in part, by desensitization and/or down-regulation of GABAA receptors. This decrease in ethanol action may involve changes in subunit expression in selected brain areas, but these data are complex and somewhat contradictory at present. The sensitivity of NMDA receptors to ethanol block is proposed to involve the NMDAR2B subunit in certain brain regions, but this subunit does not appear to be the sole determinant of this interaction. Tolerance to ethanol results in enhanced EAA neurotransmission and NMDA receptor upregulation, which appears to involve selective increases in NMDAR2B subunit levels and other molecular changes in specific brain loci. During ETX a variety of symptoms are seen, including susceptibility to seizures. In rodents these seizures are readily triggered by sound (audiogenic seizures). The neuronal network required for these seizures is contained primarily in certain brain stem structures. Specific nuclei appear to play a hierarchical role in generating each stereotypical behavioral phases of the convulsion. Thus, the inferior colliculus acts to initiate these seizures, and a decrease in effectiveness of GABA-mediated inhibition in these neurons is a major initiation mechanism. The deep layers of superior colliculus are implicated in generation of the wild running behavior. The pontine reticular formation, substantia nigra and periaqueductal gray are implicated in generation of the tonic-clonic seizure behavior. The mechanisms involved in the recruitment of neurons within each network nucleus into the seizure circuit have been proposed to require activation of a critical mass of neurons. Achievement of critical mass may involve excess EAA-mediated synaptic neurotransmission due, in part, to upregulation as well as other phenomena, including volume (non-synaptic diffusion) neurotransmission. Effects of ETX on receptors observed in vitro may undergo amplification in vivo to allow the excess EAA action to be magnified sufficiently to produce synchronization of neuronal firing, allowing participation of the nucleus in seizure generation. GABA-mediated inhibition, which normally acts to limit excitation, is diminished in effectiveness during ETX, and further intensifies this excitation.
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Affiliation(s)
- C L Faingold
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62794-1222, USA
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Akbar MT, Rattray M, Williams RJ, Chong NW, Meldrum BS. Reduction of GABA and glutamate transporter messenger RNAs in the severe-seizure genetically epilepsy-prone rat. Neuroscience 1998; 85:1235-51. [PMID: 9681960 DOI: 10.1016/s0306-4522(97)00684-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The genetically epilepsy-prone rat is an animal model of inherited generalised tonic-clonic epilepsy that shows abnormal susceptibility to audiogenic seizures and a lowered threshold to a variety of seizure-inducing stimuli. Recent studies suggest a crucial role for glutamate and GABA transporters in epileptogenesis and seizure propagation. The present study examines the levels of expression of the messenger RNAs encoding the glial and neuronal glutamate transporters, GLT-1 and EAAC-1, and the neuronal GABA transporter, GAT-1, in paired male genetically epileptic-prone rats and Sprague Dawley control rats using the technique of in situ hybridization. In a parallel study, semiquantitative immunoblotting was used to assess GLT-1 and EAAC-1 protein levels in similarly paired animals. Animals were assessed for susceptibility to audiogenic seizures on six occasions, and killed seven days following the last audiogenic stimulus exposure. Rat brains were processed for in situ hybridization with radioactive 35S-labelled oligonucleotide probes (EAAC-1 and GAT-1), 35S-labelled riboprobes (GLT-1), and Fluorescein-labelled riboprobes (GLT-1 and GAT-1) or processed for immunoblotting using subtype-specific antibodies for GLT-1 and EAAC-1. Semiquantitative analyses were carried out on X-ray film autoradiograms in several brain regions for both in situ hybridization and immunoblotting studies. Reductions in GAT-1 messenger RNA were found in genetically epileptic-prone rats in all brain regions examined (-8 to -24% compared to control). Similar reductions in GLT-1 messenger RNA expression levels were seen in cortex, striatum, and CA1 (-8 to -12%) of genetically epileptic-prone rats; the largest reduction observed was in the inferior colliculus (-20%). There was a tendency for a reduced expression of EAAC-1 messenger RNA in most regions of the genetically epileptic-prone rat brain although this reached statistical significance only in the striatum (-12%). In contrast, no significant differences in GLT-1 and EAAC-1 protein between genetically epileptic-prone rats and control animals were observed in any region examined, although there was a tendency to follow the changes seen with the corresponding messenger RNAs. These results show differences in the messenger RNA expression levels of three crucial amino acid transporters. For the two glutamate transporters, GLT-1 and EAAC-1, differences in messenger RNA levels are not reflected or are only partially reflected in the expression of the corresponding proteins.
