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Interneuron dysfunction in epilepsy: An experimental approach using immature brain insults to induce neuronal migration disorders. Epilepsy Res 2019; 156:106185. [DOI: 10.1016/j.eplepsyres.2019.106185] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 07/13/2019] [Accepted: 08/02/2019] [Indexed: 01/16/2023]
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2
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Takano T, Matsui K. Increased expression of GAP43 in interneurons in a rat model of experimental polymicrogyria. J Child Neurol 2015; 30:716-28. [PMID: 25061039 DOI: 10.1177/0883073814541476] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 06/01/2014] [Indexed: 12/15/2022]
Abstract
To investigate seizure susceptibility in polymicrogyria, the seizure threshold and growth-associated protein GAP43 expression were analyzed in a rat experimental model of polymicrogyria induced by intracerebral injection of ibotenate. A total of 72 neonates from 9 pregnant rats were used. Intraperitoneal pentylenetetrazole injection did not induce any seizure activity in the control rats, although it elicited seizures of variable severity in the polymicrogyria rats. Fluoro-Jade B-positive degenerating interneurons were found in the polymicrogyria brains; however, no such neurons were detected in the control brains. In the polymicrogyria rats, the GAP43 expression was significantly and widely distributed in the brain, and the percentage of parvalbumin-positive interneurons in the GAP43-positive cells was significantly higher than that observed in the nonphosphorylated neurofilament-positive pyramidal cells. We conclude that the relatively selective vulnerability of inhibitory interneurons constitutes the basis for the decreased seizure threshold observed in this model of polymicrogyria.
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Affiliation(s)
- Tomoyuki Takano
- Department of Pediatrics, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Japan
| | - Katsuyuki Matsui
- Department of Pediatrics, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Japan
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Oghlakian RO, Tilelli CQ, Hiremath GK, Alexopoulos AV, Najm IM. Single injection of a low dose of pentylenetetrazole leads to epileptogenesis in an animal model of cortical dysplasia. Epilepsia 2009; 50:801-10. [DOI: 10.1111/j.1528-1167.2008.01815.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bazyan AS, Mel'nik VI, Bikbulatova LS, Karpova MN. The pentylenetetrazole allosteric component of the GABAA receptor plasticity. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2002; 386:400-3. [PMID: 12469399 DOI: 10.1023/a:1020745730228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- A S Bazyan
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, ul. Butlerova 5a, Moscow, Russia
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Koryntová H, Kubová H, Tutka P, Mares P. Changes of cortical epileptic afterdischarges under the influence of convulsant drugs. Brain Res Bull 2002; 58:49-54. [PMID: 12121812 DOI: 10.1016/s0361-9230(02)00759-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Convulsant drugs picrotoxin (0.5 and/or 1 mg/kg, intraperitoneal (i.p.)) and pentylenetetrazol (10 and/or 20 mg/kg, i.p.) were used to compromise GABAergic inhibition, caffeine (75 and/or 150 mg/kg, i.p.) to antagonize adenosinergic system to study the role of inhibition in cortical epileptic afterdischarges. Rats with implanted cortical stimulation and registration electrodes were stimulated four times at 10-min intervals, drugs were injected between the first and second stimulation. Four different phenomena were evaluated: movements directly bound to stimulation were intensified by all three drugs, i.e., excitability of the cerebral cortex was increased. Incidence of two types of afterdischarges (spike-and-wave rhythm and "limbic" type) was not changed by any drug, i.e., the transition of epileptic activity into limbic structures was not increased. Afterdischarges were most efficiently prolonged by caffeine, i.e., caffeine probably interferes with mechanism(s) arresting cortical afterdischarges. The intensity of clonic seizures accompanying spike-and-wave afterdischarges, i.e., spread of epileptic activity into the motor system was only transiently increased by picrotoxin, the effects of caffeine did not reach the level of statistical significance. Our results indicate various mechanisms and diverse role of the two inhibitory systems in generation of evaluated phenomena.
