1
|
Bekbolatova M, Mayer J, Jose R, Syed F, Kurgansky G, Singh P, Pao R, Zaw H, Devine T, Chan-Akeley R, Toma M. Biomechanical Effects of Seizures on Cerebral Dynamics and Brain Stress. Brain Sci 2024; 14:323. [PMID: 38671975 PMCID: PMC11048267 DOI: 10.3390/brainsci14040323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 03/22/2024] [Accepted: 03/26/2024] [Indexed: 04/28/2024] Open
Abstract
Epilepsy is one of the most common neurological disorders globally, affecting about 50 million people, with nearly 80% of those affected residing in low- and middle-income countries. It is characterized by recurrent seizures that result from abnormal electrical brain activity, with seizures varying widely in manifestation. The exploration of the biomechanical effects that seizures have on brain dynamics and stress levels is relevant for the development of more effective treatments and protective strategies. This study uses a blend of experimental data and computational simulations to assess the brain's physical response during seizures, particularly focusing on the behavior of cerebrospinal fluid and the resulting mechanical stresses on different brain regions. Notable findings show increases in stress, predominantly in the posterior gyri and brainstem, during seizures and an evidence of brain displacement relative to the skull. These observations suggest a dynamic and complex interaction between the brain and skull, with maximum shear stress regions demonstrating the limited yet essential protective role of the CSF. By providing a deeper understanding of the mechanical changes occurring during seizures, this research supports the goal of advancing diagnostic tools, informing more targeted treatment interventions, and guiding the creation of customized therapeutic strategies to enhance neurological care and protect against the adverse effects of seizures.
Collapse
Affiliation(s)
- Molly Bekbolatova
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| | - Jonathan Mayer
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| | - Rejath Jose
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| | - Faiz Syed
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| | - Gregory Kurgansky
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| | - Paramvir Singh
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| | - Rachel Pao
- NewYork-Presbyterian Queens Hospital, New York City, NY 11355, USA;
| | - Honey Zaw
- Icahn School of Medicine at Mount Sinai, 1428 Madison Avenue, Atran Berg Building, 8th Floor, New York City, NY 10029, USA;
| | - Timothy Devine
- The Ferrara Center for Patient Safety and Clinical Simulation, Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA;
| | | | - Milan Toma
- Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA; (M.B.); (J.M.); (R.J.); (F.S.); (G.K.); (P.S.)
| |
Collapse
|
2
|
Functional, metabolic, and synaptic changes after seizures as potential targets for antiepileptic therapy. Epilepsy Behav 2010; 19:105-13. [PMID: 20705520 DOI: 10.1016/j.yebeh.2010.06.035] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 06/17/2010] [Indexed: 01/11/2023]
Abstract
Little is known about how the brain limits seizure duration and terminates seizures. Depending on severity and duration, a single seizure is followed by various functional, metabolic, and synaptic changes that may form targets for novel therapeutic strategies. It is long known that most seizures are followed by a period of postictal refractoriness during which the threshold for induction of additional seizures is increased. The endogenous anticonvulsant mechanisms involved in this phenomenon may be relevant for both spontaneous seizure arrest and increase of seizure threshold after seizure arrest. Postictal refractoriness has been extensively studied in various seizure and epilepsy models, including electrically and chemically induced seizures, kindling, and genetic animal models of epilepsy. During kindling development, two antagonistic processes occur simultaneously, one responsible for kindling-like events and the other for terminating ictus and postictal refractoriness. Frequently occurring seizures may lead to an accumulation of postictal refractoriness that may last weeks. The mechanisms involved in seizure termination and postictal refractoriness include changes in ionic microenvironment, in pH, and in various endogenous neuromodulators such as adenosine and neuropeptides. In animal models, the anticonvulsant efficacy of several antiepileptic drugs (AEDs) is increased during postictal refractoriness, which is a logical consequence of the interaction between endogenous anticonvulsant processes and the mechanism of AEDs. As discussed in this review, enhanced understanding of these endogenous processes may lead to novel targets for AED development.