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Affiliation(s)
- M T Akbar
- Department of Clinical Neurosciences, Institute of Psychiatry, London, UK
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Magnesium deficiency-dependent audiogenic seizures (MDDASs) in adult mice: a nutritional model for discriminatory screening of anticonvulsant drugs and original assessment of neuroprotection properties. J Neurosci 1998. [PMID: 9592113 DOI: 10.1523/jneurosci.18-11-04363.1998] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A great many animal models for audiogenic seizures have been described. The extent to which these models may provide insight into neuroscience fields such as abnormal locomotor behavior (wild running), seizures and anticonvulsants, and neuroinsults and neuroprotectors is examined here by our study of magnesium deficiency-dependent audiogenic seizures (MDDASs) in adult mice. MDDASs were induced in all of the eight tested adult murine strains and are presented as a sequence of four successive components (latency, wild running, convulsion, and recovery phase periods). Compared with several classic seizure tests, the nutritional MDDAS model responded to low doses of prototype antiepileptic drugs (AEDs), including phenytoin (PHT), carbamazepine (CBZ), phenobarbital (PB), valproic acid (VPA), ethosuximide (ESM), and diazepam (DZP). Modulation by AEDs of the four components of MDDAS indicated that this seizure test was discriminatory, distinguishing between phenytoinergic (PHT, CBZ), GABAergic (PB, VPA, DZP), and ethosuximide (ESM) compounds. Suitability of the MDDAS test for evaluation of neuroprotective compounds was also examined: it showed partial (melatonin) and complete (WEB2170, an anti-PAF agent) reduction of recovery phase by non-anticonvulsant doses of test compounds. These neuroprotective responses were compared with neuroprotective potentials determined in a model of neonatal cerebral injury induced by focal injection of ibotenate (a glutamate analog). WEB2170 and melatonin reduced the size of lesions in white matter, but only WEB2170 protected cortical plate against ibotenate-induced lesions. In addition to the original neuroprotective behavior of WEB2170, studies on the neuroprotectors also supported GABAergic anticonvulsant activity of melatonin in the MDDAS test.
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Abstract
Immunocytochemistry was used to study the distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subtypes in the inferior colliculus (IC) of genetically epilepsy-prone rats (GEPR-9s) and normal Sprague-Dawley (SD) rats. The analysis was conducted using 3 antibodies specific for glutamate receptor subtypes, GluR 1, GluR 2/3, and GluR 4. Light microscopy showed that immunostaining of the IC was most dense with the GluR 2/3 antibody for both strains of animals. The amount of GluR 2/3 immunolabeling was similar for sound-stimulated GEPR-9s, seizure-naive GEPR-9s, and SD rats. The electron microscopy of GluR 2/3 in the IC revealed immunoreaction products associated with the postsynaptic densities of asymmetric synapses. The thin sections had comparable amounts of reaction product in dendrites or dendritic spines for both strains. Since the distribution and quantity of AMPA receptors in the IC of GEPR-9s and SD rats are similar, our results indicate that altered AMPA receptors are probably not the primary cause of seizure initiation in GEPR-9s.
