B Sutor

CD Nicholson

JA Beavo

JR Howe

NT Florendo

English

Sutor, Bernd

Ten Bruggencate, Gerrit

Open Access LMU

M.R.Klee H.D.Lux E.-J.Speckmann (Eds.) Physiology, Pharmacology and Development of Epileptogenic Phenomena With 97 Figures and 23 Tables Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo Hong Kong Barcelona Budapest CONTENTS I B IOPHYSICAL MECHANISMS OF EPILEPTOGENIC A C T I V I T Y 1 Do Proton-Activated Transient Sodium Currents Contribute to Paroxysmal Depolarization? H. D. Lux, R. Grantyn and U. Misgeld 3 Synaptic Synchronized Burst Activity in a Hypothalamic Network. U. Misgeld and D. Swandulla 7 Synaptic Inhibition, Intrinsically Bursting Neurons and Synchronization in Neocortex. B. W. Connors and Y. Chagnac-Amitai 11 Nonsynaptic Spread of Epileptiform Activity in Rat Hippocampal Slices. U. Heinemann, D. Albrecht, G. Kohr, G. Rausche, J. Stabel and T. Wisskirchen 17 Interictal Discharges: Changes in Size of Extracellular Space in Relation to Changes in Extracellular K + and Na + Concentration. A. Lehmenkühler and A. Richter 23 Convulsant Hydroxybenzenes Differentially Modulate Α-Currents in Molluscan Neurons. L . Erdalyi 27 Analysis of the Slow Inward Current Induced by Pentylenetetrazol. A. Papp and O. Feher 31 Potassium Homeostasis in the Extracellular Space Surrounding Squid Axons during Repetitive Activity. Y. Pichon and N. J. Abbott 35 Properties of the Low-Threshold Calcium Current in Thalamic Relay Neurons:Recovery from Inactivation in Relation to the Control of Repetitive Burst Generation. R. Huguenard, D. A. Coulter and D. A. Prince 39 Free Calcium Transient and Oscillations in Nerve Cells. P. G. Kostyuk, P. V. Belan and Α. V. Tepikin 45 Intracellular Calcium Regulation and Neuronal Modulation. R. T. Kado, P. Morain, S. Berretta and C. Batini 49 Dendritic Ca 2 + Channels of Rat Purkinje Cells Maintained in Culture. J. L . Bossu, J. L . Dupont, L . Fagni and A. Feltz 53 Characterization of Chloride Channels in Pituitary Intermediate Lobe Cells: Sensitivity to Internal Calcium. 0. Taleb, J. Trouslard, M. Hamann, P. Vanderheyden and P. Feltz 57 Sprouting and Degeneration of Dendrites of the Identified Neuron B3 in the Buccal Ganglia of Helix Pomatia after Epileptic Activity. U. Altrup, A. Lücke, Α. Lehmenkühler and Ε-J. Speckmann 61 χ Temporal Coupling of Epileptic Discharges in the Buccal Ganglia of Helix Pomatia. M. Madeja, U. Altrup, A. Lehmenkühler and E.-J. Speckmann 65 I I B I O C H E M I C A L MECHANISMS OF EPILEPTOGENIC A C T I V I T Y 69 Mechanisms Underlying Enhanced Synaptic Activation of NMDA Receptors During Hippocampal Seizures. Y. Yaari, M. S. Jensen and A. Konnerth 71 Release of Intracellularly Stored Ca2+ in Hippocampal Neurons by NMDA Receptor Activation. /. Mody, K. G. Baimbridge, J.A. Shacklock and J. F. MacDonald 75 NMDA Receptor-Mediated EPSP in Developing Rat Neocortex. N. Kato, M. S. Braun, A. Artola and W. Singer 81 Role of Glutamate Receptors in Potassium-Induced Paroxysms in Rat Hippocampal Slices. M. S. Jensen and Y. Yaari 85 Excitatory Amino Acids-Induced Synaptic Plasticity in Hippocampus: Relation to the Age of Animals. 0. A. Krishtal, Α. V. Petrov, S. V. Smirnov, Ye. Sh. Yanovsky and M. C. Nowycky 89 Increase in Glutamate Responses by GABA in Neocortical and Archicortical Structures. /. Waiden, E.-J. Speckmann, D. Bingmann and H. Straub 95 The Action of Neuropeptides on Transmitter Release at the Neuromuscular Synapse. M. Abdul-Ghani, H. Meiri and R. Rahamimoff. 99 Cholecystokinin and Epileptogenesis in the Hippocampal CA3 Region. P. G. Aitken, D. B. Jaffe and J. V. Nadler 103 In Vivo and In Vitro Studies of the Epileptic Focus Induced by the Interruption of a Cortical GABA Infusion. C. Silva-Barrat, J. Champagnat, S. Brailowsky, C. Menini and R. Naquet 107 Serotonergic Attenuation of Low Ca2+ Induced Bursting in the CA1 Region of the Rat Hippocampus. A. Obenaus, J. M. Klancnik and K. G. Baimbridge I l l Excitability Changes Induced in Rat Neocortical Neurons by the Selective Blockade of a Low K^, Ca27Calmodulin - Independent cAMP - Phosphodiesterase. B. Sutor and G. ten Bruggencate 115 Action of a Phorbol Ester in the Presence of Two PKC Blockers. M. R. Klee and J. Hoyer 119 Genetically Determined Seizure Susceptibility in the