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109 An involvement of CICR in generation of depolarizing spike-afterpotentials in pyramidal cells of rat frontal cortex
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109 Department YOUNGNAM
AN INVOLVEMENT OF CICR IN GENERs4TION OF DEPOLARIZING SPIKEAFTERPOTENTIALS IN PYRAMIDAL CELLS OF RAT FRONTAL CORTEX. of Physiology, Faculty of Medicine, Kyoto University, Kyoto 606, Japan KANG, TAKASHI
OKADA,
HARUNORI
OHMORI
Neocortical pyramidal cells display the long-lasting DAP following plateau-type Ca2+ spikes when K+ conductances are blocked by intracellular Cs +. The generation of DAP was mediated by Ca2+dependent cationic current which was expressed as a long-lasting tail current (I) at the offset of depolarization pulses under voltage clamp. In response to paired depolarization-pulses with various interpulse intervals (IPI), the late phase of the second tail-1 was larger than that of the first tail-1 at 5-10sec IPI while the second Ca2+-I was invariably smaller than the first Ca2+-I, suggesting an increase in [Ca2+]i in spite of the reduction of the second Ca2+-I. Caffeine abolished the late phase of tail-I, in association with a shift of holding current at -8OmV inwardly. Intracellular ruthenium red antagonized these effects of caffeine. It is suggested that the late phase of tail-1 is mediated by activation of CICR and that the facilitation of the late tail-1 is mediated by facilitation of CICR.
110 Department
IPSPs modulate spike backpropagation neurons. of Physiology, New York Medical College
in the dendrites of hippocampal
CA:1 pyramidal
Hiroshi Tsubokawa, William N. Ross We studied the effects of synaptic inhibition on backpropagating Na+ spikes in the apical dendrites of CA1 pyramidal neurons in slices from the rat hippocampus. Action potentials were evoked synaptically or antidromically. IPSPs evoked by stimulation in the stratum lacunosum moleculare reduced the amplitude of single spikes and spike-associated changes in Ca2+ in the distal dendrites but had little effect on the events occurred in the soma and the proximal part of the cell.
111 Department
ELECTROPHYSIOLOGICAL PROPERTIES OF DISSOCIATED NEURONS OF THE MESENCEPHALIC TRIGEMINAL NUCLEUS OF THE RAT of Physiology, Fukui Medical School, Matsuoka-Cho, Yoshida-Gun, Fukui, 910-ll., Japan
SHIGERU YOSHIDA, HIROSHI OKA Typical trigeminal mesencephalic (Me5) neurons have one process extending from the cell body, and these pseudounipolar neurons receive information from muscle spindles of masseteric muscles. The cell body of Me5 neurons, unlike other primary sensory neurons is located in the central nervous system. In the present work, Me5 neurons were dissociated fro; the rat brain, and their electrophysiological properties were studied using the whole-cell recording method under current-clamp or voltage-clamp conditions. Usually, neurons generated action potentials without a hump on the falling phase, and the excitation was mainly dependent of the activity of tetrodotoxin (TTX)-sensitive Na+ channels. Ca 2+ channels were also present, but their contribution to the action potential was negligible in most cases. When stimulated by long depolarizing pulses, most Me5 neurons showed phasic firing consisting of only one or two action potentials. Tonic firing was seen in only a few neurons.
109 Department YOUNGNAM
AN INVOLVEMENT OF CICR IN GENERs4TION OF DEPOLARIZING SPIKEAFTERPOTENTIALS IN PYRAMIDAL CELLS OF RAT FRONTAL CORTEX. of Physiology, Faculty of Medicine, Kyoto University, Kyoto 606, Japan KANG, TAKASHI
OKADA,
HARUNORI
OHMORI
Neocortical pyramidal cells display the long-lasting DAP following plateau-type Ca2+ spikes when K+ conductances are blocked by intracellular Cs +. The generation of DAP was mediated by Ca2+dependent cationic current which was expressed as a long-lasting tail current (I) at the offset of depolarization pulses under voltage clamp. In response to paired depolarization-pulses with various interpulse intervals (IPI), the late phase of the second tail-1 was larger than that of the first tail-1 at 5-10sec IPI while the second Ca2+-I was invariably smaller than the first Ca2+-I, suggesting an increase in [Ca2+]i in spite of the reduction of the second Ca2+-I. Caffeine abolished the late phase of tail-I, in association with a shift of holding current at -8OmV inwardly. Intracellular ruthenium red antagonized these effects of caffeine. It is suggested that the late phase of tail-1 is mediated by activation of CICR and that the facilitation of the late tail-1 is mediated by facilitation of CICR.
110 Department
IPSPs modulate spike backpropagation neurons. of Physiology, New York Medical College
in the dendrites of hippocampal
CA:1 pyramidal
Hiroshi Tsubokawa, William N. Ross We studied the effects of synaptic inhibition on backpropagating Na+ spikes in the apical dendrites of CA1 pyramidal neurons in slices from the rat hippocampus. Action potentials were evoked synaptically or antidromically. IPSPs evoked by stimulation in the stratum lacunosum moleculare reduced the amplitude of single spikes and spike-associated changes in Ca2+ in the distal dendrites but had little effect on the events occurred in the soma and the proximal part of the cell.
111 Department
ELECTROPHYSIOLOGICAL PROPERTIES OF DISSOCIATED NEURONS OF THE MESENCEPHALIC TRIGEMINAL NUCLEUS OF THE RAT of Physiology, Fukui Medical School, Matsuoka-Cho, Yoshida-Gun, Fukui, 910-ll., Japan
SHIGERU YOSHIDA, HIROSHI OKA Typical trigeminal mesencephalic (Me5) neurons have one process extending from the cell body, and these pseudounipolar neurons receive information from muscle spindles of masseteric muscles. The cell body of Me5 neurons, unlike other primary sensory neurons is located in the central nervous system. In the present work, Me5 neurons were dissociated fro; the rat brain, and their electrophysiological properties were studied using the whole-cell recording method under current-clamp or voltage-clamp conditions. Usually, neurons generated action potentials without a hump on the falling phase, and the excitation was mainly dependent of the activity of tetrodotoxin (TTX)-sensitive Na+ channels. Ca 2+ channels were also present, but their contribution to the action potential was negligible in most cases. When stimulated by long depolarizing pulses, most Me5 neurons showed phasic firing consisting of only one or two action potentials. Tonic firing was seen in only a few neurons.