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Affiliation(s)
- W C Gaza
- Department of Anatomy and Neurobiology, University of California at Irvine, 92697, USA
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43
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Vergnes M, Boehrer A, Simler S, Bernasconi R, Marescaux C. Opposite effects of GABAB receptor antagonists on absences and convulsive seizures. Eur J Pharmacol 1997; 332:245-55. [PMID: 9300256 DOI: 10.1016/s0014-2999(97)01085-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In Wistar rats with spontaneous non-convulsive absence epilepsy, absence seizures were dose dependently suppressed by intraperitoneal administration of the GABAB receptor antagonists CGP 36742, 50-400 mg/kg, and CGP 56999, 0.25-0.75 mg/kg, and by bilateral microinjections of the same compounds into the lateral nuclei of the thalamus. In rats susceptible to audiogenic seizures, intraperitoneal administration of both GABAB receptor antagonists, at doses which suppressed absence seizures, facilitated the elicitation of sound-induced tonic seizures. In non-epileptic control rats, intraperitoneal injections of higher doses of CGP 36742 (800-2400 mg/kg) and CGP 56999 (3-6 mg/kg) induced delayed clonic convulsions, which were suppressed by pretreatment with baclofen. c-Fos protein was expressed after GABAB receptor antagonist-induced seizures in the cortex, hippocampus, amygdala, perirhinal and piriform cortex. Intra-cortical and hippocampal microinfusion of both GABAB receptor antagonists produced focal seizures. In conclusion, GABAB receptor antagonists suppress non-convulsive absence seizures by blocking thalamic GABAB receptors, while they induce convulsions in cortical and limbic structures.
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Affiliation(s)
- M Vergnes
- Unité INSERM 398, Faculté de Médecine, Strasbourg, France.
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44
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Chakravarty DN, Faingold CL. Aberrant neuronal responsiveness in the genetically epilepsy-prone rat: acoustic responses and influences of the central nucleus upon the external nucleus of inferior colliculus. Brain Res 1997; 761:263-70. [PMID: 9252025 DOI: 10.1016/s0006-8993(97)00331-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The inferior colliculus (IC) central nucleus (ICc), is critical for audiogenic seizure (AGS) initiation in the genetically epilepsy-prone rat (GEPR). The ICc lacks direct motor outputs but sends a major projection to the external nucleus of IC (ICx), which does project to the sensorimotor integration nuclei within the AGS neuronal network. The present study compared acoustic responses of ICx neurons in the GEPR and normal anesthetized rat and evaluated whether the GEPR exhibits functional abnormalities in the pathway from ICc to ICx. There is a significantly greater incidence of sustained repetitive response patterns to the acoustic stimulus in GEPR ICx neurons (75%) than in normal ICx neurons (24%). Following unilateral microinjection of N-methyl-D-aspartate (NMDA) into the contralateral ICc, acoustically-evoked ICx excitation and inhibition were each increased in normal animals, which is consistent with the mixed projections previously reported in this pathway and observed with electrical stimulation in the present study. The NMDA-induced ICx firing increase may be relevant to AGS, since, in previous studies, bilateral focal microinjection of NMDA into the ICc induced AGS susceptibility in normal rats [23]. However, the incidence and degree of the ICx neuronal response changes after NMDA microinjection was not abnormal in the GEPR. These data suggest that the hyperresponsiveness of ICx neurons may not involve abnormal transmission between the ICc and ICx, despite the elevated ICx neuronal responses to acoustic stimuli. However, the ICx hyperresponsivess of the GEPR, which is likely due to the known decrease in effectiveness of GABA-mediated inhibition in GEPR neurons, may be a major mechanism subserving the critical role that this structure plays in the AGS network.
