Epileptic focus in the forebrain of the turtle

Volanschi, D; Servít, Z

doi:10.1016/0014-4886(69)90011-9

Cited by 12 publications

(5 citation statements)

References 7 publications

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“…Cortical focal discharges started after a mean latency of 4.6 min compared to 14.5 min in intact animals (Volanschi and Servit 1969a, P = 0.01). The interval between discharges was 5-20 sec compared to the normal of 2 1-30 sec.…”

Section: Influence Of Intrathalamic Penicillin On the Development Of mentioning

confidence: 87%

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Experimental Thalamic Focus and Thalamocortical Epileptogenic Mechanisms in the Brain of Turtle

Servít¹,

Strejcková²

1973

Epilepsia

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SUMMARY An experimental model of the thalamocortical (centrencephalic) component of seizure susceptibility was induced in 29 turtles. An, epileptic focus was elicited in thalamus by electrophoretic administration of penicillin. Thalamic discharges were projected to ipsilateral, sometimes also contralateral, sensory cortex of the forebrain. The thalamic focus increased the duration and frequency of cortical spindles and enhanced the activity of the cortical penicillin focus by shortening the latency of its origin and the time between discharges. Some kind of paroxysmal electrographic activity, often generalized spike and wave activity, occurred in 79% of experiments, and was accentuated by hyperventilation and photic stimulation. RÉSUMÉ On a réalisé un modèle expérimental chez 29 tortues concernant la composante thalamocorticale (centrencéphalique) dans la susceptibilityé des crises. Un foyer épileptique a été provoqué dans le thalamus par administration électrophorétique de pénicilline. Des décharges thalamiques étaient projetées sur le cortex générate ipsilatéral, quelque‐fois aussi contra‐latéral. Le foyer thalamique augmentait la durée et la fréquence des fuseaux et activait un foyer cortical à la pénicilline en racourcissant la latence de son origine et le temps entre les décharges. Quelque type ďactivitéélectrographique paroxystique souvent de pointe‐onde généralisée, apparaissait dans 79% des cas, et était accentuée par ľhyperpnée et la stimulation lumineuse intermittente. ZUSAMMENFASSUNG Bei 29 Schildkröten wurde ein experimentelles Modell der thalamocortikalen (cen‐trencephalen) Komponente der Anfallsbereitschaft induziert. Ein epileptischer Fokus wurde im Thalamus durch elektrophoretische Anwendung von Penicillin hervor‐gerufen. Die thalamischen Entladungen wurden auf den ipsilateralen, gelegentlich auch kontralateralen allgemein‐sensorischen Cortex des Vorderhirns projiziert. Der thalamische Fokus vermehrte die Dauer und Häufigkeit cortikaler Spindeln und verstärkte die Aktivität eines cortikalen Penicillinfokus durch Verkürzung der Latenzzeit seiner Entstehung und des Intervalls zwischen den Entladungen. Paro‐xysmale elektrische Entladungen–häufig generalisierte spike‐wave‐Aktivität– erfolgten in 79% der Versuche. Sie wurde durch Hyperventilation und Fotostimulation verstärkt. RESUMEN Un modelo experimental del componente talamocortical (centroencefalico) de la prediposicion a la crisis ha sido practicado en 29 tortugas. El foco epiléptico se ha provocado en el talamo mediante administración electroforética de penicilina. Las descargas talámicas se proyectaban sobre el cortex ipsilateral y alguna vez sobre el cortex contralateral. El foco talámico aumentaba la duración y la frequencia de los husos corticales y activaba un foco cortical penicilinico acortando la latencia de su origin y el tiempo de duración entre las descargas. Cierto tipo de actividad electro‐grafica paroxista, frecuentimente puntas‐ondas generalizadas aparecen en un 79% de los casos, acentuandos con la hyperventilateón y con la estimu...

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Section: Influence Of Intrathalamic Penicillin On the Development Of mentioning

confidence: 87%

“…The experiments were performed on 29 turtles, Testudo graeca L., 670-850 g in body weight. The animals were curarized and artificially ventilated ; both forebrain hemispheres were exposed by a large trephine opening (see Volanschi and Servit 1969a).…”

Section: Methodsmentioning

confidence: 99%

Experimental Thalamic Focus and Thalamocortical Epileptogenic Mechanisms in the Brain of Turtle

Servít¹,

Strejcková²

1973

Epilepsia

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“…The in vivo freeze-lesion technique used in mammals (Openchowski, 1883;Smith and Purpura, 1960;Lewin, 1972) was applied to the cerebral cortex of the pond turtle in vitro. Consistent with these similarities, turtle cortex develops epileptiform discharges when exposed to the convulsants bicuculline or penicillin (Volanschi and Servit, 1969; Shen and Kriegstein, 1986;Larson-Prior and Slater, 1988) and systemic administration of penicillin produces clonic-tonic seizure activity in turtles Nasi et al, 1986). Consistent with these similarities, turtle cortex develops epileptiform discharges when exposed to the convulsants bicuculline or penicillin (Volanschi and Servit, 1969; Shen and Kriegstein, 1986;Larson-Prior and Slater, 1988) and systemic administration of penicillin produces clonic-tonic seizure activity in turtles Nasi et al, 1986).…”

mentioning

confidence: 93%

“…Turtles and mammals share some aspects of cortical circuitry (Hall et al, 1977;Desan, 1984Desan, , 1988Ouimet et al, 1985;Ulinski, 1985;Kriegstein and Connors, 1986) and their cortical neurons have sim-ilar physiological, morphological, and biochemical properties (Smith et al, 1980;Connors and Kriegstein, 1986; Kriegstein and Connors, 1986; Kriegstein et al, 19866;Shen and Kriegstein, 1986;Blanton et al, 1987;Reiner and Oliver, 1987). Consistent with these similarities, turtle cortex develops epileptiform discharges when exposed to the convulsants bicuculline or penicillin (Volanschi and Servit, 1969; Shen and Kriegstein, 1986;Larson-Prior and Slater, 1988) and systemic administration of penicillin produces clonic-tonic seizure activity in turtles Nasi et al, 1986). Unlike the mammalian brain, however, unique structural features of the turtle brain and its resistance to anoxia (Belkin, 1963) allow the cerebral hemispheres and intact subcortical structures to be maintained, lesioned, and studied in vitro.…”