Rat. M. Kunz, J. Mares' and R. Brdiäka 123 The Role of the Dentate Gyrus in Transmission of Epileptiform Activity from the Entorhinal Cortex to the Hippocampus. J. D. C. Lambert and R. S. G. Jones 127 XI Changes in Parvalbumin and Calbindin D28K Immunoreactivity in Rat Brain Following Pilocarpinc-Induced Seizures. E. A. Cavalheiro and M. Bentivoglio 131 Ι Π DEVELOPMENTAL ASPECTS OF EPILEPTOGENESIS 137 Developmental Alternations in NMDA-Mediated Excitation in Rat Visual and Somatosensory Cortex. H. J. Luhmann and D. A. Prince 139 Consequences of Epileptic Seizures in the Developing Brain. G. L Holmes, P. Mares' and S. L . Mosha 143 Epileptogenesis and the Immature Brain. I . Cortical Mechanisms. P. Mares', S. L . Moshe and G. L Holmes 147 Epileptogenesis and the Immature Brain. I I . Subcortical Mechanisms. S. L . Moshe, G. L . Holmes and P. Mares. 151 Involvement of Excitatory Amino Acid Receptors in Epileptiform Activity in the Immature Neocortex. W. L . Lee and J. J. Hablitz 155 Susceptibility to Bicuculline-Induced Seizures after Neonatal Hypoxia. M. R. deFeo, O. Mecarelli, G. Palladini, G. Cusimano, M. F. Rina and G. F. Ricci 159 Cortico-Cortical Transfer During Initial Phases of Kindling in the Rat: A Developmental Study J. Mares' and S. Trojan 163 Plasma Levels and Anticonvulsant Action of Phenytoin and Carbamazepine in Immature Rats. S. MaresOva, P. Mares', D. Maresovd, M. Pometlova and S. Trojan 167 Effect of Hypoxia on Hippocampal Afterdischarges in Young Rats. D. MaresOva and P. Mares' 171 Epileptiform Activity as Dependent and Independent Variables in Brain Maturation: A Comparison of the Effects of Chronic Tetrodotoxin and Picrotoxin Treatment on Developing Rat Neocortex Neurons Cultured in Vitro M. A. Corner and G. J. A. Ramakers 175 Motor Seizures in Immature Rats. M. Pohl, P. Mares, L . Veltsek and L . Stankova 179 Increased Epileptogenesis in the Immature Hippocampus. L. Veilsek and P. Mares 183 Changes in Lipid Metabolism in Epileptic Mirror Foci. R. Rokyta, S. Maresovd, J. Veliskova, V. Kubik and K. Bernäskovä 187 XII I V ANTICONVULSANT DRUG ACTIONS 191 Anticonvulsant Drug Mechanisms. W. Löscher. 193 Mechanism of Block of Thalamic T-Type Ca2+ Channels by Petit Mai Anticonvulsants D. A. Coulter, J. R. Huguenard and D. A. Prince 201 CGP 37849 / CGP 39551: The First Competitive NMDA Receptor Antagonists Suitable for Oral Antiepileptic Therapy. M. Schmutz, C. Portet, H. R. Olpe, Κ. Klebs, A. Jeker, R. Heckendorn, G. E. Fagg and H. Allgeier 205 Effects of Anticonvulsant Compounds on Voltage-and Neurotransmitter-Activated Sodium Conductances of Central Neurons in Cell Culture. M . / . McLean and A. W. Wamil 211 Memantine: Suppression of High Frequency Action Potentials Is Caused by Prolongation of the Sodium Current Refractory Period. R. Netzer, T. Binscheck, R. Koch and H. Bigalke 217 Different Dose-Dependent Actions of Memantine on Hippocampal Neurons. L . Wagner, M. R. Klee and M. L . Zeise 223 Suppression of Partial and Generalized Seizure Activity by Intracerebroventricular Perfusion of the Organic Calcium Antagonist Verapamil in the Rat. E. -J. Speckmann and J. Waiden 229 Differential Antiepileptic Effects of Organic Calcium Antagonists in CA3 Neurons of Hippocampal Slices and in Neurons of Organotypic Neuronal Explants. D. Bingmann, E.-J. Speckmann, J. Waiden, Η. Straub, R.E. Baker and J. Ruijter 233 Phenytoin and Carbamazepine Act by Accumulating Inactivated Sodium Channels. /. R. Schwarz 237 Flurazepam Reduces Axonal Conduction Velocity and Blocks Propagation of High-Frequency Discharges. J. Hoy er 241 Effects of Isoflurane and Enflurane on Focal Epileptic Paroxysms. H. Pockberger, K. Lindner and H. Petsche 245 Anticonvulsant Actions on Hippocampal Slices. C. Psarropoulou and H. L . Haas 251 Is There a Glycinergic Component in the Mechanisms of Action of Common Antiepileptic Drugs? S. J. Czuczwar, D. Wlodarczyk, M. Gasior and Z. Kleinrok 255 Developmental Defects in El Mouse Neurons and Their Normalization by a New Antiepileptic Drug, TJ-960. E. Sugaya, A. Sugaya, K. Kajiwara, T. Tsuda, H. Takagi, K. Yasuda and T. Takagi 259 SUBJECT INDEX 263 Excitability Changes Induced in Rat Neocortical Neurons by the Selective Blockade of a Low K m , Ca 27Calmodulin -Independent cAMP - Phosphodiesterase