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Affiliation(s)
- D N Chakravarty
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62794-1222, USA
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45
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Dalby NO, Thomsen C, Fink-Jensen A, Lundbeck J, Søkilde B, Man CM, Sørensen PO, Meldrum B. Anticonvulsant properties of two GABA uptake inhibitors NNC 05-2045 and NNC 05-2090, not acting preferentially on GAT-1. Epilepsy Res 1997; 28:51-61. [PMID: 9255599 DOI: 10.1016/s0920-1211(97)00033-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Two novel nipecotic acid derivatives, 1-(3-(9H-Carbazol-9-yl)-1-propyl)-4-(4-methoxyphenyl)-4-piperidino l (NNC 05-2045) and 1-(3-(9H-Carbazol-9-yl)-l-propyl)-4-(2-methoxyphenyl)-4-piperidino l (NNC 05-2090) have been tested for inhibition of gamma-amino butyric acid (GABA) transporters in synaptosomal preparations of rat cerebral cortex and inferior colliculus and found to differ markedly from gabitril (tiagabine), a selective GAT-1 inhibitor. IC50 values for inhibition of [3H]GABA uptake into synaptosomes from cerebral cortex for NNC 05-2045 and NNC 05-2090 were 12 +/- 2 and 4.4 +/- 0.8 microM, respectively. In synaptosomes from inferior colliculus in the presence of 1 microM 1-(2-(((diphenylmethylene)amino)oxy)ethyl)-1,2,5,6-tetrahydro-3- pyridinecarboxylic acid (NNC 05-0711), a highly potent and selective GAT-1 inhibitor, IC50 values for inhibition of [3H]GABA uptake were 1.0 +/- 0.1 and 2.5 +/- 0.7 microM, respectively. A receptor profile showed that NNC 05-2045 has binding affinities to sigma-, alpha 1- and D2-receptors of 113, 550 and 122 nM, respectively. NNC 05-2090 displayed alpha 1- and D2-receptor affinity of 266 and 1632 nM, respectively. The anticonvulsant action of both compounds was tested in four rodent models after intra peritoneal (i.p.) injection. Both NNC 05-2090 dose-dependently inhibited sound-induced tonic and clonic convulsions in DBA/2 mice with ED50 values of 6 and 19 mumol/kg, respectively. NNC 05-2045 also antagonized sound-induced seizures in genetic epilepsy prone rats (GEP rats) with ED50 values against wild running, clonic and tonic convulsions of 33, 39 and 39 mumol/kg, respectively (NNC 05-2090 was not tested in GEP rats). Both NNC 05-2045 and NNC 05-2090 dose-dependently antagonized tonic hindlimb extension in the maximal electroshock (MES) test with ED50 values of 29 and 73 mumol/kg, respectively. In amygdala kindled rats NNC 05-2045 and NNC 05-2090 significantly (P < 0.05) reduced generalized seizure severity (seizure grade 3-5) at highest doses (72-242 mumol/kg) and NNC 05-2090 also significantly reduced afterdischarge duration at these doses (P < 0.05). These data show that inhibition of GABA uptake through non-GAT-1 transporters has different anticonvulsant effects than selective GAT-1 inhibitors (e.g. tiagabine) in that enhanced efficacy against MES and reduced efficacy against kindled seizures is observed. Although a contribution of adrenergic agonistic effects cannot be entirely ruled out, it is proposed that inhibition of GAT-3 (mouse GAT4) is primarily responsible for the anticonvulsant action of these two nipecotic acid derivatives in MES, amygdala kindled rats and in sound-induced seizures in GEP-rats and DBA/2 mice.
