Role of Calcium Conductances on Spike Afterpotentials in Rat Trigeminal Motoneurons

Kobayashi, Masayuki; Inoue, Tomio; Matsuo, Ryuji; Masuda, Yuji; Hidaka, Osamu; Kang, Youngnam; Morimoto, Toshifumi

doi:10.1152/jn.1997.77.6.3273

Cited by 59 publications

(56 citation statements)

References 51 publications

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“…3B). These afterpotentials play an important role in the regulation of repetitive spike firing (Schwindt et al, 1988;Kobayashi et al, 1997), and they were similar in control and post-status epilepticus rats (Table 1). Long (500 msec) depolarizing current pulses evoked slightly adapting trains, not bursts, of action potentials that were similar in control and post-status epilepticus rats (Fig.…”

Section: Normal Intrinsic Electrophysiological Properties Of Layer IImentioning

confidence: 75%

Reduced Inhibition and Increased Output of Layer II Neurons in the Medial Entorhinal Cortex in a Model of Temporal Lobe Epilepsy

2003

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Temporal lobe epilepsy is the most common type of epilepsy in adults, and its underlying mechanisms are unclear. To investigate how the medial entorhinal cortex might contribute to temporal lobe epilepsy, we evaluated the histology and electrophysiology of slices from rats 3-7 d after an epileptogenic injury (pilocarpine-induced status epilepticus). Nissl staining, NeuN immunocytochemistry, and in situ hybridization for GAD65 mRNA were used to verify the preferential loss of glutamatergic neurons and the relative sparing of GABAergic interneurons in layer III. From slices adjacent to those that were used for anatomy, we obtained whole-cell patch recordings from layer II medial entorhinal cortical neurons. Recordings under current-clamp conditions revealed similar intrinsic electrophysiological properties (resting membrane potential, input resistance, single spike, and repetitive firing properties) to those of controls. Spontaneous IPSCs were less frequent (68% of controls), smaller in amplitude (57%), and transferred less charge (51%) than in controls. However, the frequency, amplitude, and rise time of miniature IPSCs were normal. These findings suggest that after epileptogenic injuries the layer II entorhinal cortical neurons receive less GABA A receptor-mediated synaptic input because presynaptic inhibitory interneurons become less active. To investigate the possible consequences of reduced spontaneous inhibitory input to layer II neurons, we recorded field potentials in the dentate gyrus, their major synaptic target. At 5 d after pilocarpine-induced status epilepticus the spontaneous field potentials recorded in vivo were over three times more frequent than in controls. These findings suggest that an epileptogenic injury reduces inhibition of layer II neurons and results in excessive synaptic input to the dentate gyrus.

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Section: Normal Intrinsic Electrophysiological Properties Of Layer IImentioning

confidence: 75%

Reduced Inhibition and Increased Output of Layer II Neurons in the Medial Entorhinal Cortex in a Model of Temporal Lobe Epilepsy

2003

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“…They are the result of large (BK) and small conductance (SK) K + channels gated by a rise in intracellular Ca 2+ , and in the case of the BK channels, also by voltage (1065). Both I K Ca(BK) and I K Ca(SK) are present in motoneurons (205,463,523,647,666,667,826,870,918,919,1070,1213,1291,1311). I K Ca(BK) , which also is called I c , is selective for K + and activates after an influx of Ca 2+ during an action potential.…”

Section: Active Membrane Properties Of Motoneuronsmentioning

confidence: 99%

“…Spike afterhyperpolarization in motoneurons is blocked by inorganic Ca 2+ blockers, intracellular injection of Ca 2+ chelators, and notably by apamin (7,205,523,647,1311,1426), suggesting that motoneurons express SK channels and that they play a critical role in the repetitive firing behavior of motoneurons. In mouse motoneurons in culture, unitary currents from SK channels have a ~18-pS conductance, a 3.5-ms mean open time, and show no voltage dependency (825).…”