B. Sutor and G. ten Bruggencate Institute of Physiology, University of Munich, Munich, FRG Introduction By analogy with the effects of neurotransmitters, the action of the intracellular second messenger cyclic adenosine-3\5'-monophosphate (cAMP) has to be terminated by an efficient and effectively regulated inactivation mechanism. Cyclic AMP is degraded by cAMP - phosphodiesterases (cAMP -PDE). Thus, the regulation of the activity of cAMP - PDE may be of crucial importance for normal neuronal excitability as well as for the development of abnormal neuronal behavior, including epilepsies. PDEs are a family of isozymes differing in their biochemical and pharmacological properties (Beavo 1988). The availability of selective inhibitors for a low K^, Ca27calmodulin-independent isozyme (e.g., denbufylline, see Nicholson et al. 1989) allows one to study the influence of this cAMP - PDE isozyme on the excitability of rat neocortical neurons in vitro. Methods Coronal slices (500 μπι) were prepared from the frontal cortex of male Wistar rats (120 - 160 g). in the recording chamber, the slices were kept submerged in artificial CSF consisting of (in mM): 124 NaCl, 3 KCl, 1.25 NaH 2P0 4 , 2.0.CaCl2, 1.3 MgCl 2 , 25 NaHC0 3 , and 10 glucose (continuously gassed with 5% C 0 2 in 0 2 ; pH 7.4 at 32°C). Intracellular recordings were made from superficially located neurons (layer I I and III) by means of glass microelectrodes filled with either 4 Μ potassium acetate (pH 7.2) or 3 Μ KCL Postsynaptic potentials were evoked by electrical stimulation using a bipolar silver electrode positioned in cortical layer IV. Stimuli were applied at a frequency of 0.1 Hz. In the present study, the stimulus intensities (30 - 300 μΑ) are given as multiples of the threshold intensity (T) necessary to evoke an action potential. Denbufylline (DBF) was dissolved in dimethyl sulfoxide (DMSO) at concentrations of 10*2M. From this stock solution, appropriate amounts were added to the bathing solution in order to obtain the desired drug concentration. The final solvent concentration never exceeded 0.1%. At this concentration, DMSO did not affect the neuronal electrophysiological properties. Results The results are based on intracellular recordings from 25 cortical neurons with a mean resting potential of -79.6 ± 3.2 mV (mean ± SD) and a mean input resistance of 26.5 ± 2.3 ΜΩ. When added to the bathing solution at concentrations between 10 and 100 nM, DBF increased the amplitude of excitatory postsynaptic potentials (EPSPs). Figure 1 depicts an example of DBF-induced changes of EPSPs. At low stimulus intensities (0.4 T, Fig. 1A), this neuron responded with an early EPSP (eEPSP, control trace). Following the application of DBF (100 nM, center trace), the amplitude of the eEPSP increased and a late EPSP (1EPSP) occurred. Upon an increase in stimulus strength to 0.5 Τ (Fig. IB) , an eEPSP followed by a small 1EPSP was observed (see Sutor and Hablitz 1989). Again, DBF (100 nM) produced an enhancement in the amplitude of both EPSPs and, in addition, a decrease in the latency of the 1EPSP (center trace). These DBF-induced Experimental Brain Research Series 20 © Springer-Verlag Berlin · Heidelberg 1991 116 A control DBF , 1OOnM, 15min wash, 60min 10mV 0 . 5 T Fig. 1A,B. Actions of DBF (100 nM) on EPSPs in rat neocortical neurons. The resting potential was -85 mV. EPSPs were evoked by electrical stimulation of cortical layer IV using different stimulus strength (A and B). The time point of stimulation is indicated by the stimulus artifact. Stimulus intensities are given as multiples of 1 Τ changes of EPSPs were reversible upon washout of the drug (Fig. 1A and B, right traces). At these low concentrations (10 - 100 nM) no significant DBF-induced effects on inhibitory postsynaptic potentials (EPSPs) were observed. However, at higher concentrations (1 - 10μΜ), DBF produced a marked prolongation of GABAergic, CI"-dependent IPSPs (Fig. 2). At a stimulus strength of 0.5 Τ (Fig. 2A), an eEPSP was observed (control trace), the amplitude of which was enhanced following the application of DBF (10 μΜ). Stimulation with an intensity of 0.9 Τ (Fig. 2B) evoked a sequence of postsynaptic potentials consisting of an EPSP followed by a depolarizing, CT-dependent