Collapse
|
3
|
Mueller SG, Weber OM, Duc CO, Meier D, Russ W, Boesiger P, Wieser HG. Effects of vigabatrin on brain GABA+/Cr signals in focus-distant and focus-near brain regions monitored by 1H-NMR spectroscopy. Eur J Neurol 2003; 10:45-52. [PMID: 12534992 DOI: 10.1046/j.1468-1331.2003.00506.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The new antiepileptic drug vigabatrin (VGB) increases gamma-aminobutyric acid (GABA) in the brain. We compared GABA+/Cr signals measured focus-near and focus-distant and correlated it with the degree of response to VGB. Brain GABA+/Cr signals were measured in 17 epileptic patients in structurally normal appearing tissue by nuclear proton magnetic resonance (1H-NMR) spectroscopy using a special editing sequence for GABA. In 11 patients the measurements were done in brain areas distant to focus and in six near to focus. Full-responders (seizure reduction of >or=50% at the end of the treatment phase) and partial-responders (seizure reduction of >or=50% at the end of the first month of treatment but <or=50% at end of treatment) had lower GABA+/Cr signals in the hemisphere with the epileptogenic focus and increases of the GABA+/Cr signals with VGB. Non-responders (seizure reduction of <or=50%) had no side difference in the GABA+/Cr signals before treatment and no increase during treatment. These observations were made in structurally normal appearing tissue near to the focus and distant to the focus. A side difference in brain GABA+/Cr signal between the epileptogenic and non-epileptogenic hemisphere before VGB treatment correlates with an improved seizure control under VGB treatment regardless whether the measurement is done focus-near or focus-distant.
Collapse
Affiliation(s)
- S G Mueller
- Department of Neurology, University Hospital, Frauenklinikstr 26, CH-8091 Zurich
| | | | | | | | | | | | | |
Collapse
|
4
|
Rubaj A, Zgodziński W, Sieklucka-Dziuba M. The epileptogenic effect of seizures induced by hypoxia: the role of NMDA and AMPA/KA antagonists. Pharmacol Biochem Behav 2003; 74:303-11. [PMID: 12479949 DOI: 10.1016/s0091-3057(02)00998-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hypoxia of the brain may alter further seizure susceptibility in a different way. In this study, we tried to answer the question how episode of convulsion induced by hypoxia (HS) changes further seizure susceptibility, and how N-methyl-D-aspartic acid (NMDA) and AMPA/KA receptor antagonists influence this process. Adult Albino Swiss mice exposed to hypoxia (5% O(2)) developed clonic/tonic convulsions after about 340 s. Mice which underwent 10 s but not 5 s seizures episode subsequently exhibited significantly increased seizure susceptibility to low doses (equal ED(16)) of bicuculline (BCC) and NMDA during a 3-week observation period. No morphological signs of brain tissue damage were seen in light microscope on the third day after a hypoxia-induced seizure (HS). Learning abilities assessed in passive avoidance test as well as spontaneous alternation were not disturbed after an HS episode. Pretreatment with AMPA/KA receptor antagonist NBQX effectively prolonged latency to HS and given immediately after seizure episode also attenuated subsequent convulsive susceptibility rise, however, NMDA receptor antagonist, MK-801, appeared to be ineffective. These results suggest that a seizure episode induced by hypoxia, depending on its duration, may play an epileptogenic role. The AMPA/KA receptor antagonist prolongs the latency to HS, and given after this episode, prevents the long-term epileptogenic effect.
Collapse
Affiliation(s)
- Andrzej Rubaj
- Department of Cardiology, Medical University of Lublin, Jaczewskiego 8, 20-090 Lublin, Poland.
| | | | | |
Collapse
|
5
|
Green AR, Hainsworth AH, Jackson DM. GABA potentiation: a logical pharmacological approach for the treatment of acute ischaemic stroke. Neuropharmacology 2000; 39:1483-94. [PMID: 10854894 DOI: 10.1016/s0028-3908(99)00233-6] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
It has been shown that enhancing the function of the major inhibitory neurotransmitter GABA decreases glutamatergic activity in the brain. Since increased glutamatergic activity is the major primary event that results in cell death following an acute hypoxic-ischaemic stroke, GABAmimetic drugs might therefore be expected to be neuroprotective. This review examines the evidence that GABAergic function is acutely depressed following an ischaemic insult, and also reviews the data that suggest that increasing cerebral GABA concentration has a neuroprotective effect, as does the administration of some (but not all) GABAmimetic agents. The GABA uptake inhibitor CI-966, the GABA(A) agonist muscimol and the GABA(A)mimetic clomethiazole have all been shown to be neuroprotective in animal models of stroke when given after the ischaemic insult. In contrast, benzodiazepines and particularly barbiturates, although potent GABA(A) potentiators, have shown little promise as neuroprotectants. The diversity of GABA(A) receptor subtypes and the in vivo efficacy of certain GABA(A) receptor ligands in animal models of stroke suggests that GABAmimetic drugs are an undervalued approach to stroke therapy.