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46
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Ribak CE, Manio AL, Navetta MS, Gall CM. In situ hybridization for c-fos mRNA reveals the involvement of the superior colliculus in the propagation of seizure activity in genetically epilepsy-prone rats. Epilepsy Res 1997; 26:397-406. [PMID: 9127720 DOI: 10.1016/s0920-1211(96)01011-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Previous work showed that bilateral lesions made between the inferior and superior colliculi reduced the severity of audiogenic seizures in genetically epilepsy-prone rats (GEPR-9s), and indicated that the connections between these two structures are vital for the propagation of seizure activity. To determine the involvement of the superior colliculus (SC) in seizure propagation, GEPR-9s were given four audiogenic seizures within 1 h by ringing a loud bell, and their brains were processed 30 min later for in situ hybridization for c-fos mRNA. Brain sections from such rats showed dense labeling in both the dorsal cortex and external nucleus of the inferior colliculus. Labeling continued rostrally into the intermediate and deep layers of the SC and the periaqueductal gray region. In addition, other brain regions such as the amygdala, piriform cortex and dorsal endopiriform nucleus showed dense labeling for c-fos mRNA. Comparable increases were not observed in the brains of Sprague-Dawley (SD) rats receiving auditory stimulation or in unstimulated GEPR-9s and SD rats, thereby indicating that increases in stimulated GEPR-9s are seizure-specific. This study provides further evidence that the SC is involved in the propagation of seizure activity in GEPR-9s, and also demonstrates the activation of other brain regions by audiogenic seizures.
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Affiliation(s)
- C E Ribak
- Department of Anatomy and Neurobiology, University of California, Irvine 92717, USA.
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47
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Peterson SL. The effect on maximal electroshock seizures induced by GABA agents and antiepileptic drugs microinfused into the nucleus reticularis pontis oralis. Epilepsy Res 1996; 25:161-7. [PMID: 8956912 DOI: 10.1016/s0920-1211(96)00069-1] [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: 02/03/2023]
Abstract
The nucleus reticularis pontis oralis (RPO) is necessary for the expression of tonic hindlimb extension (THE) in maximal electroshock seizures (MES) of rats. Previous work in this laboratory has demonstrated that focal RPO microinfusion of NMDA antagonists inhibited THE while focal RPO microinfusion of NMDA induced convulsive activity similar to the audiogenic seizure response of rats. The purpose of the present study was to identify other receptors in the RPO that influence THE or induce convulsive activity. Bilateral microinfusion of bicuculline had no effect on the THE component of MES except when the bicuculline induced wild-running convulsions in which case the subsequent THE response to the MES stimulus was inhibited. The GABAergic agents muscimol, baclofen or 2-hydroxysaclofen neither altered the THE response nor induced convulsions. In addition, bilateral RPO microinfusion of the clinically effective antiepileptic drugs phenytoin, phenobarbital, valproate, ethosuximide or felbamate had no effect on the THE component of MES. These results indicate that the role of GABAergic receptors in the anticonvulsant activity mediated by the RPO is not prominent and that the RPO is unlikely to be the site of antiepileptic drug action in MES.
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Affiliation(s)
- S L Peterson
- College of Pharmacy, University of New Mexico Health Science Center, Albuquerque 87131-1066, USA
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48
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Kanthasamy AG, Vu TQ, Yun RJ, Truong DD. Antimyoclonic effect of gabapentin in a posthypoxic animal model of myoclonus. Eur J Pharmacol 1996; 297:219-24. [PMID: 8666053 DOI: 10.1016/0014-2999(95)00741-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The antimyoclonic property of the novel antiepileptic drug, gabapentin (1-(aminomethyl) cyclohexane acetic acid), was tested in cardiac arrest-and p,p'-DDT(1,1,1-trichloro-2,2-bis (p-chlorophenyl)ethane)-induced animal models of myoclonus. Gabapentin dose-dependently attenuated myoclonus in posthypoxic rats for more than 3 h. The drug was also found to be effective in controlling the early stages of seizures following the anoxic insult. In contrast, the drug was ineffective in controlling either myoclonus or seizures in p,p'-DDT-treated animals. These results suggest that gabapentin can be used used as an effective therapeutic agent in an acute hypoxia/ischemia-induced neurological disorder. The data further indicate that distinct neurological mechanisms may be operating in the expression of myoclonus among posthypoxic and p,p'-DDT-induced animal models.