Section: Active Membrane Properties Of Motoneuronsmentioning

confidence: 99%

“…Ca 2+ conductances affect the falling phase of the action potential, spike afterdepolarization (ADP), and afterhyperpolarization (AHP), in the latter case via I K Ca (463,523,524,647,870,1291,1310,1311). The Ca 2+ channel subtypes underlying ADP, which is most prominent in neonatal animals, and AHP can be distinguished pharmacologically and result from both LVA and HVA as well as HVA Ca 2+ channels, respectively (647,1291,1311). The L-type Ca 2+ channels play a central role in some motoneurons that are capable of generating plateau potentials (521,527).…”

Section: Active Membrane Properties Of Motoneuronsmentioning

confidence: 99%

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Synaptic Control of Motoneuronal Excitability

Rekling

Funk

Bayliss

et al. 2000

Physiological Reviews

537

482

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Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre-and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre-and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K + current, cationic inward current, hyperpolarization-activated inward current, Ca 2+ channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior.

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“…In a similar manner, the ADP and AHP conductances were also found to exist in all four of the GnRH cell types but, interestingly, only in subpopulations of each. Calcium entry through N-type Ca 2ϩ channels has been proposed to underlie the AHP, whereas entry through P/Q-and T-type Ca 2ϩ channels is thought to be responsible for generation of ADP (Kobayashi et al, 1993;Sim and Allen, 1998). Together, these observations in native GnRH neurons indicate the existence of multiple layers of f unctional heterogeneity within the GnRH phenotype.…”

Section: Heterogeneity Within the Adult Gnrh Neuronal Populationmentioning

confidence: 99%

Heterogeneity in the Basic Membrane Properties of Postnatal Gonadotropin-Releasing Hormone Neurons in the Mouse

2001

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The electrophysiological characteristics of unmodified, postnatal gonadotropin-releasing hormone (GnRH) neurons in the female mouse were studied using whole-cell recordings and single-cell RT-PCR methodology. The GnRH neurons of adult animals fired action potentials and exhibited distinguishable voltage-current relationships in response to hyperpolarizing and depolarizing current injections. On the basis of their patterns of inward rectification, rebound depolarization, and ability to fire repetitively, GnRH neurons in intact adult females were categorized into four cell types (type I, 48%; type II, 36%; type III, 11%; type IV, 5%). The GnRH neurons of juvenile animals (15-22 d) exhibited passive membrane properties similar to those of adult GnRH neurons, although only type I (61%) and type II (7%) cells were encountered, in addition to a group of "silent-type" GnRH neurons (32%) that were unable to fire action potentials. A massive, action potential-independent tonic GABA input, signaling through the GABA A receptor, was present at all ages. Afterdepolarization and afterhyperpolarization potentials (AHPs) were observed after single action potentials in subpopulations of each GnRH neuron type. Tetrodotoxin (TTX)-independent calcium spikes, as well as AHPs, were encountered more frequently in juvenile GnRH neurons compared with adults. These observations demonstrate the existence of multiple layers of functional heterogeneity in the firing properties of GnRH neurons. Together with pharmacological experiments, these findings suggest that potassium and calcium channels are expressed in a differential manner within the GnRH phenotype. This heterogeneity occurs in a development-specific manner and may underlie the functional maturation and diversity of this unique neuronal phenotype.

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Role of Calcium Conductances on Spike Afterpotentials in Rat Trigeminal Motoneurons

Cited by 59 publications

References 51 publications

Reduced Inhibition and Increased Output of Layer II Neurons in the Medial Entorhinal Cortex in a Model of Temporal Lobe Epilepsy

Reduced Inhibition and Increased Output of Layer II Neurons in the Medial Entorhinal Cortex in a Model of Temporal Lobe Epilepsy

Synaptic Control of Motoneuronal Excitability

Heterogeneity in the Basic Membrane Properties of Postnatal Gonadotropin-Releasing Hormone Neurons in the Mouse

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