Collapse
Affiliation(s)
- A R Green
- AstraZeneca R&D Charnwood, Bakewell Rd, LE11 5RH, Loughborough, UK.
| | | | | |
Collapse
|
6
|
Fisher RS, Schachter SC. The postictal state: a neglected entity in the management of epilepsy. Epilepsy Behav 2000; 1:52-9. [PMID: 12609127 DOI: 10.1006/ebeh.2000.0023] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/1999] [Accepted: 01/21/2000] [Indexed: 11/22/2022]
Abstract
Some of the disability deriving from epilepsy derives from the postictal state (PS). The PS may be complicated by impaired cognition, headache, injuries, or secondary medical conditions. Postictal depression is common, postictal psychosis relatively rare, but both add to the morbidity of seizures. The mechanisms of the PS are poorly understood. Alteration of cerebral blood flow both results from and contributes to the PS. Many neurotransmitters or neuromodulators are involved in the physiology of the PS. Response to glutamate may partially desensitize after a seizure. Endogenous opiates and adenosine serve as natural antiepileptic medications in some circumstances. Nitric oxide has numerous effects on brain excitability, and may be particularly important in regulating postictal cerebral blood flow. Just as the pathophysiology of seizures is complicated, so is that of the PS multifactorial. As a practical issue, it would be very useful to have medications that reduce the morbidity of the PS.
Collapse
Affiliation(s)
- R S Fisher
- Barrow Neurological Institute and University of Arizona, Phoenix, Arizona
| | - S C Schachter
- Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| |
Collapse
|
7
|
Sperber EF, Haas KZ, Romero MT, Stanton PK. Flurothyl status epilepticus in developing rats: behavioral, electrographic histological and electrophysiological studies. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1999; 116:59-68. [PMID: 10446347 DOI: 10.1016/s0165-3806(99)00075-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Status epilepticus and repeated seizures have age-dependent morphological and neurophysiological alterations in the hippocampus. In the present study, effects of flurothyl-induced status epilepticus were examined in awake and free moving immature (2 weeks old) and adult rats. Without exception, adult rats died of respiratory arrest before the onset of status epilepticus. We were unable to find a concentration of flurothyl that produced status epilepticus and a low mortality in adult rats. In contrast, immature rats survived flurothyl status epilepticus for up to 60 min with a very low mortality. In rat pups, behavioral manifestations correlated with electrographic seizures in both the cortex and hippocampus. Neuropathological damage (cell loss, pyknotic cells or gliosis) was not observed in the immature hippocampus, thalamus, amygdala, substantia nigra or cortex at 24 h, 2 days or 2 weeks after status epilepticus. In addition, no aberrant mossy fiber reorganization or decrease in cells counts were observed in the hippocampus. Young rats did not show alterations in paired-pulse perforant path inhibition following flurothyl status epilepticus. The present findings are consistent with studies in other seizure models, indicating that immature rats are highly resistant to seizure-induced changes.
Collapse
Affiliation(s)
- E F Sperber
- Department of Neurology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | | | | | |
Collapse
|
8
|
Abstract
Over the past twenty years, several lines of evidence from preclinical and clinical studies has accumulated suggesting that a GABA deficit may be involved in mood disorders, particularly in depression, and that increasing GABAergic neurotransmission may exert an antidepressant effect and perhaps a mood stabilizing effect. Given that GABA has an inhibitory effect on biogenic amine neurotransmitters such as norepinephrine and serotonin and this inhibition may be involved in local circuits and interneurons, it has been suggested that the hypothesis of a GABA deficit in mood disorders does not compete with but complements the well-established hypotheses of alterations in noradrenergic and serotonergic function in mood disorders. In this paper, we systematically reviewed the results from preclinical and clinical studies of GABA function in the pathophysiology of mood disorders and in the mechanism of action of mood stabilizers, antidepressants and electroconvulsive therapy. We also discussed the unifying theory of the neurochemistry of mood disorders, which integrates the GABA hypothesis into the biogenic amine hypotheses, and indicated future directions for research.
