Endogenous pacemaker potentials develop into paroxysmal depolarization shifts (PDSs) with application of an epileptogenic drug. 2003

Ulrich Altrup, and Marc Häder, and Ulrich Storz
Institut für Experimentelle Epilepsieforschung, University of Münster, Hüfferstrasse 68, 48149 Münster, Germany. altrup@uni-muenster.de

Well-known invertebrate ganglia (buccal ganglia of Helix pomatia, abdominal ganglia of Aplysia californica) were used to study the contribution of synaptic potentials, central pattern generators, and endogenously generated neuronal potentials to the development of epileptiform activity. Epileptiform activity which was induced with application of pentylenetetrazol (1 to 100 mM) or etomidate (0.12 to 1.0 mM) consisted of paroxysmal depolarization shifts (PDSs) recorded simultaneously from several identified neurons with sharp microelectrodes. With application of an epileptogenic drug, endogenous pacemaker potentials develop into PDSs. With increasing concentration of the drug, (i) amplitude of pacemaker-depolarizations and (ii) delay of pacemaker-repolarization increased progressively finally resulting in PDSs. Additionally, the activation characterists of currents shifted from between -50 and -40 mV (pacemaker potentials, control conditions) to between -100 and -40 mV (PDS, epileptic conditions). Only neurons which generated pacemaker potentials under control conditions could generate PDSs under epileptic conditions. Chemical synaptic inputs triggered or blocked pacemaker potentials as well as PDSs. Activities induced from central pattern generators were identified with simultaneous recordings from several identified neurons. The central pattern generators could trigger or block pacemaker potentials as well as PDSs. Results demonstrate that, in the used model nervous systems, pacemaker potentials which are generated by the single neurons are the physiologic basis of epileptic activity.

UI MeSH Term Description Entries
D008839 Microelectrodes Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed) Electrodes, Miniaturized,Electrode, Miniaturized,Microelectrode,Miniaturized Electrode,Miniaturized Electrodes
D009435 Synaptic Transmission The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES. Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D010433 Pentylenetetrazole A pharmaceutical agent that displays activity as a central nervous system and respiratory stimulant. It is considered a non-competitive GAMMA-AMINOBUTYRIC ACID antagonist. Pentylenetetrazole has been used experimentally to study seizure phenomenon and to identify pharmaceuticals that may control seizure susceptibility. Leptazole,Pentamethylenetetrazole,Pentetrazole,Cardiazol,Corasol,Corazol,Corazole,Korazol,Korazole,Metrazol,Metrazole,Pentazol,Pentylenetetrazol
D003292 Convulsants Substances that act in the brain stem or spinal cord to produce tonic or clonic convulsions, often by removing normal inhibitory tone. They were formerly used to stimulate respiration or as antidotes to barbiturate overdose. They are now most commonly used as experimental tools. Convulsant,Convulsant Effect,Convulsant Effects,Effect, Convulsant,Effects, Convulsant
D004558 Electric Stimulation Use of electric potential or currents to elicit biological responses. Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004827 Epilepsy A disorder characterized by recurrent episodes of paroxysmal brain dysfunction due to a sudden, disorderly, and excessive neuronal discharge. Epilepsy classification systems are generally based upon: (1) clinical features of the seizure episodes (e.g., motor seizure), (2) etiology (e.g., post-traumatic), (3) anatomic site of seizure origin (e.g., frontal lobe seizure), (4) tendency to spread to other structures in the brain, and (5) temporal patterns (e.g., nocturnal epilepsy). (From Adams et al., Principles of Neurology, 6th ed, p313) Aura,Awakening Epilepsy,Seizure Disorder,Epilepsy, Cryptogenic,Auras,Cryptogenic Epilepsies,Cryptogenic Epilepsy,Epilepsies,Epilepsies, Cryptogenic,Epilepsy, Awakening,Seizure Disorders
D006372 Helix, Snails A genus of chiefly Eurasian and African land snails including the principal edible snails as well as several pests of cultivated plants. Helix (Snails),Snails Helix
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001048 Aplysia An opisthobranch mollusk of the order Anaspidea. It is used frequently in studies of nervous system development because of its large identifiable neurons. Aplysiatoxin and its derivatives are not biosynthesized by Aplysia, but acquired by ingestion of Lyngbya (seaweed) species. Aplysias
D001683 Biological Clocks The physiological mechanisms that govern the rhythmic occurrence of certain biochemical, physiological, and behavioral phenomena. Biological Oscillators,Oscillators, Endogenous,Pacemakers, Biological,Biologic Clock,Biologic Oscillator,Biological Pacemakers,Clock, Biologic,Clocks, Biological,Oscillator, Biologic,Oscillators, Biological,Pacemaker, Biologic,Pacemakers, Biologic,Biologic Clocks,Biologic Oscillators,Biologic Pacemaker,Biologic Pacemakers,Biological Clock,Biological Oscillator,Biological Pacemaker,Clock, Biological,Clocks, Biologic,Endogenous Oscillator,Endogenous Oscillators,Oscillator, Biological,Oscillator, Endogenous,Oscillators, Biologic,Pacemaker, Biological

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