Biomaterial Database

Current-source density analysis in the rat olfactory bulb: laminar distribution of kainate/AMPA- and NMDA-receptor-mediated currents. 1999

V Aroniadou-Anderjaska, and M Ennis, and M T Shipley

Department of Anatomy and Neurobiology and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.

The one-dimensional current-source density method was used to analyze laminar field potential profiles evoked in rat olfactory bulb slices by stimulation in the olfactory nerve (ON) layer or mitral cell layer (MCL) and to identify the field potential generators and the characteristics of synaptic activity in this network. Single pulses to the ON evoked a prolonged (>/=400 ms) sink (S1ON) in the glomerular layer (GL) with corresponding sources in the external plexiform layer (EPL) and MCL and a relatively brief sink (S2ON) in the EPL, reversing in the internal plexiform and granule cell layers. These sink/source distributions suggested that S1ON and S2ON were generated in the apical dendrites of mitral/tufted cells and granule cells, respectively. The kainate/AMPA-receptor antagonist CNQX (10 microM) reduced the early phase of S1ON, blocked S2ON, and revealed a low amplitude, prolonged sink at the location of S2ON in the EPL. Reduction of Mg2+, in CNQX, enhanced both the CNQX-resistant component of S1ON and the EPL sink. This EPL sink reversed below the MCL, suggesting it was produced in granule cells. The NMDA-receptor antagonist APV (50 microM) reversibly blocked the CNQX-resistant field potentials in all layers. Single pulses were applied to the MCL to antidromically depolarize the dendrites of mitral/tufted cells. In addition to synaptic currents of granule cells, a low-amplitude, prolonged sink (S1mcl) was evoked in the GL. Corresponding sources were in the EPL, suggesting that S1mcl was generated in the glomerular dendritic tufts of mitral/tufted cells. Both S1mcl and the granule cell currents were nearly blocked by CNQX (10 microM) but enhanced by subsequent reduction of Mg2+; these currents were blocked by APV. S1mcl also was enhanced by gamma-aminobutyric acid-A-receptor antagonists applied to standard medium; this enhancement was reduced by APV. ON activation produces prolonged excitation in the apical dendrites of mitral/tufted cells, via kainate/AMPA and NMDA receptors, providing the opportunity for modulation and integration of sensory information at the first level of synaptic processing in the olfactory system. Granule cells respond to input from the lateral dendrites of mitral/tufted cells via both kainate/AMPA and NMDA receptors; however, in physiological concentrations of extracellular Mg2+, NMDA-receptor activation does not contribute significantly to the granule cell responses. The glomerular sink evoked by antidromic depolarization of mitral/tufted cell dendrites suggests that glutamate released from the apical dendrites of mitral/tufted cells may excite the same or neighboring mitral/tufted cell dendrites.

UI	MeSH Term	Description	Entries
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
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
D009830	Olfactory Bulb	Ovoid body resting on the CRIBRIFORM PLATE of the ethmoid bone where the OLFACTORY NERVE terminates. The olfactory bulb contains several types of nerve cells including the mitral cells, on whose DENDRITES the olfactory nerve synapses, forming the olfactory glomeruli. The accessory olfactory bulb, which receives the projection from the VOMERONASAL ORGAN via the vomeronasal nerve, is also included here.	Accessory Olfactory Bulb,Olfactory Tract,Bulbus Olfactorius,Lateral Olfactory Tract,Main Olfactory Bulb,Olfactory Glomerulus,Accessory Olfactory Bulbs,Bulb, Accessory Olfactory,Bulb, Main Olfactory,Bulb, Olfactory,Bulbs, Accessory Olfactory,Bulbs, Main Olfactory,Bulbs, Olfactory,Glomerulus, Olfactory,Lateral Olfactory Tracts,Main Olfactory Bulbs,Olfactorius, Bulbus,Olfactory Bulb, Accessory,Olfactory Bulb, Main,Olfactory Bulbs,Olfactory Bulbs, Accessory,Olfactory Bulbs, Main,Olfactory Tract, Lateral,Olfactory Tracts,Olfactory Tracts, Lateral,Tract, Lateral Olfactory,Tract, Olfactory,Tracts, Lateral Olfactory,Tracts, Olfactory
D003712	Dendrites	Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.	Dendrite
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D000465	Algorithms	A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.	Algorithm
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
D016194	Receptors, N-Methyl-D-Aspartate	A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.	N-Methyl-D-Aspartate Receptor,N-Methyl-D-Aspartate Receptors,NMDA Receptor,NMDA Receptor-Ionophore Complex,NMDA Receptors,Receptors, NMDA,N-Methylaspartate Receptors,Receptors, N-Methylaspartate,N Methyl D Aspartate Receptor,N Methyl D Aspartate Receptors,N Methylaspartate Receptors,NMDA Receptor Ionophore Complex,Receptor, N-Methyl-D-Aspartate,Receptor, NMDA,Receptors, N Methyl D Aspartate,Receptors, N Methylaspartate
D017208	Rats, Wistar	A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.	Wistar Rat,Rat, Wistar,Wistar Rats