Collapse
Affiliation(s)
- I S Shiah
- Department of Psychiatry, The University of British Columbia, Vancouver, Canada
| | | |
Collapse
|
9
|
Velísek L, Velísková J, Moshé SL, Vathy I. Prenatal morphine exposure alters ovarian steroid hormonal regulation of seizure susceptibility. Brain Res 1998; 796:247-56. [PMID: 9689475 DOI: 10.1016/s0006-8993(98)00367-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The present study examined the ovarian hormonal regulation of seizure susceptibility in prenatally morphine- and saline-exposed adult female rats in the flurothyl seizure model in vivo, and in low-magnesium-induced epileptiform activity in brain slices, in vitro. All females were ovariohysterectomized (OVX); some received either estrogen (E) or progesterone (P) replacement, while others were injected with E + P sequentially. In prenatally saline-treated control females, there was an increase in the flurothyl-induced clonic seizure threshold (anticonvulsant effect) in the presence of both hormones (E + P) compared to OVX controls. In morphine-exposed females, there was an increase in the flurothyl-induced clonic seizure threshold after an E injection alone while there was a reduced tonic--clonic seizure threshold in the presence of both hormones (E + P) compared to the hormone treatment-matched group of saline-exposed females. In control females, in low magnesium medium in vitro, the development of two types of epileptiform activity (seizure-like events and status of short discharges) was not affected by the different hormonal conditions. However, prenatal morphine exposure suppressed the development of both types of epileptiform activity in the E-injected females compared to the E-injected, control females. The present data demonstrate that the anticonvulsant effects of P on seizure susceptibility requires the presence of E. Furthermore, prenatal morphine exposure alters ovarian steroid hormone-regulated seizure susceptibility.
Collapse
Affiliation(s)
- L Velísek
- Department of Neurology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | | | | | | |
Collapse
|
10
|
Rowley HL, Marsden CA, Martin KF. Differential effects of phenytoin and sodium valproate on seizure-induced changes in gamma-aminobutyric acid and glutamate release in vivo. Eur J Pharmacol 1995; 294:541-6. [PMID: 8750716 DOI: 10.1016/0014-2999(95)00589-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effects of intraperitoneal administration of the anticonvulsants phenytoin and sodium valproate were compared with ethosuximide on maximal electroshock seizure-related changes in rat hippocampal gamma-aminobutyric acid (GABA) and glutamate release in vivo as measured by microdialysis. There were immediate increases in GABA and glutamate in the 5 min post-ictal period, followed by a sustained reduction in GABA levels. Glutamate levels, however, were subsequently reduced until 20 min post-ictal before gradually increasing above basal. All animals displayed tonic hind-limb extension that was blocked by phenytoin (20 mg/kg) and sodium valproate (400 mg/kg) but not ethosuximide (150 mg/kg). Phenytoin attenuated the immediate post-ictal increase observed in glutamate whilst sodium valproate enhanced GABA release and prevented its secondary post-ictal inhibition. Ethosuximide was without effect on the post-ictal changes. These are the first data to show detailed seizure-induced amino acid changes and the in vivo effects of anticonvulsants on them in the seizure model.
Collapse
Affiliation(s)
- H L Rowley
- Department of Physiology and Pharmacology, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK
| | | | | |
Collapse
|
11
|
Rowley HL, Martin KF, Marsden CA. Decreased GABA release following tonic-clonic seizures is associated with an increase in extracellular glutamate in rat hippocampus in vivo. Neuroscience 1995; 68:415-22. [PMID: 7477952 DOI: 10.1016/0306-4522(95)00159-g] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effects of maximal electroshock, used as a model of generalized seizures, were studied on extracellular GABA and glutamate levels in the ventral hippocampus of the freely-moving rat, using in vivo microdialysis. Following a maximal electroshock there was a rapid decline in GABA levels (46 +/- 5%) in the 20 min immediately after the seizure and levels remained depressed for a further 60 min. However, although there was a transient small decrease (11 +/- 2%) in glutamate levels in the first 20 min post-ictally, there followed a more prolonged, larger increase in the next 40 min. Maximal electroshock, administered in the absence of extracellular calcium, did not change GABA levels, while glutamate levels were again increased (42 +/- 8%) in the 40-80 min after the shock. Local perfusion with nickel (1 mM) to block T-type calcium channels had no effect on basal GABA or glutamate levels but prevented maximal electroshock-induced changes in both amino acids. Experiments were carried out to test the hypothesis that the post-ictal increased glutamate release was due to the decrease in GABA release. Perfusion with the potent GABA re-uptake inhibitor NNC-711, for 60 min prior to administration of maximal electroshock, increased GABA levels (436 +/- 58%) and abolished the seizure-induced decrease. Basal glutamate levels were not affected by perfusion with NNC-711 but subsequent maximal electroshock also failed to affect levels. Local perfusion with the GABAA receptor antagonist bicuculline (1, 10 and 100 microM) had no effect on basal GABA levels but glutamate levels were increased (46 +/- 5%) after perfusion with 100 microM bicuculline.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- H L Rowley
- Department of Physiology and Pharmacology, University of Nottingham Medical School, Queen's Medical Centre, U.K
| | | | | |
Collapse
|
12
|
Ukai M, Miura M, Kameyama T. Effects of human epidermal growth factor on passive avoidance and habituation learning in mice. GENERAL PHARMACOLOGY 1994; 25:1157-62. [PMID: 7875539 DOI: 10.1016/0306-3623(94)90132-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
1. Human epidermal growth factor (hEGF:0.02-2.0 micrograms) did not affect passive avoidance response or habituation learning when given before or immediately after training, or before retention. 2. hEGF (0.02-2.0 micrograms) failed to influence the scopolamine- or electroconvulsive shock-induced shortening of step-down latency in passive avoidance response when given before or immediately after training, or before retention. 3. These results suggest that the acute administration of hEGF does not affect memory processes as indexed by passive avoidance or habituation learning in normal or amnesic mice.
Collapse
Affiliation(s)
- M Ukai
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Japan
| | | | | |
Collapse
|
13
|
Pratt JS, Kang I, Bazan NG, Miller LG. Electroconvulsive shock alters GABAA receptor subunit mRNAs: use of quantitative PCR methodology. Brain Res Bull 1993; 30:691-3. [PMID: 7681357 DOI: 10.1016/0361-9230(93)90101-g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Electroconvulsive shock (ECS) may affect several neurotransmitter systems in brain, including the GABAergic inhibitory system. We used a quantitative PCR-based assay to evaluate mRNAs for five GABAa receptor subunits at 2 to 24 h after ECS. mRNAs for the alpha 1 and beta 2 subunits were significantly increased in cerebellum at 4 and 8 h after ECS, and returned to control levels at 24 h. No changes were observed in alpha 2, beta 3, gamma 1, or gamma 2 subunits, and no changes in any subunit evaluated were observed in cortex or hippocampus. These data corroborate prior results obtained for the alpha 1 subunit using Northern hybridization, and illustrate the utility of the PCR assay in quantitating low-abundance mRNAs.
Collapse
Affiliation(s)
- J S Pratt
- Tufts University School of Medicine, Boston, MA 02111
| | | | | | | |
Collapse
|
14
|
Abstract
In brain slices the mechanisms of release of GABA have been extensively studied, but those of taurine markedly less. The knowledge acquired from studies on GABA is, nevertheless, still fragmentary, not to speak of that obtained from the few studies on taurine, and firm conclusions are difficult, even impossible, to draw. This is mainly due to methodological matters, such as the diversity and pitfalls of the techniques applied. Brain slices are relatively easy to prepare and they represent a preparation that may most closely reflect relations prevailing in vivo, since the tissue structure and cellular integrity are largely preserved. In our opinion the most recommendable method at present is to superfuse freely floating agitated slices in continuously oxygenated medium. Taurine is metabolically rather inert in the brain, whereas the metabolism of GABA must be taken into account in all release studies. The use of inhibitors of GABA catabolism is discouraged, however, since a block in GABA metabolism may distort relations between different releasable pools of GABA in tissue. It is not known for sure how well, and homogeneously, incubation of slices with radioactive taurine labels the releasable pools but at least in the case of GABA there may prevail differences in the behavior of labeled and endogenous GABA. It is suggested therefore that the results obtained with radioactive GABA or taurine should be frequently checked