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The fast IPSP in sympathetic preganglionic neurons (SPN)
S106
SYNAPTIC RESPONSES OF PARS COMPACTA NEURONS OF THE RAT SUBSTANTIA NIGRA IN THE SLICE PREPARATION STUDIED WITH WHOLE-CELL VOLTAGE CLAMP RECORDING. SI-YOUNG SONG* and SHIRO KONISHI. Laboratory of Cellular Physiology, Mitsubishi Kasei Institute of Life Sciences. 11 Minamiooya. Machida-shi. Tokyo 194, Japan. Whole-cell voltage clamp recording was applied to midbrain slices to characterize properties of synaptic inputs to pars compacta neurons in the substantia nigra (SN). Transverse slices of the midbrain were cut from 5-IO-day old rats, placed on a chamber attached to a microscope stage, and continuously The pars compacta neurons were visually identified under perfused with artificial cerebrospinal fluid. Nomarskl optics. When recorded with patch pipettes containing 140 mM KCI, SN neuronsexhibited three
distinct spontaneous synaptic currents at a holding potential of -50 mV: two typesof inwardcurrents and the inwardcurrents one outwardcurrentwith fluctuating amplitudes.With respectto the time course, responses with a mean half-decay time of 4 and 15 msec, were distinguished intofastand slow synaptic The fast synaptic response was suppressed by kynurenic acid (2 mM). The slow response respectively. was blocked by bicucuiline (5 uM) and augmented by diazepam (30 uM). Application of GABA (30-199 uM) The observations suggest that GABA is involved as a produced an inward current in most ceils. Both tetrodotoxln (0.2 uM)-sensitive and neurotransmitter to mediate the slow inward synaptic current. -insensitive slow synaptic responses were observed, which suggests that synaptic inputs are derived from Application of serotonin (20-100 uM1 markedly GABA neurons intrinsic as well as extrinsic to the SN. increased the frequency and mean amplitude of the GABA-medlated synaptic response in some ceils. The results suggest that serotonergic neurons projecting to the SN modulate the activity of GABA synapses on pars compacta neurons by a presynaptic mechanism.
CONTRIBUI’ION OF NON-WA AND NMDAREEPTORS To
EXCTIA'RJRY SYNAFfIC TRANSHISSION IN THF. RAT VISUALCORTEX,
AYAHIKONISHIGORI*FLMITAKAKIMURA*AND TADAHARUTSUM3I0, Department of y-p-Research Center, Osaka University Medical School, Kita-ku, Osaka, -530 Japan. Actions visual
of
cortex
Antagonists
excitatory
respectively. mre
of
contrast,
the
suppressed
recordings
of the monosynaptic or slightly
slope
slope
and amplitude
in mediating
all
the cells
excitatory
cells
in
layer
II/III
in slice
(APV) and 6-cyano-7-nitroquinoxaline-2, (NMDA)and the non-MA
was demonstrated
responses
of
of
white matter were studied
that responses
Biomedical of
were resistant
postsynaptic
from 22 neurons.
changed by APV although
polysynaptic tested. synaptic
EPSPs were It
inputs
is
rat
3-dione
(CNQX),
types of ELMreceptors,
of almost
all
the cells
were
inputs:
to APV while about 80 % of the polysynaptic
to APV. Excitatory intracellularly
the
preparations.
to APV depended to some degree on the types of synaptic
sensitive
was not significantly
F.PSPs in almost
degree,
it
sensitivity
the white matter were recorded
EF’SPs, the rising
on responses
VI and the underlying
for the N-methyl-L!-aspartate
In extracellular
were sensitive
stimulation
varying
antagonists
by CNQX. In contrast,
than one half
responses
(FAA) antagonists
of layer
used were Z-amino-sphosphonovalerate
which are selective suppressed
amino acid
to stimulation
Neurophysiology,
that
II/III
(EPSPs) evoked by
In most of
the amplitude
mostly
suggested to layer
potentials
reduced
the monosynaptic
was slightly
reduced.
In
by APV. CNQX completely
NMA receptors neurons mostly
participate, from other
to
a
cortical
neurons.
THE FAST IPSP IN SYMPATHETIC PREGANGLIONIC NEURONS (SPN). HIROE INOKUCHIl, MEGUMU YOSHIMURA1 , SYOGORO HISHI' , CAN10 POLOSA"' , AND ANDRZEJ TRZHHSKI*3 , ‘Dept. Physiol., Kurume Univ. Sch. Med., Kurume 830, Japan, 2McGill Univ. and 3Warsaw Med. Acad. The fast IPSP in the SPN of the intermediolateral (IML) nucleus in tissue slices of cat thoracic spinal cord was studied with intracellular recording Focal stimulation of the IML methods using K-citrate-filled microelectrodes. region evoked a mixture of the fast EPSP and fast IPSP. Elimination of the fast EPSP with CNQX (20 !.IM) and APV (40-100 uM) left the fast IPSP alone. The IPSP was reversed in polarity at approximately -70 mV, and so were the GAHA- and glycineinduced responses. The IPSP equilibrium potential was dependent on the external Cl concentration in a manner predictable from the Nernst equation. The fast IPSP was abolished by strychnine (2 uM) in 60% of neurons examined, by bicuculline (30 nMM) in 30%, and by strychnine plus bicuculline in 10%. when pairs of the fast IPSP were elicited, the amplitude of the second IPSP was augmented for a period of 200 to 300 ms after the first IPSP. This facilitation phase was not followed by a phase of depression. Responses induced by exogenously applied glycine or GAHA did not show either facilitation or depression. The results suggest that the fast IPSP is due to a selective increase in Cl conductance that is mediated by glycine and/or GAHA. The fast IPSP is followed by a phase of facilitation that is presynaptic in origin.
