- Email: [email protected]
118 Single channel analysis in rat hippocampal neurons at application of phosphatase inhibitor fk506
S23 118
SINGLE CHANNELANALYSIS INRATHIPPOCAMPALNEURONSATAPPLICATIONOFPHOSPHATASE INHIBITOR FK506. AKAK_RATERASHIMA,MASAMICB NAKAI,TAKESHI HASHIMOTO,TAIZOU T&NIGUCHI,TOSH_IQ_KAWAMATA, KIYOSHI MAEDAAND CHIKAKO TANAKA,aoqo Institute for Aging Brain
and Cognitive
Disorders,
Himeji,67O,Japan.
The effect of FK506, an inhibitor of calcineurin, was examined in rat hippocampal CA1 neurons. 2-4 weeks old Wister rats were used to record the membrane current in hippocampal CA1 neurons with the brain slice patch clamp techniques. The samemembrane currents were recorded in hippocampal neurons in primary culture prepared from fetal Wister rats. The cell-attached patch and inside-out patch clamp techniques were used to record the current. The open of channels, whose conductancewere about40pS and 5OpS, was observed attheextracellurer application of 100pMNMDA. When 10nMFK506 was applied The same to the neurons, the mean open time became about three times as long as before. prolongation
119
of
the mean open time
Differential in the optic
localization lobe and
Osamu Shouno"3, Tadashi Kimura2'3, I Department of Biophysics, Faculty 'Institute of Biological Sciences, 3Electrotech Lab., Tsukuba, Ibaraki
the
occurred
of the stellate
two
at application
putative ganglion
of
of cyclosporin
A.
sodium channel a-subunits the squid Loligo breekeri.
Kiyonori Hirota3, Chikara SatoX of Science, Kyoto University, University of Tsukuba, Tsukuba, 305, Japan
and Gen Matsumotoj Kyoto 606, Japan Ibaraki 305, Japan
In the squid nervous tissues, the ~RNAS of two putative sodium channel a-subunits (GFLNl and SQSCl) were expressed. We raised two anti-peptide antibodies directed against GFLNland SQSCl-specific sequences (Ab,,l and Ab,*,, respectively). These anti-peptide antibodies were used in immunohistochemical experiments to examine the localization of two putative sodium channels in the optic lobe and the stellate ganglion of the squid Loligo breekeri. In the optic lobe, the neuropil of the medulla was heavily stained with AbsQl, and the radial columns composed of cell bodies of neurons were observed as a region of the relatively low immunoreactivity. In contrast, Ab,,: primarily stained the radial columns. In the stellate ganglion, cell bodies and fibers of giant fiber lobe neurons were immunoreactive with AbsQ,, whereas Ab,,l stained only cell bodies. .These findings suggest differential localization of two putative sodium channels within individual neurons.
120
SUPPRESSIVE EFFECTS OF PHENYTOIN AND CARBAMAZEPINE ON DEPOLARIZING AFTERPOTENTIAL IN PYRAMIDAL CELLS. TAKASHI OKADA. YOUNGNAM KANG, HARUNORI OHh4ORI. Dept. ofPhgsio1.. Kyoto Univ. Fat. ofMed.. Kyoto. 606. Jaoan. We report herethe ionic mechanismunderlying largeand long-lastingdepolarizingafterpotentials@AP)in relationwith the mechanism of epileptiformburst generationin neocorticalpyramidalcells. Injectionsof depolarizingcurrentpulsesunder whole-cellcurrentclampwith a CsCl-basedinternalmediummademostpyramidalcellsto generatesingleactionpotentials with a plateauphasefollowed by a largeand long-lastingDAP. When [K+10wasincreasedfrom 3 to 6 mM, the DAP onset potentialafter the first spikewas consistentlyelevatedfrom the control level of -52 * 4 mV to -43 + 5 mV recordedin the samecells(n=l8 cells). The elevatedlevel wasusually morepositivethanthethreshold for spikes,andresultedin a generationof burst. Individual spikesfollowing the first onewere triggeredfrom their precedingenhancedDAPs. DAP was producedby activationof CP+-dependentcationiccurrentwith slow-deactivationkinetics,which is morelikely carriedby K+ andCs+thanbyNa+. Ananti-epilepticdrug, phenytoin, suppressed DAPby blockingthe cationiccurrentwhile enhancingCa2+spikes. Carbamazepine appearedto suppressthe latephaseof DAP DAP may play a crucialrole in controllingthe excitability of pyramidalcellsandmay be involved in the epileptogenesis.