and confirmed by analyzing the release of respective endogenous compounds. The spontaneous efflux of both GABA and taurine from brain slices is very slow. The magnitude of stimulation of GABA release by homoexchange is greater than that of taurine under the same experimental conditions. However, the release of both amino acids is generally enhanced by a great number of structural analogs, the most potent being those which are simultaneously the most potent inhibitors of uptake. This may result in part from inhibition of reuptake of amino acid molecules released from slices but the findings may also signify that the efflux of GABA and taurine is at least partially mediated by the membrane carriers operating in an outward direction. It is thus advisable not to interpret that stimulation of release in the presence of uptake inhibitors solely results from the block of reuptake of exocytotically released molecules, since changes in the carrier-mediated transport are also likely to occur upon stimulation. The electrical and K+ stimulation evoke the release of both GABA and taurine. The evoked release of GABA is several-fold greater than that of taurine in slices from the adult brain.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- P Saransaari
- Tampere Brain Research Center, Department of Biomedical Sciences, University of Tampere, Finland
| | | |
Collapse
|
15
|
Green AR, Cross AJ, Snape MF, De Souza RJ. The immediate consequences of middle cerebral artery occlusion on GABA synthesis in mouse cortex and cerebellum. Neurosci Lett 1992; 138:141-4. [PMID: 1407654 DOI: 10.1016/0304-3940(92)90491-o] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effect on gamma-aminobutyric acid (GABA) synthesis of focal ischaemia in the right cortex of the mouse was investigated by performing a right middle cerebral artery (MCA) occlusion. Synthesis of GABA was determined by measurement of the rate of GABA accumulation in tissue following injection of amino oxyacetic acid (AOAA; 30 mg/kg, i.p.). Five min following the MCA occlusion, the rate of GABA synthesis in the right (ischaemic) cortex was decreased by approximately 70% compared to either the left cortex or the right cortex of untreated controls. The basal GABA concentration was however unaffected. Four hours after the occlusion the rate of GABA synthesis was similar in the right and left cortex. The rate of GABA accumulation in the cerebellum was unchanged at both times after the right MCA occlusion compared with untreated control mice. The data suggest that there is a rapid but short lasting decrease in GABA synthesis following an ischaemic insult and it is suggested that this might be associated with the EEG spiking activity that occurs at this time.
Collapse
Affiliation(s)
- A R Green
- Astra Neuroscience Research Unit, London, UK
| | | | | | | |
Collapse
|
16
|
Baxter CF, Oh CC, Wasterlain CG, Ozaki LK, Baldwin RA. Alterations of GABA metabolism and seizure susceptibility in the substantia nigra of the kindled rat acclimating to changes in osmotic state. Neurochem Res 1991; 16:269-78. [PMID: 1780028 DOI: 10.1007/bf00966090] [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: 12/28/2022]
Abstract
Seizure susceptibility and GABA metabolism were altered in the substantia nigra [SN] of adult male Sprague Dawley rats when these animals were acclimating to an altered plasma osmolality. Changes in GABA metabolism were measured in vivo in SN of the freely moving rat. Suitable precautions were taken to avoid any post-mortem flux of glutamate to GABA and to correct for the underestimation of GABA build up in SN due to the finite diffusion rate of gamma-vinyl GABA [GVG] after stereotaxic injection of small amounts into one side of the brain. Control experiments provided evidence that changes in osmolality, within a normal physiological range, did not affect significantly gamma-aminobutyric acid transaminase [GABA-T]. Also kindling via the medial septum [MS], in the absence of electrical stimulation did not alter GABA metabolism in SN, thus providing a stable baseline for studies of osmotic effects. Hyperosmolality was associated with a rise in seizure thresholds, with a marked reduction of the rate of GABA synthesis in SN, and with a substantial increase in turnover time of the GABA pool. Hypoosmolality, of a degree known to be associated with mild cerebral edema and swelling localized to astrocytes, markedly reduced seizure threshold, and reduced GABA pool size in SN, but did not alter the rate of GABA synthesis significantly. These results demonstrate by new and independent means the relationship between GABA metabolism in the SN and seizure susceptibility in vivo.
