Biomaterial Database

Spontaneous GABAA receptor-mediated inhibitory currents in adult rat somatosensory cortex. 1996

P A Salin, and D A Prince

Department of Neurology and Neurological Sciences, Stanford University School of Medicine, California 94305-5300, USA.

1. Spontaneous inhibitory synaptic currents (sIPSCs) were studied with whole cell voltage-clamp recordings from 131 pyramidal cells in adult rat somatosensory cortical slices. Neurons were intracellulary labeled with biocytin and classified as supragranular (SG, layers 2-3), layer IV (IV), or infragranular (IG, layer V) on the basis of the laminar localization of their somata. Somatic areas were similar for SG, IV, and IG neurons. All identified pyramidal cells generated high-frequency gamma-aminobutyric acid (GABAA) receptor-mediated synaptic events. 2. Bath application of bicuculline blocked the sIPSCs and resulted in a decrease of approximately 0.5 nS in resting conductance and an inward shift in baseline current. 3. sIPSC frequency was significantly lower in SG versus IG or IV neurons, and this difference was accounted for by the occurrence of a higher percentage of bursts of sIPSCs in the IG and IV neurons. 4. Bath application of the alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) decreased the frequency of sIPSCs by 13-21%. By contrast, application of the N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphonovaleric acid (D-AP5) generally had no effect on spontaneous IPSC frequency, suggesting that AMPA rather than NMDA receptor activation contributed to resting discharge of inhibitory interneurons. 5. Addition of tetrodotoxin (TTX) to the perfusion medium reduced the spontaneous IPSC frequency by approximately 30-55%. The miniature IPSCs (mIPSCs) seen in TTX-containing solutions had a frequency of approximately 10 Hz and an average conductance of 0.42-0.48 nS. 6. The kinetic properties of mIPSCs generated in pyramidal cells of different layers were the same, with the rise times of approximately 0.9 ms and decay time constants of approximately 8 ms at a holding potential of 0 mV. The decay phase of mIPSCs was generally fitted by one exponential and displayed a voltage dependence with an e-fold increase in decay time constant for a every 198-mV depolarization. 7. These results show that there is ongoing spontaneous release of GABA in neocortical slices that gives rise to high-frequency impulse-related and non-impulse-related postsynaptic inhibitory currents. Activation of AMPA receptors on inhibitory interneurons accounts for only a small proportion of the GABAA receptor-mediated events. Judging from the distribution of mIPSC frequencies in neurons of different laminae, there is a relatively uniform distribution of inhibitory synapses throughout the cortex. Tonic activation of GABAA receptors on neocortical pyramidal neurons generates an increase in resting membrane conductance that may play an important role in vivo by preventing the development of hyperexcitability, modulating excitatory synaptic events, and controlling the rate and patterns of spike discharge.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009433	Neural Inhibition	The function of opposing or restraining the excitation of neurons or their target excitable cells.	Inhibition, Neural
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