SYNAPTIC RESPONSES OF PARS COMPACTA NEURONS OF THE RAT SUBSTANTIA NIGRA IN THE SLICE PREPARATION STUDIED WITH WHOLE-CELL VOLTAGE CLAMP RECORDING. SI-YOUNG SONG* and SHIRO KONISHI. Laboratory of Cellular Physiology, Mitsubishi Kasei Institute of Life Sciences. 11 Minamiooya. Machida-shi. Tokyo 194, Japan. Whole-cell voltage clamp recording was applied to midbrain slices to characterize properties of synaptic inputs to pars compacta neurons in the substantia nigra (SN). Transverse slices of the midbrain were cut from 5-IO-day old rats, placed on a chamber attached to a microscope stage, and continuously The pars compacta neurons were visually identified under perfused with artificial cerebrospinal fluid. Nomarskl optics. When recorded with patch pipettes containing 140 mM KCI, SN neuronsexhibited three
distinct spontaneous synaptic currents at a holding potential of -50 mV: two typesof inwardcurrents and the inwardcurrents one outwardcurrentwith fluctuating amplitudes.With respectto the time course, responses with a mean half-decay time of 4 and 15 msec, were distinguished intofastand slow synaptic The fast synaptic response was suppressed by kynurenic acid (2 mM). The slow response respectively. was blocked by bicucuiline (5 uM) and augmented by diazepam (30 uM). Application of GABA (30-199 uM) The observations suggest that GABA is involved as a produced an inward current in most ceils. Both tetrodotoxln (0.2 uM)-sensitive and neurotransmitter to mediate the slow inward synaptic current. -insensitive slow synaptic responses were observed, which suggests that synaptic inputs are derived from Application of serotonin (20-100 uM1 markedly GABA neurons intrinsic as well as extrinsic to the SN. increased the frequency and mean amplitude of the GABA-medlated synaptic response in some ceils. The results suggest that serotonergic neurons projecting to the SN modulate the activity of GABA synapses on pars compacta neurons by a presynaptic mechanism.
CONTRIBUI’ION OF NON-WA AND NMDAREEPTORS To
EXCTIA'RJRY SYNAFfIC TRANSHISSION IN THF. RAT VISUALCORTEX,
AYAHIKONISHIGORI*FLMITAKAKIMURA*AND TADAHARUTSUM3I0, Department of y-p-Research Center, Osaka University Medical School, Kita-ku, Osaka, -530 Japan. Actions visual
of
cortex
Antagonists
excitatory
respectively. mre
of
contrast,
the
suppressed
recordings
of the monosynaptic or slightly
slope
slope
and amplitude
in mediating
all
the cells
excitatory
cells
in
layer
II/III
in slice
(APV) and 6-cyano-7-nitroquinoxaline-2, (NMDA)and the non-MA
was demonstrated
responses
of
of
white matter were studied
that responses
Biomedical of
were resistant
postsynaptic
from 22 neurons.
changed by APV although
polysynaptic tested. synaptic
EPSPs were It
inputs
is
rat
3-dione
(CNQX),
types of ELMreceptors,
of almost
all
the cells
were
inputs:
to APV while about 80 % of the polysynaptic
to APV. Excitatory intracellularly
the
preparations.
to APV depended to some degree on the types of synaptic
sensitive
was not significantly
F.PSPs in almost
degree,
it
sensitivity
the white matter were recorded
EF’SPs, the rising
on responses
VI and the underlying
for the N-methyl-L!-aspartate
In extracellular
were sensitive
stimulation
varying
antagonists
by CNQX. In contrast,
than one half
responses
(FAA) antagonists
of layer
used were Z-amino-sphosphonovalerate
which are selective suppressed
amino acid
to stimulation
Neurophysiology,
that
II/III
(EPSPs) evoked by
In most of
the amplitude
mostly
suggested to layer
potentials
reduced
the monosynaptic
was slightly
reduced.
In
by APV. CNQX completely
NMA receptors neurons mostly
participate, from other
to
a
cortical
neurons.
THE FAST IPSP IN SYMPATHETIC PREGANGLIONIC NEURONS (SPN). HIROE INOKUCHIl, MEGUMU YOSHIMURA1 , SYOGORO HISHI' , CAN10 POLOSA"' , AND ANDRZEJ TRZHHSKI*3 , ‘Dept. Physiol., Kurume Univ. Sch. Med., Kurume 830, Japan, 2McGill Univ. and 3Warsaw Med. Acad. The fast IPSP in the SPN of the intermediolateral (IML) nucleus in tissue slices of cat thoracic spinal cord was studied with intracellular recording Focal stimulation of the IML methods using K-citrate-filled microelectrodes. region evoked a mixture of the fast EPSP and fast IPSP. Elimination of the fast EPSP with CNQX (20 !.IM) and APV (40-100 uM) left the fast IPSP alone. The IPSP was reversed in polarity at approximately -70 mV, and so were the GAHA- and glycineinduced responses. The IPSP equilibrium potential was dependent on the external Cl concentration in a manner predictable from the Nernst equation. The fast IPSP was abolished by strychnine (2 uM) in 60% of neurons examined, by bicuculline (30 nMM) in 30%, and by strychnine plus bicuculline in 10%. when pairs of the fast IPSP were elicited, the amplitude of the second IPSP was augmented for a period of 200 to 300 ms after the first IPSP. This facilitation phase was not followed by a phase of depression. Responses induced by exogenously applied glycine or GAHA did not show either facilitation or depression. The results suggest that the fast IPSP is due to a selective increase in Cl conductance that is mediated by glycine and/or GAHA. The fast IPSP is followed by a phase of facilitation that is presynaptic in origin.