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Affiliation(s)
- H Koryntová
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Gatch MB, Wallis CJ, Lal H. Effects of calcium channel blockers on pentylenetetrazol drug discrimination in rats. Alcohol 2001; 23:141-7. [PMID: 11435024 DOI: 10.1016/s0741-8329(01)00123-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effects of the dihydropyridine L-type calcium channel blockers nitrendipine and nimodipine on the pentylenetetrazol (PTZ) drug discrimination, an operant model of anxiety, were investigated. Male Long-Evans rats were trained to discriminate PTZ (16 mg/kg, i.p.) from saline. Both nitrendipine (5.0-25 mg/kg, i.p.) and nimodipine (5.0-25 mg/kg, i.p.) partially substituted for the PTZ discriminative stimulus. However, pretreatment with nitrendipine (25 mg/kg, i.p.) or nimodipine (25 mg/kg, i.p.) produced no change in the PTZ dose-effect function. Rats were given a nutritionally balanced liquid diet containing 6.5% ethanol for 10 days. Rats selected the PTZ drug lever during withdrawal. Subchronic coadministration of nitrendipine (1.25-5.0 mg/kg, i.p., b.i.d.) with ethanol failed to dose-dependently reduce PTZ-lever responding, but it did reverse withdrawal signs. Acute administration of nitrendipine (5, 10, and 20 mg/kg, i.p.) produced marked suppression of lever responding, but it failed to significantly reduce levels of PTZ-lever responding. Although calcium channel blockers reduce signs of ethanol withdrawal, they also markedly reduce rates of behavior and produce no clear effects on anxiety-like behaviors induced by ethanol withdrawal.
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Affiliation(s)
- M B Gatch
- Department of Pharmacology, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
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Bazyan AS, Zhulin VV, Karpova MN, Klishina NY, Glebov RN. Long-term reduction of benzodiazepine receptor density in the rat cerebellum by acute seizures and kindling and its recovery 6 months later by a pentylenetetrazole challenge. Brain Res 2001; 888:212-220. [PMID: 11150477 DOI: 10.1016/s0006-8993(00)03045-6] [Citation(s) in RCA: 22] [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
Seizures induced by an acute pentylenetetrazole (50 mg/kg) injection were accompanied by a long-term (at 1-48 h, but not on day 7) decrease in the density (B(max)) of [3H]-diazepam binding to benzodiazepine receptors in rat cerebellar cortex with no change in affinity (K(d)). Kindling for 24 days by daily administrations of pentylenetetrazole (20 mg/kg) led to the same decrease in benzodiazepine receptor density (at 1-48 h, but not on day 7) as that observed after a single dose of pentylenetetrazole (50 mg/kg). This suggests a common mechanism for both acute and kindling-induced seizures, dependent on the long-term receptor changes. The increased susceptibility to seizures persisted for 6 months after the termination of kindling, with BDZ receptor density in cerebellar cortex reduced almost by half. In age-matched controls, an acute dose of PTZ (30 mg/kg) induced seizures and decrease in both B(max) and K(d) of [3H]-diazepam binding. In kindled rats, at 6 months post-kindling, the same dose of PTZ (30 mg/kg) restored the benzodiazepine receptor density to the level found 6 months before, at the time of termination of kindling. Also, the severity of seizures was enhanced in the kindled rats. The results are discussed in terms of a balance of inhibitory and excitatory processes, in which the reduced BDZ receptor density at 6 months post-kindling may represent a compensatory reaction to outbalance some alterations in excitatory systems that have been reported to be induced by kindling.
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Affiliation(s)
- A S Bazyan
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Butlerov St. 5A, GSP-7, 117865, Moscow, Russia.
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Abstract
This study investigated the ability of ritanserin, a 5-HT2 antagonist, to modify ethanol withdrawal (EW) symptoms in two animal models of anxiety: the elevated plus-maze (EPM) and the pentylenetetrazol (PTZ) discrimination assay. Long-Evans hooded rats were given a nutritionally balanced liquid diet containing 4.5% ethanol for 10 days. Twelve hours after removal of the ethanol diet, rats were tested in the EPM. A significant reduction in the open-arm activity and the number of total arm entries was observed, which is indicative of EW. Acute ritanserin (0.16-0.64 mg/kg, i.p., 60 min) had no effect on EW-induced anxiety-like behavior on the EPM. Ritanserin (0.08-0.64 mg/kg, i.p., b.i.d. 12 h) administered concurrently with the last 5 days of ethanol diet produced an increase in the time spent on the open arms of the EPM and reversed the EW-induced reduction in total arm entries. Rats trained to discriminate between saline and PTZ (an anxiogenic drug), selected the PTZ lever during EW. Chronic ritanserin (0.32 mg/kg, i.p., b.i.d. ) did not block PTZ lever responding during EW. On the rotorod, ritanserin (0.32 mg/kg, i.p.) increased the motor incoordination induced by ethanol. In conclusion, coadministration of ritanserin with ethanol prevented the development of EW-induced anxiety as measured by the EPM, but not in the PTZ drug discrimination.