D011963	Receptors, GABA-A	Cell surface proteins which bind GAMMA-AMINOBUTYRIC ACID and contain an integral membrane chloride channel. Each receptor is assembled as a pentamer from a pool of at least 19 different possible subunits. The receptors belong to a superfamily that share a common CYSTEINE loop.	Benzodiazepine-Gaba Receptors,GABA-A Receptors,Receptors, Benzodiazepine,Receptors, Benzodiazepine-GABA,Receptors, Diazepam,Receptors, GABA-Benzodiazepine,Receptors, Muscimol,Benzodiazepine Receptor,Benzodiazepine Receptors,Benzodiazepine-GABA Receptor,Diazepam Receptor,Diazepam Receptors,GABA(A) Receptor,GABA-A Receptor,GABA-A Receptor alpha Subunit,GABA-A Receptor beta Subunit,GABA-A Receptor delta Subunit,GABA-A Receptor epsilon Subunit,GABA-A Receptor gamma Subunit,GABA-A Receptor rho Subunit,GABA-Benzodiazepine Receptor,GABA-Benzodiazepine Receptors,Muscimol Receptor,Muscimol Receptors,delta Subunit, GABA-A Receptor,epsilon Subunit, GABA-A Receptor,gamma-Aminobutyric Acid Subtype A Receptors,Benzodiazepine GABA Receptor,Benzodiazepine Gaba Receptors,GABA A Receptor,GABA A Receptor alpha Subunit,GABA A Receptor beta Subunit,GABA A Receptor delta Subunit,GABA A Receptor epsilon Subunit,GABA A Receptor gamma Subunit,GABA A Receptor rho Subunit,GABA A Receptors,GABA Benzodiazepine Receptor,GABA Benzodiazepine Receptors,Receptor, Benzodiazepine,Receptor, Benzodiazepine-GABA,Receptor, Diazepam,Receptor, GABA-A,Receptor, GABA-Benzodiazepine,Receptor, Muscimol,Receptors, Benzodiazepine GABA,Receptors, GABA A,Receptors, GABA Benzodiazepine,delta Subunit, GABA A Receptor,epsilon Subunit, GABA A Receptor,gamma Aminobutyric Acid Subtype A Receptors
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D005073	Evoked Potentials, Somatosensory	The electric response evoked in the CEREBRAL CORTEX by stimulation along AFFERENT PATHWAYS from PERIPHERAL NERVES to CEREBRUM.	Somatosensory Evoked Potentials,Evoked Potential, Somatosensory,Somatosensory Evoked Potential
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
D013003	Somatosensory Cortex	Area of the parietal lobe concerned with receiving sensations such as movement, pain, pressure, position, temperature, touch, and vibration. It lies posterior to the central sulcus.	Brodmann Area 1,Brodmann Area 2,Brodmann Area 3,Brodmann Areas 1, 2, 3,Brodmann Areas 1, 2, and 3,Brodmann Areas 3, 1, 2,Brodmann Areas 3, 1, and 2,Brodmann's Area 1,Brodmann's Area 2,Brodmann's Area 3,Brodmann's Areas 1, 2, and 3,Brodmann's Areas 3, 1, and 2,Parietal-Opercular Cortex,Primary Somesthetic Area,S1 Cortex,S2 Cortex,SII Cortex,Anterior Parietal Cortex,Gyrus Postcentralis,Post Central Gyrus,Postcentral Gyrus,Primary Somatic Sensory Area,Primary Somatosensory Area,Primary Somatosensory Areas,Primary Somatosensory Cortex,SI Cortex,Second Somatic Sensory Area,Secondary Sensory Cortex,Secondary Somatosensory Area,Secondary Somatosensory Cortex,Area 1, Brodmann,Area 1, Brodmann's,Area 2, Brodmann,Area 2, Brodmann's,Area 3, Brodmann,Area 3, Brodmann's,Area, Primary Somatosensory,Area, Primary Somesthetic,Area, Secondary Somatosensory,Areas, Primary Somatosensory,Brodmanns Area 1,Brodmanns Area 2,Brodmanns Area 3,Cortex, Anterior Parietal,Cortex, Parietal-Opercular,Cortex, Primary Somatosensory,Cortex, S1,Cortex, S2,Cortex, SI,Cortex, SII,Cortex, Secondary Sensory,Cortex, Secondary Somatosensory,Cortex, Somatosensory,Gyrus, Post Central,Gyrus, Postcentral,Parietal Cortex, Anterior,Parietal Opercular Cortex,Parietal-Opercular Cortices,Primary Somatosensory Cortices,Primary Somesthetic Areas,S1 Cortices,S2 Cortices,SII Cortices,Secondary Somatosensory Areas,Sensory Cortex, Secondary,Somatosensory Area, Primary,Somatosensory Area, Secondary,Somatosensory Areas, Primary,Somatosensory Cortex, Primary,Somatosensory Cortex, Secondary,Somesthetic Area, Primary,Somesthetic Areas, Primary
D017207	Rats, Sprague-Dawley	A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.	Holtzman Rat,Rats, Holtzman,Sprague-Dawley Rat,Rats, Sprague Dawley,Holtzman Rats,Rat, Holtzman,Rat, Sprague-Dawley,Sprague Dawley Rat,Sprague Dawley Rats,Sprague-Dawley Rats