IPSP and a small hyperpolarizing, K+-dependent IPSP (control trace, see Howe et al. 1987). In the presence of DBF (10 μΜ), both the amplitude of the EPSP and the duration of the depolarizing IPSP increased (center trace; see also superimposed traces). At a stimulus intensity of 1 Τ (Fig. 2C), the DBF-induced effects were similar to those observed at 0.9 T. The action of DBF on the depolarizing IPSP was reversible upon washout of the drug. DBF affected neither the membrane potential nor the input resistance (measured with hyperpolarizing current pulses). In the depolarizing direction, a slight enhancement of the steady state inward rectification (see Sutor and Zieglgänsberger 1987) was observed. The latter effect is probably responsible for the DBF-induced increase in direct excitability. Discussion These experiments demonstrate a concentration-dependent effects of the selective cAMP - PDE inhibitor, DBF, on synaptic potentials in rat neocortical neurons. At low concentrations, DBF facilitates excitatory synaptic transmission without affecting inhibitory transmission. At higher concentrations, DBF predominantly prolongs the duration of GABAergic, Cl-dependent IPSPs. In this context, two other observations are of interest: (1) In cytochemical studies, we were able to show that the cAMP - PDE activity is predominantly located in the postsynaptic density of axospineous or axodendritic synapses of cortical neurons (see also Florendo et al. 1971) and (2) by measuring the effects of DBF on the total PDE activity in rat frontal cortex we found that at concentrations which effectively facilitate synaptic transmission (up to 10 μΜ), only a maximum of 10% of the total PDE activity was blocked. These results suggest that the low Ca27calmodulin-independent cAMP - PDE might be of enormous importance for synaptic transmission in the neocortex. The ultrastructural localization of most of the PDE activity and the 117 A control D B F , 1 0 μ Μ , 10min superimposed L O T Fig. 2A-C. Actions of DBF (10 μΜ) on IPSPs in rat neocortical neurons. The resting potential was -81 mV. A At an intensity of 0.5 T, the stimulus produced an EPSP (control) the amplitude of which increased upon application of DBF. In this and the following two panels, the single recordings were superimposed and are shown on the right-hand side of the figure. Β At a just subthreshold stimulus intensity (0.9 T), the stimulus evoked an EPSP/TPSP sequence. GABA-mediated, Cl'-dependent EPSPs display a depolarizing time course in rat neocortical neurons in vitro. C At 1.0 T, the stimulus induced a slowly decaying depolarizing IPSP following the synaptically evoked action potential. Note the enhancing effect of DBF on the EPSP duration observation that the inhibition of only a small fraction of the total PDE activity leads to marked facilitation of synaptic transmission suggest that the low K m cAMP - PDE is located at a "strategically" significant site and that this isozyme might be the determining factor in the regulation of intracellular cAMP concentration in the synaptic region. Acknowledgements. This work was supported by the Deutsche Forschungsgemeinschaft (Su 104/1-1 ana SFB 220, A9). References Beavo JA (1988) Multiple isozymes of cyclic nucleotide phosphodiesterase. Adv in Second Messenger and Phosphoprotein Res 22: 1-38 Florendo NT, Barrnett RJ, Greengard Ρ (1971) Cyclic 3',5*-nucleotide phosphodiesterase: cytochemical localization in cerebral cortex. Science 173: 745-747 Howe JR, Sutor B, Zieglgänsberger W (1987) Baclofen reduces post-synaptic potentials of rat cortical neurones by an action other than its hyperpolarizing action. J Physiol 384: 539-569 Nicholson CD, Jackman SA, Wilke R (1989) The ability of denbufylline to inhibit cyclic nucleotide phosphodiesterase and its affinity for adenosine receptors and the adenosine re-uptake site. Br J Pharmacol 97: 889-897 118 Sutor Β, Hablitz JJ (1989) EPSPs in rat neocortical neurons in vitro. I . Electrophysiological evidence for two distinct EPSPs. J Ncurophysiol 61: 607-620 Sutor B, Zieglgänsberger W (1987) A low-voltage activated, transient calcium current is responsible for the time-dependent depolarizing inward rectification of rat neocortical neurons in vitro. Pflügers Arch 410: 102-111 