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Affiliation(s)
- M B Gatch
- Department of Pharmacology, University of North Texas Health Science Center, Fort Worth 76107, USA.
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Maksay G, Molnár P, Gruber L. Common modes of action of gamma-butyrolactones and pentylenetetrazol on the GABAA receptor-ionophore complex. Eur J Pharmacol 1994; 288:61-8. [PMID: 7705469 DOI: 10.1016/0922-4106(94)90010-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of pentylenetetrazol and bicyclic gamma-butyrolactones of similar stereostructures were studied on the convulsant and benzodiazepine binding sites and chloride ionophore activity of the gamma-aminobutyric acid (GABAA) receptor-complex. Bicyclic gamma-butyrolactones displayed millimolar IC50 values and low stereoselectivities on [35S]t-butylbicyclophosphorothionate (TBPS) binding to the convulsant sites in synaptosomal membranes of rat forebrains. Ring saturation of bicyclic gamma-butyrolactones decreased their IC50 values by one order of magnitude. The IC50 values of saturated bicyclic gamma-butyrolactones and pentylenetetrazol were increased by GABA versus its antagonist R 5135 (3 alpha-hydroxy-16-imino-5 beta,17-aza-androstan-11-one). A bicyclic gamma-butyrolactone and pentylenetetrazol accelerated the dissociation of [35S]TBPS, displaced [3H]flumazenil binding in two phases and blocked the muscimol-elicited chloride currents in patch-clamped cortical neurones in culture in a similar manner. These similar effects on binding and ionophore function support their common modes of action on the GABAA receptor-ionophore complex.
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Affiliation(s)
- G Maksay
- Department of Molecular Pharmacology, Hungarian Academy of Sciences, Budapest
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Karpova MN, Germane SK, Tsebers G, Pankov OY, Klusha VE, Duburs GY, Bisenieks EA. Anticonvulsive activity of glutapyrone, a new type of derivative of amino acid-containing 1,4-dihydropyridines. Bull Exp Biol Med 1993. [DOI: 10.1007/bf00820235] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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12
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Ator NA, Cook JM, Griffiths RR. Drug discrimination in pentylenetetrazol-trained baboons: Generalization to buspirone and ?-carboline-3-carboxylic acid ethyl ester but not lorazepam or pentobarbital. Drug Dev Res 1989. [DOI: 10.1002/ddr.430160219] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Bender AS, Hertz L. Evidence for involvement of the astrocytic benzodiazepine receptor in the mechanism of action of convulsant and anticonvulsant drugs. Life Sci 1988; 43:477-84. [PMID: 2900457 DOI: 10.1016/0024-3205(88)90148-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The anticonvulsant drugs carbamazepine, phenobarbital, trimethadione, valproic acid and ethosuximide at pharmacologically relevant concentrations inhibit [3H]diazepam binding to astrocytes in primary cultures but have much less effect on a corresponding preparation of neurons. Phenytoin as well as pentobarbital (which is not used chronically as an anticonvulsant) are equipotent in the two cell types. The convulsants picrotoxinin and pentylenetetrazol, the convulsant benzodiazepine RO 5-3663 and the two convulsant barbiturates DMBB and CHEB similarly inhibit diazepam binding to astrocytes but have little effect on neurons. On the basis of these findings it is suggested that these convulsants and anticonvulsants owe at least part of their effect to an interaction with the astrocytic benzodiazepine receptor, perhaps by interference with a calcium channel.