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Affiliation(s)
- A G Kanthasamy
- Department of Neurology, College of Medicine, University of California Irvine 92717, USA
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49
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Coffey LL, Reith ME, Chen NH, Mishra PK, Jobe PC. Amygdala kindling of forebrain seizures and the occurrence of brainstem seizures in genetically epilepsy-prone rats. Epilepsia 1996; 37:188-97. [PMID: 8635430 DOI: 10.1111/j.1528-1157.1996.tb00011.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Forebrain seizures were kindled in rats by daily electrical stimulation of the amygdala. Genetically epilepsy-prone rats scoring 9 (GEPR-9s) on the seizure severity scale during audiogenic seizure (AGS) screening ("brainstem seizure-experienced") required fewer stimulations to achieve fully kindled seizures (forelimb clonus with rearing and falling) than control rats. AGS-naive GEPR-9s required an intermediate number of stimulations, indicating a role for both genetic predisposition and previous acoustically evoked brainstem seizure experience. Other forebrain kindling indices such as afterdischarge threshold/duration and seizure latency/duration also involved genetic as well as phenotypic (previous seizure experience) factors. In most GEPR-9s in both groups, severe brainstem seizures occurred after forebrain stimulation. The occurrence of brainstem seizures had a random nature and was not related to the sequence of kindling-dependent forebrain seizure progression. The lack of a difference in the occurrence of brainstem seizures between seizure-experienced and AGS-naive GEPR-9s suggest that genetic predisposition is the major factor in forebrain seizure-induced activation of brainstem seizure circuitry. This brainstem seizure activity appears to model pertinent aspects of secondary generalization observed in human partial seizures.
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Affiliation(s)
- L L Coffey
- Department of Biomedical and Therapeutic Sciences (Formerly Basic Sciences), University of Illinois College of Medicine, Peoria 61656, USA
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50
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Faingold CL, Randall ME. Pontine reticular formation neurons exhibit a premature and precipitous increase in acoustic responses prior to audiogenic seizures in genetically epilepsy-prone rats. Brain Res 1995; 704:218-26. [PMID: 8788917 DOI: 10.1016/0006-8993(95)01116-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The genetically epilepsy-prone rat (GEPR-9) exhibits elevated seizure sensitivity and audiogenic seizures (AGS). The pontine reticular formation (PRF) is implicated in the neuronal network for AGS in the GEPR-9. The present study examined PRF neuronal firing and convulsive behavior simultaneously in the GEPR-9. Chronically implanted microwire electrodes in PRF allowed single neuronal responses and behavior to be examined in freely-moving rats. PRF neurons in the GEPR-9 exhibit precipitous intensity-evoked increases at a significantly lower (approx. 15 dB SPL) intensity than normal Sprague-Dawley rats. PRF neurons in the GEPR-9 also exhibit increased auditory response latencies. At the onset of AGS (wild running) the firing rate of PRF neurons increased, and the rate of PRF firing increased dramatically as the tonic phase of the seizure began. During post-ictal depression the rate of PRF neuronal firing slowed, gradually returning to normal. This pattern of PRF periseizural neuronal firing changes differ dramatically in pattern and temporal characteristics from those previously observed in inferior colliculus (IC). The IC serves as the AGS initiation site. IC neurons show extensive firing increases prior to and during the initial wild running, silence during the tonic and post-ictal phases, and gradual recovery of responses thereafter. The changes in PRF neuronal firing pattern suggest that the PRF may play a major role in the generation of the tonic phase of AGS. The premature onset of the precipitous rise in PRF neuronal firing suggests that the influence of the IC on PRF neurons may be magnified in association with AGS susceptibility. The PRF neuronal firing increases observed in the present study coupled with previous observation of AGS blockade by PRF microinjections in the GEPR-9 further support an important role of the PRF in the propagation of AGS in the GEPR-9. The mechanisms of PRF firing elevation may also be relevant in other seizure models in which the brain-stem reticular formation is implicated.
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Affiliation(s)
- C L Faingold
- Department of Pharmacology, Southern Illinois University, Springfield 62794-9230, USA
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