SINGLE CHANNELANALYSIS INRATHIPPOCAMPALNEURONSATAPPLICATIONOFPHOSPHATASE INHIBITOR FK506. AKAK_RATERASHIMA,MASAMICB NAKAI,TAKESHI HASHIMOTO,TAIZOU T&NIGUCHI,TOSH_IQ_KAWAMATA, KIYOSHI MAEDAAND CHIKAKO TANAKA,aoqo Institute for Aging Brain
and Cognitive
Disorders,
Himeji,67O,Japan.
The effect of FK506, an inhibitor of calcineurin, was examined in rat hippocampal CA1 neurons. 2-4 weeks old Wister rats were used to record the membrane current in hippocampal CA1 neurons with the brain slice patch clamp techniques. The samemembrane currents were recorded in hippocampal neurons in primary culture prepared from fetal Wister rats. The cell-attached patch and inside-out patch clamp techniques were used to record the current. The open of channels, whose conductancewere about40pS and 5OpS, was observed attheextracellurer application of 100pMNMDA. When 10nMFK506 was applied The same to the neurons, the mean open time became about three times as long as before. prolongation
119
of
the mean open time
Differential in the optic
localization lobe and
Osamu Shouno"3, Tadashi Kimura2'3, I Department of Biophysics, Faculty 'Institute of Biological Sciences, 3Electrotech Lab., Tsukuba, Ibaraki
the
occurred
of the stellate
two
at application
putative ganglion
of
of cyclosporin
A.
sodium channel a-subunits the squid Loligo breekeri.
Kiyonori Hirota3, Chikara SatoX of Science, Kyoto University, University of Tsukuba, Tsukuba, 305, Japan
and Gen Matsumotoj Kyoto 606, Japan Ibaraki 305, Japan
In the squid nervous tissues, the ~RNAS of two putative sodium channel a-subunits (GFLNl and SQSCl) were expressed. We raised two anti-peptide antibodies directed against GFLNland SQSCl-specific sequences (Ab,,l and Ab,*,, respectively). These anti-peptide antibodies were used in immunohistochemical experiments to examine the localization of two putative sodium channels in the optic lobe and the stellate ganglion of the squid Loligo breekeri. In the optic lobe, the neuropil of the medulla was heavily stained with AbsQl, and the radial columns composed of cell bodies of neurons were observed as a region of the relatively low immunoreactivity. In contrast, Ab,,: primarily stained the radial columns. In the stellate ganglion, cell bodies and fibers of giant fiber lobe neurons were immunoreactive with AbsQ,, whereas Ab,,l stained only cell bodies. .These findings suggest differential localization of two putative sodium channels within individual neurons.
120
SUPPRESSIVE EFFECTS OF PHENYTOIN AND CARBAMAZEPINE ON DEPOLARIZING AFTERPOTENTIAL IN PYRAMIDAL CELLS. TAKASHI OKADA. YOUNGNAM KANG, HARUNORI OHh4ORI. Dept. ofPhgsio1.. Kyoto Univ. Fat. ofMed.. Kyoto. 606. Jaoan. We report herethe ionic mechanismunderlying largeand long-lastingdepolarizingafterpotentials@AP)in relationwith the mechanism of epileptiformburst generationin neocorticalpyramidalcells. Injectionsof depolarizingcurrentpulsesunder whole-cellcurrentclampwith a CsCl-basedinternalmediummademostpyramidalcellsto generatesingleactionpotentials with a plateauphasefollowed by a largeand long-lastingDAP. When [K+10wasincreasedfrom 3 to 6 mM, the DAP onset potentialafter the first spikewas consistentlyelevatedfrom the control level of -52 * 4 mV to -43 + 5 mV recordedin the samecells(n=l8 cells). The elevatedlevel wasusually morepositivethanthethreshold for spikes,andresultedin a generationof burst. Individual spikesfollowing the first onewere triggeredfrom their precedingenhancedDAPs. DAP was producedby activationof CP+-dependentcationiccurrentwith slow-deactivationkinetics,which is morelikely carriedby K+ andCs+thanbyNa+. Ananti-epilepticdrug, phenytoin, suppressed DAPby blockingthe cationiccurrentwhile enhancingCa2+spikes. Carbamazepine appearedto suppressthe latephaseof DAP DAP may play a crucialrole in controllingthe excitability of pyramidalcellsandmay be involved in the epileptogenesis.