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Affiliation(s)
- A S Bender
- Department of Pharmacology, University of Saskatchewan, Saskatoon, Canada
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Dan'ura T, Kurokawa T, Yamashita A, Yanagiuchi H, Ishibashi S. Inhibition of rat brain adenylate cyclase activity by benzodiazepine through the effects on Gi and catalytic proteins. Life Sci 1988; 42:469-75. [PMID: 2828793 DOI: 10.1016/0024-3205(88)90086-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effect of benzodiazepines on adenylate cyclase system was examined in rat brain. Micromolar concentrations of diazepam inhibited the enzyme activity in synaptic membranes in dose- and time-dependent manners. The inhibitory effect of diazepam was more evident on the enzyme activity in the presence of guanylyl-5'-imidodiphosphate (GppNHp) or NaF-AlCl3 than on that in the basal state. In the pertussis toxin-treated membranes, the effect of diazepam in the presence of GppNHp or NaF-AlCl3 was markedly suppressed. In addition, other benzodiazepines, such as medazepam, flurazepam, flunitrazepam, and clonazepam, had similar effects to those of diazepam, whereas Ro15-1788, an antagonist of a high affinity receptor in the central nervous system, had no effect on adenylate cyclase activity and did not antagonize the effect of diazepam. These findings indicate that benzodiazepines inhibit rat brain adenylate cyclase activity through the effects on both a low affinity benzodiazepine receptor coupled with the inhibitory GTP-binding regulatory protein (Gi) and catalytic protein.
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Affiliation(s)
- T Dan'ura
- Department of Physiological Chemistry, Hiroshima University School of Medicine, Japan
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Hantraye P, Brouillet E, Guibert B, Chavoix C, Fukuda H, Prenant C, Crouzel M, Naquet R, Maziere M. Pentylenetetrazol-induced seizure is not mediated by benzodiazepine receptors in vivo. Neuropharmacology 1987; 26:1509-12. [PMID: 2825060 DOI: 10.1016/0028-3908(87)90171-7] [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: 01/02/2023]
Abstract
The selective benzodiazepine antagonist RO 15-1788, labelled with carbon 11 [11C] RO 15-1788, as a specific marker, together with positron emission tomography, allows the in vivo study of benzodiazepine receptors in primates. In addition, when coupled with recordings of electroencephalographic activity, this method offers the feasibility of studying the correlation between occupancy of benzodiazepine receptors and the convulsant action of drugs acting at the benzodiazepine-GABA receptor complex in vivo. The present study showed that convulsant doses of pentylenetetrazol (PTZ) could affect the binding of [11C] RO 15-1788 in vivo in two ways, depending on the doses tested: at concentrations of 20 and 30 mg/kg, pentylenetetrazol increased the binding of [11C] RO 15-1788 whereas larger concentrations displaced the binding of [11C] RO 15-1788. The direct correlation between the occupancy of respective benzodiazepine receptors, afforded by increasing convulsant doses of pentylenetetrazol, revealed that competitive interaction with benzodiazepine receptors was not necessary for pentylenetetrazol to induce the appearance of seizures in vivo.
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Affiliation(s)
- P Hantraye
- Service Hospitalier Frédéric Joliot, C.E.A., Département de Biologie, Orsay, France
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Chweh AY, Ulloque RA, Swinyard EA. Benzodiazepine inhibition of [3H]flunitrazepam binding and caffeine-induced seizures in mice. Eur J Pharmacol 1986; 122:161-5. [PMID: 2872063 DOI: 10.1016/0014-2999(86)90098-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The median inhibitory and anticonvulsant potencies of seven benzodiazepine (BDZ) agonists and one BDZ antagonist (Ro15-1788) were established by two tests: inhibition of [3H]flunitrazepam receptor binding and prevention of caffeine-induced seizures in mice. The effect of Ro15-1788 on the anticonvulsant potency of diazepam against caffeine-induced seizures was also investigated. The [3H]flunitrazepam receptor binding inhibitory potencies (IC50s) of the BDZ agonists correlate well with their anticonvulsant potencies (ED50s) against caffeine-induced seizures (r = 0.831; P greater than 0.01 and less than 0.05). Ro15-1788 and clonazepam are the most potent inhibitors (IC50s: 1.72 and 1.75 nM, respectively), but differ markedly in their ability to obtund caffeine-induced seizures (ED50s: 43.2 and 0.226 mg/kg, respectively). Although both Ro15-1788 and diazepam are effective against caffeine-induced seizures, when used in combination Ro15-1788 antagonizes the anti-caffeine effect of diazepam. These data indicate that Ro15-1788 is a BDZ partial agonist with low efficacy as well as a potent antagonist.