Collapse
Affiliation(s)
- C F Baxter
- Neurochemistry Laboratory V.A. Medical Center, Sepulveda, California 91343
| | | | | | | | | |
Collapse
|
17
|
Ex vivo release of GABA from tetanus toxin-induced chronic epileptic foci decreased during the active seizure phase. Neurochem Int 1991; 18:373-9. [DOI: 10.1016/0197-0186(91)90169-e] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/1990] [Accepted: 08/28/1990] [Indexed: 11/22/2022]
|
18
|
Glue P, Costello MJ, Pert A, Mele A, Nutt DJ. Regional neurotransmitter responses after acute and chronic electroconvulsive shock. Psychopharmacology (Berl) 1990; 100:60-5. [PMID: 1688661 DOI: 10.1007/bf02245791] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Regional neurotransmitter changes after acute and chronic electroconvulsive shock (ECS) were studied using the technique of repeated microdialysis. Microdialysis was carried out on alternate sides of the brains of anaesthetised rats before and during the first and the eighth ECS or sham (control) treatments. Extracellular fluid release of monoamines and their metabolites was measured in the frontal cortex, striatum and nucleus accumbens using HPLC with electrochemical detection. The first ECS produced selective regional responses, shown by increased concentrations of noradrenaline (NA) and dopamine (DA) in frontal cortex, by unchanged DA content in striatum, and by a small rise in NA and a fall in DA concentrations in nucleus accumbens. Concentrations of metabolites increased after ECS in all regions studied, and for homovanillic acid and dihydroxyphenylacetic acid, the temporal pattern of these changes did not resemble that of DA. Comparison of neurotransmitter responses as per cent of baseline release after the first and eighth ECS treatments showed they were identical. Basal release of monoamines and metabolites before the first ECS or sham treatment was similar in all regions studied. Prior to the eighth treatment, basal release of NA in the frontal cortex and DA in the striatum was elevated in the ECS-treated animals, while basal release of NA in the nucleus accumbens was reduced in both ECS- and sham-treated animals. These data suggest that acute and chronic ECS have different and region-specific effects on neurotransmitter release, although the overall pattern of these responses is not changed by chronic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- P Glue
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD 20892
| | | | | | | | | |
Collapse
|
19
|
Kulkarni SK, Ticku MK. Binding pattern of [35S]t-butylbicyclophosphorothionate is not altered following electroconvulsive shock treatment in rats. Brain Res Bull 1989; 22:575-7. [PMID: 2540888 DOI: 10.1016/0361-9230(89)90115-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Single or repeated electroconvulsive shock (ECS) treatment-induced changes in [35S]t-butylbicyclophosphorothionate [( 35S]TBPS) binding patterns in specific regions, i.e., cerebral cortex, cerebellum, hippocampus, and striatum of rat brain were investigated. Specific [35S]TBPS binding in these brain regions was not altered following a single or repeated administration of ECS, nor was the inhibition of [35S]TBPS binding to GABA affected. These observations tend to suggest that the picrotoxin-site on the GABA receptor complex may not be directly involved in electroconvulsive shock.
Collapse
Affiliation(s)
- S K Kulkarni
- Department of Pharmacology, University of Texas Health Science Center, San Antonio 72884-7764
| | | |
Collapse
|
20
|
Green AR, Heal DJ, Vincent ND. The effects of single and repeated electroconvulsive shock administration on the release of 5-hydroxytryptamine and noradrenaline from cortical slices of rat brain. Br J Pharmacol 1987; 92:25-30. [PMID: 3664089 PMCID: PMC1853631 DOI: 10.1111/j.1476-5381.1987.tb11291.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1 A method is described of measuring the K+-evoked release of endogenous 5-hydroxytryptamine (5-HT) and noradrenaline (NA) from slices prepared from rat cortex. 2 There was no difference in either the spontaneous (basal) or K+-evoked release of 5-HT or NA from cortical slices prepared from handled animals and those given a single electroconvulsive shock (ECS) either 30 min or 24 h earlier. 3 In chronic studies, rats were either handled or given an ECS 5 times over 10 days and cortical slices prepared. There was no difference in 5-HT or NA release between the groups 30 min after the last treatment other than a modest attentuation of spontaneous NA release following ECS treatment. However 24 h after the last treatment K+-evoked release (above basal release) of 5-HT and NA was inhibited by 84% and 48%, respectively. 4 These data demonstrate that following a single ECS, normal 5-HT and NA release is seen at a time when GABA release is markedly inhibited. After repeated ECS the release of both monoamines was markedly inhibited. These 5-HT changes may be involved in the enhanced 5-HT-receptor function seen after repeated ECS.