Multiple isozymes of cyclic nucleotide phosphodiesterase.

Excitability changes induced in rat neo-cortical neurons by the selective blockade of a low KM, Ca2+/calmodulin-independent cAMP-phosphodiesterase.

B. Sutor

G. Bruggencate

Crossref

Excitability Changes Induced in Rat Neocortical Neurons by the Selective Blockade of a Low Km, Ca2+/Calmodulin — Independent cAMP — Phosphodiesterase

Universität München: Elektronischen Publikationen

M.R.Klee H.D.Lux E.-J.Speckmann (Eds.) 
Physiology, Pharmacology 
and Development 
of Epileptogenic Phenomena 
With 97 Figures and 23 Tables 
Springer-Verlag 
Berlin Heidelberg NewYork 
London Paris Tokyo 
Hong Kong Barcelona 
Budapest 
CONTENTS 
I B IOPHYSICAL MECHANISMS OF EPILEPTOGENIC A C T I V I T Y 1 
Do Proton-Activated Transient Sodium Currents Contribute to Paroxysmal 
Depolarization? 
H. D. Lux, R. Grantyn and U. Misgeld 3 
Synaptic Synchronized Burst Activity in a Hypothalamic Network. 
U. Misgeld and D. Swandulla 7 
Synaptic Inhibition, Intrinsically Bursting Neurons and Synchronization in Neocortex. 
B. W. Connors and Y. Chagnac-Amitai 11 
Nonsynaptic Spread of Epileptiform Activity in Rat Hippocampal Slices. 
U. Heinemann, D. Albrecht, G. Kohr, G. Rausche, J. Stabel and T. Wisskirchen 17 
Interictal Discharges: Changes in Size of Extracellular Space in Relation to Changes 
in Extracellular K + and Na + Concentration. 
A. Lehmenkühler and A. Richter 23 
Convulsant Hydroxybenzenes Differentially Modulate Α-Currents in Molluscan Neurons. 
L . Erdalyi 27 
Analysis of the Slow Inward Current Induced by Pentylenetetrazol. 
A. Papp and O. Feher 31 
Potassium Homeostasis in the Extracellular Space Surrounding Squid Axons during 
Repetitive Activity. 
Y. Pichon and N. J. Abbott 35 
Properties of the Low-Threshold Calcium Current in Thalamic Relay Neurons:Recovery 
from Inactivation in Relation to the Control of Repetitive Burst Generation. 
R. Huguenard, D. A. Coulter and D. A. Prince 39 
Free Calcium Transient and Oscillations in Nerve Cells. 
P. G. Kostyuk, P. V. Belan and Α. V. Tepikin 45 
Intracellular Calcium Regulation and Neuronal Modulation. 
R. T. Kado, P. Morain, S. Berretta and C. Batini 49 
Dendritic Ca 2 + Channels of Rat Purkinje Cells Maintained in Culture. 
J. L . Bossu, J. L . Dupont, L . Fagni and A. Feltz 53 
Characterization of Chloride Channels in Pituitary Intermediate Lobe Cells: Sensitivity 
to Internal Calcium. 
0. Taleb, J. Trouslard, M. Hamann, P. Vanderheyden and P. Feltz 57 
Sprouting and Degeneration of Dendrites of the Identified Neuron B3 in the Buccal 
Ganglia of Helix Pomatia after Epileptic Activity. 
U. Altrup, A. Lücke, Α. Lehmenkühler and Ε-J. Speckmann 61 
χ 
Temporal Coupling of Epileptic Discharges in the Buccal Ganglia of Helix Pomatia. 
M. Madeja, U. Altrup, A. Lehmenkühler and E.-J. Speckmann 65 
I I B I O C H E M I C A L MECHANISMS OF EPILEPTOGENIC A C T I V I T Y 69 
Mechanisms Underlying Enhanced Synaptic Activation of NMDA Receptors During 
Hippocampal Seizures. 
Y. Yaari, M. S. Jensen and A. Konnerth 71 
Release of Intracellularly Stored Ca2+ in Hippocampal Neurons by NMDA 
Receptor Activation. 
/. Mody, K. G. Baimbridge, J.A. Shacklock and J. F. MacDonald 75 
NMDA Receptor-Mediated EPSP in Developing Rat Neocortex. 
N. Kato, M. S. Braun, A. Artola and W. Singer 81 
Role of Glutamate Receptors in Potassium-Induced Paroxysms in Rat Hippocampal Slices. 
M. S. Jensen and Y. Yaari 85 
Excitatory Amino Acids-Induced Synaptic Plasticity in Hippocampus: Relation to 
the Age of Animals. 
0. A. Krishtal, Α. V. Petrov, S. V. Smirnov, Ye. Sh. Yanovsky and M. C. Nowycky 89 
Increase in Glutamate Responses by GABA in Neocortical and Archicortical Structures. 
/. Waiden, E.-J. Speckmann, D. Bingmann and H. Straub 95 
The Action of Neuropeptides on Transmitter Release at the Neuromuscular Synapse. 
M. Abdul-Ghani, H. Meiri and R. Rahamimoff. 99 
Cholecystokinin and Epileptogenesis in the Hippocampal CA3 Region. 
P. G. Aitken, D. B. Jaffe and J. V. Nadler 103 
In Vivo and In Vitro Studies of the Epileptic Focus Induced by the Interruption of 
a Cortical GABA Infusion. 
C. Silva-Barrat, J. Champagnat, S. Brailowsky, C. Menini and R. Naquet 107 
Serotonergic Attenuation of Low Ca2+ Induced Bursting in the CA1 Region of the Rat 
Hippocampus. 
A. Obenaus, J. M. Klancnik and K. G. Baimbridge I l l 
Excitability Changes Induced in Rat Neocortical Neurons by the Selective Blockade 
of a Low K^, Ca27Calmodulin - Independent cAMP - Phosphodiesterase. 