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confidence: 97%

Abnormal Action‐Potential Bursts and Synchronized, GABA‐Mediated Inhibitory Potentials in an In Vitro Model of Focal Epilepsy

1992

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Focal, freeze-induced lesions were made in isolated hemispheres of turtle cerebral cortex in vitro, permitting the investigation of epileptiform discharges in a preparation with preserved intracortical circuitry. Freeze lesions resulted in interictal discharges and occasional ictal-like events. The interictal discharges were dependent upon activation of non-NMDA excitatory amino acid receptors and were affected by but did not require NMDA receptor activation. Voltage clamp and current clamp recordings revealed abnormal bursts of low-amplitude action potentials in 36% of recorded neurons, while large, repetitive inhibitory potentials, mediated by GABAA receptors, were recorded in 90% of the neurons. Thus, prominent findings in this model include abnormalities of both excitatory and inhibitory activity. Since these changes in neuronal excitability resulted from a localized physical injury, they may resemble the changes that occur in acute posttraumatic epilepsy.

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“…Sleep stages, not studied here, are not the same as in mammals [Herman et al, 1964;Tauber et al, 1966Tauber et al, , 1968Peyrethon and Dusan-Peyrethon, 1968;Allison, 1972;Karmanova and Churnosov, 1972: Susie, 1972: Flanigan, 1973: Walker and Berger, 1973Flanigan et al, 1974;Tauber, 1974;Warner and Huggins, 1978;Monnier, 1980: Karmanova, 1982Campbell and Tobler, 1984;Huntley, 1987;Ayala-Gucrrero et al, 1988], There may be differences in the genesis of sei zure discharges [Volanschi and Servit, 1969;Strejekova, 1972, 1976;Shen and Kricgstcin, 1986;Larson-Prior and Slater, 1988]. Cellular aspects of activity in the DC and MC of a turtle have been an alyzed in detail [Connors and Kriegstein, 1986;Kriegstein and Connors, 1986;Shen and Kriegstein, 1986;Blanton et al, 1987;Schlcgel and Kriegstein, 1987], A preliminary report has appeared [Gaztelu et al, 1988].…”

Section: Introductionmentioning

confidence: 99%

Electrocorticograms of Hippocampal and Dorsal Cortex of Two Reptiles: Comparison with Possible Mammalian Homologs

1991

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To compare the ongoing electrical activity in possibly homologous structures of reptiles and mammals, the electrographic activity (micro-EEG) from major parts of the cortex of unanesthetized turtles (Pseudemys) and geckos (Gekko) was recorded with and without acute and chronic stimuli, physostigmine and atropine. Electrodes were placed in the medial cortex (MC) and in the dorsal cortex (DC), the possible homologs of the mammalian hippocampus and transitional or/and isocortex, respectively. The resting corticograms (1–50 Hz) are different in the two cortical areas. Both are wide-band; power falls steadily with frequency above a single maximum about 2 Hz. The MC has a nonrhythmic, low-voltage activity with occasional superimposed large sharp waves (LSWs), generally biphasic, 100–300 µV and lasting 0.25–0.75 s. The DC has smaller amplitudes (ca. 3–6 dB) at all frequencies and fewer LSWs. Reptilian LSWs are reminiscent of mammalian hippocampal sharp waves or spikes, a correlate of decreased arousal. The immobility-related rhythmic slow activity (theta), so characteristic of the hippocampus in a number of mammals, was not found in the cortex of either species of reptile under a variety of conditions. We cannot exclude the possibility of movement-related theta waves. Physostigmine injection does not produce theta, although it acts like an arousing stimulus, producing a disappearance of the LSWs and a substantial increase in the amplitude of the frequencies 12–24 Hz; these changes were more obvious in the DC. Atropine reversed the effects of physostigmine. Theta may represent a trait of the more highly differentiated hippocampal field of mammals. The condition represented by these reptiles, in which the EEG differs between parts of the pallium but without theta or reciprocal changes in the MC and DC, may be an earlier evolutionary stage. A distinctive reptilian EEG is not recognizable in Pseudemys and Gekko_tbut a number of differences from the EEG in familiar mammals are shared by these two neurologically quite different reptiles.

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Epileptic focus in the forebrain of the turtle

Cited by 12 publications

References 7 publications

Experimental Thalamic Focus and Thalamocortical Epileptogenic Mechanisms in the Brain of Turtle

Experimental Thalamic Focus and Thalamocortical Epileptogenic Mechanisms in the Brain of Turtle

Abnormal Action‐Potential Bursts and Synchronized, GABA‐Mediated Inhibitory Potentials in an In Vitro Model of Focal Epilepsy

Electrocorticograms of Hippocampal and Dorsal Cortex of Two Reptiles: Comparison with Possible Mammalian Homologs

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