Collapse
Affiliation(s)
- A R Green
- MRC Clinical Pharmacology Unit, Radcliffe Infirmary, Oxford
| | | | | |
Collapse
|
21
|
Green AR, Minchin MC, Vincent ND. Inhibition of GABA release from slices prepared from several brain regions of rats at various times following a convulsion. Br J Pharmacol 1987; 92:13-8. [PMID: 3664084 PMCID: PMC1853605 DOI: 10.1111/j.1476-5381.1987.tb11289.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1 A method is described for the measurement of the K+-evoked release of endogenous gamma-aminobutyric acid (GABA) from slices of rat cortex, hippocampus and striatum. 2 In tissue prepared 30 min following an electroconvulsive shock, K+-evoked GABA release (above basal release) was inhibited by 45% in cortex, 50% in hippocampus and 75% in striatum. A similar inhibition of release was observed with slices prepared from rats in which a convulsion had been induced by flurothyl. There was no change in spontaneous (basal) release following either procedure. 3 An inhibition of K+-evoked endogenous GABA release was also seen in tissue prepared 4 min postictally but not 2 h after the seizure. 4 No difference was observed in the release of [3H]-GABA from preloaded cortical slices prepared from rats given a single electroconvulsive shock. 5 It is proposed that a convulsion results in an inhibition of GABA release and that this inhibition may in turn inhibit GABA synthesis as described in the preceding paper. 6 It is also proposed that changes in the endogenous releasable pool of GABA may not be detected by preloading slices with [3H]-GABA.
Collapse
Affiliation(s)
- A R Green
- MRC Clinical Pharmacology Unit, Radcliffe Infirmary, Oxford
| | | | | |
Collapse
|
22
|
Green AR, Metz A, Minchin MC, Vincent ND. Inhibition of the rate of GABA synthesis in regions of rat brain following a convulsion. Br J Pharmacol 1987; 92:5-11. [PMID: 3664092 PMCID: PMC1853628 DOI: 10.1111/j.1476-5381.1987.tb11288.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1 The rate of synthesis of gamma-aminobutyric acid (GABA) in the cortex, hippocampus and striatum of rat brain was assessed by measuring the linear rate of accumulation of GABA following injection of amino-oxyacetic acid (AOAA). 2 Five min after a single electrically induced seizure there was a rise in GABA content in these brain regions and an almost total inhibition of the rate of synthesis. 3 Five min after seizure induced by the inhalant convulsant flurothyl there was no rise in GABA content in these brain regions but a similar marked degree of inhibition of GABA synthesis. 4 Two hours after the convulsion the rate of GABA synthesis had returned to control values in all three brain regions. 5 A single convulsion did not alter the glutamic acid decarboxylase activity in these brain regions either in the absence or presence of added co-factor (pyridoxal phosphate). 6 Evidence for an inhibition of GABA release following a convulsion which may be associated with the inhibition of GABA synthesis is presented in the following paper.
Collapse
Affiliation(s)
- A R Green
- MRC Clinical Pharmacology Unit, Radcliffe Infirmary, Oxford
| | | | | | | |
Collapse
|
23
|
Green AR, Vincent ND. The effect of repeated electroconvulsive shock on GABA synthesis and release in regions of rat brain. Br J Pharmacol 1987; 92:19-24. [PMID: 3664087 PMCID: PMC1853615 DOI: 10.1111/j.1476-5381.1987.tb11290.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1 The release of endogenous gamma-aminobutyric acid (GABA) from slices of rat cortex, hippocampus and striatum prepared both 30 min and 24 h after the last of a series of electroconvulsive shocks (5 seizures given spread out over 10 days) has been investigated. 2 No change in spontaneous (basal) release was observed. However, 30 min after the last convulsion, K+-evoked GABA release above basal release was inhibited in both hippocampus (20%) and striatum (33%) but not in the cortex. Release was still inhibited in striatum (22%) 24 h after the last seizure. 3 In confirmation of an earlier report, chronic electroconvulsive shock was found to increase basal GABA content in striatum and inhibit synthesis by 34%. The synthesis rate was also inhibited in the hippocampus (44%) but not in the cortex. 4 Glutamic acid decarboxylase activity was unchanged in all regions after repeated electroconvulsive shock treatment. 5 It is proposed that repeated electroconvulsive shocks lead to a substantial inhibition of release in the striatum and hippocampus and a long-term inhibition of GABA synthesis in these regions. Such changes may be associated with the altered monoamine biochemistry and function observed after repeated electroconvulsive shock and with the mechanism of the antidepressant action of electroconvulsive therapy.
Collapse
Affiliation(s)
- A R Green
- MRC Clinical Pharmacology Unit, Radcliffe Infirmary, Oxford
| | | |
Collapse
|