B. Sutor and G. ten Bruggencate 115 
Action of a Phorbol Ester in the Presence of Two PKC Blockers. 
M. R. Klee and J. Hoyer 119 
Genetically Determined Seizure Susceptibility in the Rat. 
M. Kunz, J. Mares' and R. Brdiäka 123 
The Role of the Dentate Gyrus in Transmission of Epileptiform Activity from the 
Entorhinal Cortex to the Hippocampus. 
J. D. C. Lambert and R. S. G. Jones 127 
XI 
Changes in Parvalbumin and Calbindin D28K Immunoreactivity in Rat Brain 
Following Pilocarpinc-Induced Seizures. 
E. A. Cavalheiro and M. Bentivoglio 131 
Ι Π DEVELOPMENTAL ASPECTS OF EPILEPTOGENESIS 137 
Developmental Alternations in NMDA-Mediated Excitation in Rat Visual and 
Somatosensory Cortex. 
H. J. Luhmann and D. A. Prince 139 
Consequences of Epileptic Seizures in the Developing Brain. 
G. L Holmes, P. Mares' and S. L . Mosha 143 
Epileptogenesis and the Immature Brain. I . Cortical Mechanisms. 
P. Mares', S. L . Moshe and G. L Holmes 147 
Epileptogenesis and the Immature Brain. I I . Subcortical Mechanisms. 
S. L . Moshe, G. L . Holmes and P. Mares. 151 
Involvement of Excitatory Amino Acid Receptors in Epileptiform Activity 
in the Immature Neocortex. 
W. L . Lee and J. J. Hablitz 155 
Susceptibility to Bicuculline-Induced Seizures after Neonatal Hypoxia. 
M. R. deFeo, O. Mecarelli, G. Palladini, G. Cusimano, M. F. Rina and G. F. Ricci 159 
Cortico-Cortical Transfer During Initial Phases of Kindling in the Rat: 
A Developmental Study 
J. Mares' and S. Trojan 163 
Plasma Levels and Anticonvulsant Action of Phenytoin and Carbamazepine in 
Immature Rats. 
S. MaresOva, P. Mares', D. Maresovd, M. Pometlova and S. Trojan 167 
Effect of Hypoxia on Hippocampal Afterdischarges in Young Rats. 
D. MaresOva and P. Mares' 171 
Epileptiform Activity as Dependent and Independent Variables in Brain Maturation: 
A Comparison of the Effects of Chronic Tetrodotoxin and Picrotoxin Treatment on 
Developing Rat Neocortex Neurons Cultured in Vitro 
M. A. Corner and G. J. A. Ramakers 175 
Motor Seizures in Immature Rats. 
M. Pohl, P. Mares, L . Veltsek and L . Stankova 179 
Increased Epileptogenesis in the Immature Hippocampus. 
L. Veilsek and P. Mares 183 
Changes in Lipid Metabolism in Epileptic Mirror Foci. 
R. Rokyta, S. Maresovd, J. Veliskova, V. Kubik and K. Bernäskovä 187 
XII 
I V ANTICONVULSANT DRUG ACTIONS 191 
Anticonvulsant Drug Mechanisms. 
W. Löscher. 193 
Mechanism of Block of Thalamic T-Type Ca2+ Channels by Petit Mai Anticonvulsants 
D. A. Coulter, J. R. Huguenard and D. A. Prince 201 
CGP 37849 / CGP 39551: The First Competitive NMDA Receptor Antagonists 
Suitable for Oral Antiepileptic Therapy. 
M. Schmutz, C. Portet, H. R. Olpe, Κ. Klebs, A. Jeker, R. Heckendorn, G. E. Fagg 
and H. Allgeier 205 
Effects of Anticonvulsant Compounds on Voltage-and Neurotransmitter-Activated 
Sodium Conductances of Central Neurons in Cell Culture. 
M . / . McLean and A. W. Wamil 211 
Memantine: Suppression of High Frequency Action Potentials Is Caused by 
Prolongation of the Sodium Current Refractory Period. 
R. Netzer, T. Binscheck, R. Koch and H. Bigalke 217 
Different Dose-Dependent Actions of Memantine on Hippocampal Neurons. 
L . Wagner, M. R. Klee and M. L . Zeise 223 
Suppression of Partial and Generalized Seizure Activity by Intracerebroventricular 
Perfusion of the Organic Calcium Antagonist Verapamil in the Rat. 
E. -J. Speckmann and J. Waiden 229 
Differential Antiepileptic Effects of Organic Calcium Antagonists in CA3 Neurons 
of Hippocampal Slices and in Neurons of Organotypic Neuronal Explants. 
D. Bingmann, E.-J. Speckmann, J. Waiden, Η. Straub, R.E. Baker and J. Ruijter 233 
Phenytoin and Carbamazepine Act by Accumulating Inactivated Sodium Channels. 
/. R. Schwarz 237 
Flurazepam Reduces Axonal Conduction Velocity and Blocks Propagation of 
High-Frequency Discharges. 
J. Hoy er 241 
Effects of Isoflurane and Enflurane on Focal Epileptic Paroxysms. 
H. Pockberger, K. Lindner and H. Petsche 245 
Anticonvulsant Actions on Hippocampal Slices. 
C. Psarropoulou and H. L . Haas 251 
Is There a Glycinergic Component in the Mechanisms of Action of Common 
Antiepileptic Drugs? 
S. J. Czuczwar, D. Wlodarczyk, M. Gasior and Z. Kleinrok 255 
Developmental Defects in El Mouse Neurons and Their Normalization by a New 
Antiepileptic Drug, TJ-960. 
E. Sugaya, A. Sugaya, K. Kajiwara, T. Tsuda, H. Takagi, K. Yasuda and T. Takagi 259 
SUBJECT INDEX 263 
Excitability Changes Induced in Rat Neocortical Neurons 
by the Selective Blockade of a Low K m , Ca 27Calmodulin -