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Nitsch C, Goping G, Klatzo I. Pathophysiological aspects of blood-brain barrier permeability in epileptic seizures. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1986; 203:175-89. [PMID: 3788703 DOI: 10.1007/978-1-4684-7971-3_13] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Blood-brain barrier (BBB) permeability to macromolecules was assessed during seizures induced by pentylenetetrazole, bicuculline, methoxypyridoxine, methionine sulfoximine, and kainic acid. It was observed that each convulsant induced a specific pattern of regional BBB opening. This was, however, only the case when systemic blood pressure (BP) rose with seizure onset. The analysis of regional cerebral blood flow revealed that a high increase in flow in rabbits with BP rise is related to the normal flow at rest in the single brain region, but not to BBB permeability. In rabbits without BP increase, regional flow increase was low but well modulated and is possibly a better indicator for neuronal activity. The ultrastructural analysis showed that macromolecular transport over the cerebrovascular endothelium is by pinocytosis, an neurotransmitter controlled process. It is suggested that seizure-induced regional BBB opening is determined by two factors: release of neurotransmitters due to the process of auto-regulation during peripheral pressure increase, and change in local neurotransmitter milieu due to the action of the convulsant and/or the seizure activity.
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Manchon M, Kopp N, Bobillier P, Miachon S. Autoradiographic and quantitative study of benzodiazepine-binding sites in human hippocampus. Neurosci Lett 1985; 62:25-30. [PMID: 2999653 DOI: 10.1016/0304-3940(85)90279-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Benzodiazepine-binding sites were studied on frozen sections of 5 human hippocampi, using autoradiographic and biochemical techniques. The affinity, density, distribution and heterogeneity (two types) of sites were investigated using [3H]flunitrazepam as a ligand, clonazepam or C1 218872 as displacing agents. The autoradiographic images evidence a differential distribution of the binding sites in the histologic layers of the hippocampus. Subtypes I and II coexist in the same proportion in the three layers exhibiting the highest densities of binding sites (stratum granulosum and pyramidale, deep layer of stratum radiatum). The Kd, Bmax and Ki values found here are analogous to those described in animal studies, but the anatomical distribution of the sites in human hippocampus seems to differ slightly from that previously described in that of the rat.
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Kryzhanovskii GN, Shandra AA. Effect of diazepam, carbamazepine, sodium valproate, and their combinations with vitamins on epileptic activity. Bull Exp Biol Med 1985. [DOI: 10.1007/bf00836145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Coleman JC, Shenoy AK, Chweh AY, Swinyard EA. An analysis of the in vivo interactions between chemical convulsants and anticonvulsants. Life Sci 1985; 37:749-55. [PMID: 3927098 DOI: 10.1016/0024-3205(85)90545-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The interactions between pentylenetetrazol (PTZ), picrotoxin (PIC), or bicuculline (BIC) and diazepam, phenobarbital, or valproate were subjected to Schild plot analysis. Log dose-probit response curves for minimal clonic seizures were determined for three chemical convulsants in the absence and in the presence of various concentrations of three anticonvulsants. The calculated median convulsant doses were subjected to Schild plot analysis and the pA2 values determined. A comparison of the pA2 values for the various convulsant/anticonvulsant combinations suggested the following conclusions: (i) the sequence of events leading to minimal clonic seizures evoked by PTZ or PIC involves a common receptor, (ii) BIC acts through a different receptor, and (iii) Schild plot analysis of the antagonism between convulsant and anticonvulsant is in agreement with their antagonism in vitro studies. Thus, Schild plot analysis can be useful in the evaluation of anticonvulsant activity in vivo and may offer some insight into the potential clinical usefulness of anticonvulsant substances.
