Biomaterial Database

Electrotonic profiles of interneurons in stratum pyramidale of the CA1 region of rat hippocampus. 1994

D Thurbon, and A Field, and S Redman

Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra.

1. Whole-cell recordings have been made from interneurons located in stratum pyramidale in the CA1 region of the hippocampus. The responses of these interneurons to brief current pulses were recorded; the neurons were filled with biocytin and their morphology was reconstructed. 2. The interneurons were identified as basket cells on the basis of the regional distribution of their axon collateral network and their location in stratum pyramidale. 3. A compartmental model of the reconstructed neuron was made, and the specific membrane resistivity (Rm), specific cytoplasmic resistivity (Ri), and somatic shunt leakage resistance (Rs) determined by adjusting these parameters until an optimal fit was obtained between the compartmental model's current pulse response and the recorded current pulse response of the neuron. 4. This procedure was successful for six neurons, giving Rm from 7 to 66 k omega cm2, Ri from 52 to 484 omega cm, and Rs from 84 M omega to infinity. The specific membrane capacitance was assumed to be 1 microF/cm2. The electrotonic length of the apical dendrites was 1.06 +/- 0.4, and for the basal dendrites it was 0.51 +/- 0.26 (mean +/- SD). 5. Although the total surface area of the interneurons and the physical length of their dendrites was much smaller than for CA1 pyramidal neurons, their electrotonic profiles were similar. Neurons with small physical profiles cannot be assumed to be more electrotonically compact than larger neurons, especially if the dendrites of the smaller neurons have a proportional reduction in diameter. 6. Two neurons did not require a somatic leakage conductance in their electrical representation. This suggests that when a somatic leakage conductance is required, it is an artifact resulting from electrode damage, rather than a requirement caused by a lower resistivity of the somatic membrane compared with the dendritic membrane. 7. Simulations of synaptic currents evoked in the dendrites of these interneurons while the soma is voltage clamped indicate large errors will occur in the time course measurements and amplitude of these currents. Also the ratio of N-methyl-D-aspartate:alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (NMDA:AMPA) currents at these synapses calculated from currents recorded at the soma will be in error because of the differential attenuation of the faster AMPA currents compared with the NMDA currents.

UI	MeSH Term	Description	Entries
D007395	Interneurons	Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions.	Intercalated Neurons,Intercalated Neuron,Interneuron,Neuron, Intercalated,Neurons, Intercalated
D008297	Male		Males
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
D009415	Nerve Net	A meshlike structure composed of interconnecting nerve cells that are separated at the synaptic junction or joined to one another by cytoplasmic processes. In invertebrates, for example, the nerve net allows nerve impulses to spread over a wide area of the net because synapses can pass information in any direction.	Neural Networks (Anatomic),Nerve Nets,Net, Nerve,Nets, Nerve,Network, Neural (Anatomic),Networks, Neural (Anatomic),Neural Network (Anatomic)
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
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011712	Pyramidal Tracts	Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts.	Corticobulbar Tracts,Corticospinal Tracts,Decussation, Pyramidal,Corticobulbar Tract,Corticospinal Tract,Pyramidal Decussation,Pyramidal Tract,Tract, Corticobulbar,Tract, Corticospinal,Tract, Pyramidal,Tracts, Corticobulbar,Tracts, Corticospinal,Tracts, Pyramidal
D001931	Brain Mapping	Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.	Brain Electrical Activity Mapping,Functional Cerebral Localization,Topographic Brain Mapping,Brain Mapping, Topographic,Functional Cerebral Localizations,Mapping, Brain,Mapping, Topographic Brain
D005260	Female		Females
D006624	Hippocampus	A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.	Ammon Horn,Cornu Ammonis,Hippocampal Formation,Subiculum,Ammon's Horn,Hippocampus Proper,Ammons Horn,Formation, Hippocampal,Formations, Hippocampal,Hippocampal Formations,Hippocampus Propers,Horn, Ammon,Horn, Ammon's,Proper, Hippocampus,Propers, Hippocampus,Subiculums