Independent cAMP - Phosphodiesterase 
B. Sutor and G. ten Bruggencate 
Institute of Physiology, University of Munich, Munich, FRG 
Introduction 
By analogy with the effects of neurotransmitters, the action of the intracellular second messenger 
cyclic adenosine-3\5'-monophosphate (cAMP) has to be terminated by an efficient and effectively 
regulated inactivation mechanism. Cyclic AMP is degraded by cAMP - phosphodiesterases (cAMP -
PDE). Thus, the regulation of the activity of cAMP - PDE may be of crucial importance for 
normal neuronal excitability as well as for the development of abnormal neuronal behavior, 
including epilepsies. PDEs are a family of isozymes differing in their biochemical and 
pharmacological properties (Beavo 1988). The availability of selective inhibitors for a low K^, 
Ca27calmodulin-independent isozyme (e.g., denbufylline, see Nicholson et al. 1989) allows one to 
study the influence of this cAMP - PDE isozyme on the excitability of rat neocortical neurons in 
vitro. 
Methods 
Coronal slices (500 μπι) were prepared from the frontal cortex of male Wistar rats (120 - 160 g). 
in the recording chamber, the slices were kept submerged in artificial CSF consisting of (in mM): 
124 NaCl, 3 KCl, 1.25 NaH 2P0 4 , 2.0.CaCl2, 1.3 MgCl 2 , 25 NaHC0 3 , and 10 glucose (continuously 
gassed with 5% C 0 2 in 0 2 ; pH 7.4 at 32°C). Intracellular recordings were made from superficially 
located neurons (layer I I and III) by means of glass microelectrodes filled with either 4 Μ 
potassium acetate (pH 7.2) or 3 Μ KCL Postsynaptic potentials were evoked by electrical 
stimulation using a bipolar silver electrode positioned in cortical layer IV. Stimuli were applied at 
a frequency of 0.1 Hz. In the present study, the stimulus intensities (30 - 300 μΑ) are given as 
multiples of the threshold intensity (T) necessary to evoke an action potential. Denbufylline (DBF) 
was dissolved in dimethyl sulfoxide (DMSO) at concentrations of 10*2M. From this stock solution, 
appropriate amounts were added to the bathing solution in order to obtain the desired drug 
concentration. The final solvent concentration never exceeded 0.1%. At this concentration, DMSO 
did not affect the neuronal electrophysiological properties. 
Results 
The results are based on intracellular recordings from 25 cortical neurons with a mean resting 
potential of -79.6 ± 3.2 mV (mean ± SD) and a mean input resistance of 26.5 ± 2.3 ΜΩ. When 
added to the bathing solution at concentrations between 10 and 100 nM, DBF increased the 
amplitude of excitatory postsynaptic potentials (EPSPs). Figure 1 depicts an example of DBF-
induced changes of EPSPs. At low stimulus intensities (0.4 T, Fig. 1A), this neuron responded with 
an early EPSP (eEPSP, control trace). Following the application of DBF (100 nM, center trace), 
the amplitude of the eEPSP increased and a late EPSP (1EPSP) occurred. Upon an increase in 
stimulus strength to 0.5 Τ (Fig. IB) , an eEPSP followed by a small 1EPSP was observed (see Sutor 
and Hablitz 1989). Again, DBF (100 nM) produced an enhancement in the amplitude of both 
EPSPs and, in addition, a decrease in the latency of the 1EPSP (center trace). These DBF-induced 
Experimental Brain Research Series 20 
© Springer-Verlag Berlin · Heidelberg 1991 
116 
A control DBF , 1OOnM, 15min wash, 60min 
10mV 
0 . 5 T 
Fig. 1A,B. Actions of DBF (100 nM) on EPSPs in rat neocortical neurons. The resting potential was -85 mV. 
EPSPs were evoked by electrical stimulation of cortical layer IV using different stimulus strength (A and B). 
The time point of stimulation is indicated by the stimulus artifact. Stimulus intensities are given as multiples 
of 1 Τ 
changes of EPSPs were reversible upon washout of the drug (Fig. 1A and B, right traces). At these 
low concentrations (10 - 100 nM) no significant DBF-induced effects on inhibitory postsynaptic 
potentials (EPSPs) were observed. However, at higher concentrations (1 - 10μΜ), DBF produced 
a marked prolongation of GABAergic, CI"-dependent IPSPs (Fig. 2). At a stimulus strength of 0.5 
Τ (Fig. 2A), an eEPSP was observed (control trace), the amplitude of which was enhanced 
following the application of DBF (10 μΜ). Stimulation with an intensity of 0.9 Τ (Fig. 2B) evoked 
a sequence of postsynaptic potentials consisting of an EPSP followed by a depolarizing, CT-
dependent IPSP and a small hyperpolarizing, K+-dependent IPSP (control trace, see Howe et al. 
1987). In the presence of DBF (10 μΜ), both the amplitude of the EPSP and the duration of the 