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Chweh AY, Ulloque RA, Swinyard EA, Wolf HH. Effect of picrotoxinin on benzodiazepine receptor binding. Neurochem Res 1985; 10:871-7. [PMID: 2995853 DOI: 10.1007/bf00964624] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of picrotoxinin on [3H]flunitrazepam binding to benzodiazepine receptors was investigated. In mouse forebrain membranes, picrotoxinin inhibited basal, GABA- and pentobarbital-stimulated [3H]flunitrazepam binding; this inhibitory activity was temperature- and chloride ion-dependent. Scatchard analysis of the data indicates that picrotoxinin decreases the number of binding sites without altering binding affinity. In cerebellar membranes, picrotoxinin did not alter [3H]flunitrazepam receptor binding.
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Chweh AY, Swinyard EA, Wolf HH. gamma-Aminobutyric acid: temperature dependence in benzodiazepine receptor binding. J Neurochem 1985; 45:240-3. [PMID: 2860208 DOI: 10.1111/j.1471-4159.1985.tb05499.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of muscimol and/or incubation temperature on the inhibition of [3H]flunitrazepam receptor binding by benzodiazepine receptor ligands were investigated. At 0 degree C muscimol decreased the Ki values for some ligands as displacers of [3H]flunitrazepam binding to brain-specific sites while increasing or having no effect on the Ki values for other ligands. The Ki values for some ligands are higher at 37 degrees C than at 0 degree C but are reduced by muscimol at both 0 degrees and 37 degrees C. In contrast, the ligands whose Ki values are increased by muscimol either decreased or did not alter the Ki values at 37 degrees C as compared to those at 0 degree C. Incubation of membranes at 37 degrees C for 30 min accelerated gamma-aminobutyric acid (GABA) release by 221% over that at 0 degree C. These results indicate that changes in incubation temperature alter benzodiazepine receptor affinity for ligands via GABA.
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Abstract
Progabide (50 mg/kg, i.p.), a GABA receptor agonist, significantly decreases the median minimal neurotoxic dose (TD50) of clobazam, chlordiazepoxide, and diazepam; the receptor binding of these substances is highly enhanced by muscimol. Progabide has no significant effect on the TD50 of clonazepam and triazolam; the receptor bindings of these substances is either only slightly enhanced or not altered by muscimol. Progabide also significantly decreases the median antimaximal electroshock dose (MES ED50) of all the benzodiazepines tested. However, progabide has no effect on the median antipentylenetetrazol dose (PTZ ED50) of the benzodiazepines. Likewise, THIP (2.5 mg/kg, i.p.) significantly decreases the TD50 of chlordiazepoxide but not that of triazolam. THIP significantly decreases the MES ED50 of chlordiazepoxide and triazolam but has no effect on the PTZ ED50 of these two substances. The above data suggest that benzodiazepine receptors linked to GABA receptors contribute to the minimal neurotoxicity and anti-MES activity but not to the anti-PTZ activity of benzodiazepines.
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Maksay G, Ticku MK. Dissociation of [35S]t-butylbicyclophosphorothionate binding differentiates convulsant and depressant drugs that modulate GABAergic transmission. J Neurochem 1985; 44:480-6. [PMID: 2981283 DOI: 10.1111/j.1471-4159.1985.tb05439.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The dissociation of [35S]t-butylbicyclophosphorothionate ([35S]TBPT) from binding sites on membranes from rat cerebral cortex, after addition of saturating concentrations of convulsant and depressant drugs, was studied. The addition of unlabeled TBPT, picrotoxinin, or pentamethylenetetrazol resulted in dissociation patterns that were monophasic and not distinguishable, suggesting that these convulsants bind competitively to the same (convulsant) sites. In contrast, gamma-aminobutyric acid (GABA) greatly facilitated [35S]TBPT dissociation by binding allosterically to the GABA recognition site of the receptor-ionophore complex. TBPT dissociation was similarly accelerated by the depressants etazolate, (+)-etomidate, and barbiturates. The convulsant and depressant S(+) and R(-) stereoisomers of N-methyl-5-phenyl-5-propyl-barbituric acid displayed large stereoselectivity in the acceleration of TBPT dissociation. These results suggest that depressants bind to sites different from the convulsant sites of the allosteric GABA receptor complex, or the binding of depressants to the same population of sites elicits negative cooperativity and dissociates the convulsants.