depolarizing IPSP increased (center trace; see also superimposed traces). At a stimulus intensity of 
1 Τ (Fig. 2C), the DBF-induced effects were similar to those observed at 0.9 T. The action of DBF 
on the depolarizing IPSP was reversible upon washout of the drug. 
DBF affected neither the membrane potential nor the input resistance (measured with 
hyperpolarizing current pulses). In the depolarizing direction, a slight enhancement of the steady 
state inward rectification (see Sutor and Zieglgänsberger 1987) was observed. The latter effect is 
probably responsible for the DBF-induced increase in direct excitability. 
Discussion 
These experiments demonstrate a concentration-dependent effects of the selective cAMP - PDE 
inhibitor, DBF, on synaptic potentials in rat neocortical neurons. At low concentrations, DBF 
facilitates excitatory synaptic transmission without affecting inhibitory transmission. At higher 
concentrations, DBF predominantly prolongs the duration of GABAergic, Cl-dependent IPSPs. In 
this context, two other observations are of interest: (1) In cytochemical studies, we were able to 
show that the cAMP - PDE activity is predominantly located in the postsynaptic density of 
axospineous or axodendritic synapses of cortical neurons (see also Florendo et al. 1971) and (2) 
by measuring the effects of DBF on the total PDE activity in rat frontal cortex we found that at 
concentrations which effectively facilitate synaptic transmission (up to 10 μΜ), only a maximum 
of 10% of the total PDE activity was blocked. These results suggest that the low 
Ca27calmodulin-independent cAMP - PDE might be of enormous importance for synaptic 
transmission in the neocortex. The ultrastructural localization of most of the PDE activity and the 
117 
A control D B F , 1 0 μ Μ , 10min superimposed 
L O T 
Fig. 2A-C. Actions of DBF (10 μΜ) on IPSPs in rat neocortical neurons. The resting potential was -81 mV. 
A At an intensity of 0.5 T, the stimulus produced an EPSP (control) the amplitude of which increased upon 
application of DBF. In this and the following two panels, the single recordings were superimposed and are 
shown on the right-hand side of the figure. Β At a just subthreshold stimulus intensity (0.9 T), the stimulus 
evoked an EPSP/TPSP sequence. GABA-mediated, Cl'-dependent EPSPs display a depolarizing time course 
in rat neocortical neurons in vitro. C At 1.0 T, the stimulus induced a slowly decaying depolarizing IPSP 
following the synaptically evoked action potential. Note the enhancing effect of DBF on the EPSP duration 
observation that the inhibition of only a small fraction of the total PDE activity leads to marked 
facilitation of synaptic transmission suggest that the low K m cAMP - PDE is located at a 
"strategically" significant site and that this isozyme might be the determining factor in the 
regulation of intracellular cAMP concentration in the synaptic region. 
Acknowledgements. This work was supported by the Deutsche Forschungsgemeinschaft (Su 104/1-1 ana SFB 
220, A9). 
References 
Beavo JA (1988) Multiple isozymes of cyclic nucleotide phosphodiesterase. Adv in Second Messenger and 
Phosphoprotein Res 22: 1-38 
Florendo NT, Barrnett RJ, Greengard Ρ (1971) Cyclic 3',5*-nucleotide phosphodiesterase: cytochemical 
localization in cerebral cortex. Science 173: 745-747 
Howe JR, Sutor B, Zieglgänsberger W (1987) Baclofen reduces post-synaptic potentials of rat cortical 
neurones by an action other than its hyperpolarizing action. J Physiol 384: 539-569 
Nicholson CD, Jackman SA, Wilke R (1989) The ability of denbufylline to inhibit cyclic nucleotide 
phosphodiesterase and its affinity for adenosine receptors and the adenosine re-uptake site. Br J 
Pharmacol 97: 889-897 
118 
Sutor Β, Hablitz JJ (1989) EPSPs in rat neocortical neurons in vitro. I . Electrophysiological evidence for two 
distinct EPSPs. J Ncurophysiol 61: 607-620 
Sutor B, Zieglgänsberger W (1987) A low-voltage activated, transient calcium current is responsible for the 
time-dependent depolarizing inward rectification of rat neocortical neurons in vitro. Pflügers Arch 410: 
102-111 


https://epub.ub.uni-muenchen.de/6111/1/6111.pdf

Excitability changes induced in rat neo-cortical neurons by the selective blockade of a low KM, Ca2+/calmodulin-independent cAMP-phosphodiesterase.

Abstract

Similar works

Full text

Available Versions

Open Access LMU

Crossref

Universität München: Elektronischen Publikationen