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Ibba M, Mennini T, Testa R. Enhancement of diazepam activities induced by denzimol in mice. PHARMACOLOGICAL RESEARCH COMMUNICATIONS 1985; 17:95-103. [PMID: 2984708 DOI: 10.1016/0031-6989(85)90055-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Denzimol, a new anticonvulsant drug, enhances the depressant and antimetrazol activities of diazepam in mice, in a dose and time-dependent fashion. The depressant and anticonvulsant activities of phenobarbital were not affected by Denzimol. It is suggested that Denzimol induces an increase in the number of the benzodiazepine receptors, and that such increase might be responsible for the enhancement of the diazepam's activities.
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Abstract
We are selectively breeding mice prone (WSP) and resistant (WSR) to ethanol withdrawal seizures assessed by handling induced convulsions (HIC). The possibility that differences between the lines in HIC scores are a result of differences in general CNS excitability not specific to ethanol withdrawal was examined. Using treatments which produce generalized seizures (electroconvulsive shock, strychnine, and flurothyl) and gamma amino-butyric acid (GABA) antagonists (picrotoxin, bicuculline, and pentylentetrazol), the ED50 for seizures was determined in the selected lines. In addition, the sensitivity of WSP and WSR mice to the anticonvulsant actions of ethanol against each treatment was determined. Neither the convulsant amperage 50 (CA50) for ECS nor the ED50 for any drug treatment differed for the selected lines. When ethanol (1.5 g/kg) was administered prior to ECS, there was a dramatic differential suppression of ECS in the lines: the CA50 of WSR mice was elevated 5-fold, whereas the CA50 of WSP mice increased only two fold. Ethanol pretreatment also elevated the ED50 for strychnine and flurothyl in WSR mice significantly more than WSP mice, but the line difference was smaller than for the anticonvulsant effect against ECS. The ED50s for the GABA antagonists were not different between the WSR and WSP lines after ethanol pretreatment. We conclude that genetic selection is producing lines of mice that differ specifically in the degree of seizure severity caused by withdrawal from ethanol physical dependence and not in generalized CNS excitability. An increased sensitivity to the anticonvulsant effects of ethanol against some convulsant treatments has appeared as a correlated response to selection in the WSR line.
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Prado de Carvalho L, Grecksch G, Cavalheiro EA, Dodd RH, Chapouthier G, Rossier J. Characterization of convulsions induced by methyl beta-carboline-3-carboxylate in mice. Eur J Pharmacol 1984; 103:287-93. [PMID: 6436041 DOI: 10.1016/0014-2999(84)90489-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The convulsive properties of methyl beta-carboline-3-carboxylate (beta-CCM) were evaluated in mice. When injected subcutaneously at a dose of 10 mg/kg beta-CCM induced convulsions in 75% of the mice with a median latency of 2.12 +/- 0.25 min. The CD50 was determined to be about 5 mg/kg. Electroencephalographic recordings showed that convulsions were brief (10 s), of cortical origin and propagating rapidly to the hippocampus. EEG alterations induced by low doses of beta-CCM lasted up to 1 h. The convulsive effect of beta-CCM was compared to that of PTZ. PTZ-induced convulsions occurred with a longer latency (9.26 +/- 1.33 min). beta-CCM and PTZ could act synergistically when injected in non-convulsive doses. When beta-CCM was injected 2-30 min before pentylenetetrazol (PTZ) there was a clear potentiation of the convulsive effect of PTZ. The convulsions induced by beta-CCM were blocked by diazepam (DZ) and by Ro 15-1788. In addition, beta-CCM reversed the sedative effect of a high dose of DZ for more than 30 min. Our results confirm that beta-CCM acts through the BZ receptor and indicate that the effects induced by a single dose of beta-CCM last more than 30 min.
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Abstract
The objective of this investigation was to determine whether the effects of muscimol on benzodiazepine receptor binding relate to the hypnotic activity of nine benzodiazepines (clonazepam, triazolam, diazepam, flurazepam, nitrazepam, oxazepam, temazepam, clobazam, and chlordiazepoxide) and CL 218,872. There was no correlation between the basal receptor binding affinities of the drugs tested and their hypnotic potencies, whereas the benzodiazepine receptor agonists whose receptor bindings are strongly modulated by muscimol possess potent hypnotic activity. These results indicate that benzodiazepine receptors that couple to GABA receptors are involved in the hypnotic activity of the benzodiazepines.
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