scholarly journals Locus Ceruleus Activation Initiates Delayed Synaptic Potentiation of Perforant Path Input to the Dentate Gyrus in Awake Rats: A Novel  -Adrenergic- and Protein Synthesis-Dependent Mammalian Plasticity Mechanism

2004 ◽  
Vol 24 (3) ◽  
pp. 598-604 ◽  
Author(s):  
S. G. Walling
Keyword(s):  
Protein Synthesis ◽  
Dentate Gyrus ◽  
Locus Ceruleus ◽  
Perforant Path ◽  
Synaptic Potentiation ◽  
Plasticity Mechanism ◽  
Awake Rats

scholarly journals Phasic Boosting of Medial Perforant Path-Evoked Granule Cell Output Time-Locked to Spontaneous Dentate EEG Spikes in Awake Rats

1998 ◽  
Vol 79 (6) ◽  
pp. 2825-2832 ◽  
Author(s):  
Clive R. Bramham
Keyword(s):  
Dentate Gyrus ◽  
Slow Wave ◽  
Granule Cell ◽  
Slow Wave Sleep ◽  
Population Spike ◽  
Perforant Path ◽  
Evoked Responses ◽  
Population Spike Amplitude ◽  
Output Time ◽  
Awake Rats

Bramham, Clive R. Phasic boosting of medial perforant path-evoked granule cell output time-locked to spontaneous dentate EEG spikes in awake rats. J. Neurophysiol. 79: 2825–2832, 1998. Dentate spikes (DSs) are positive-going field potential transients that occur intermittently in the hilar region of the dentate gyrus during alert wakefulness and slow-wave sleep. The function of dentate spikes is unknown; they have been suggested to be triggered by perforant path input and are associated with firing of hilar interneurons and inhibition of CA3 pyramidal cells. Here we investigated the effect of DSs on medial perforant path (MPP)-granule cell-evoked transmission in freely moving rats. The MPP was stimulated selectively in the angular bundle while evoked field potentials and the EEG were recorded with a vertical multielectrode array in the dentate gyrus. DSs were identified readily on the basis of their characteristic voltage-versus–depth profile, amplitude, duration, and state dependency. Using on-line detection of the DS peak, the timing of MPP stimulation relative to single DSs was controlled. DS-triggered evoked responses were compared with conventional, manually evoked responses in still-alert wakefulness (awake immobility) and, in some cases, slow-wave sleep. Input-output curves were obtained with stimulation on the positive DS peak (0 delay) and at delays of 50, 100, and 500 ms. Stimulation on the peak DS was associated with a significant increase in the population spike amplitude, a reduction in population spike latency, and a decrease in the field excitatory postsynaptic potential (fEPSP) slope, relative to manual stimulation. Granule cell excitability was enhanced markedly during DSs, as indicated by a mean 93% increase in the population spike amplitude and a leftward shift in the fEPSP-spike relation. Maximum effects occurred at the DS peak, and lasted between 50 and 100 ms. Paired-pulse inhibition of the population spike was unaffected, indicating intact recurrent inhibition during DSs. The results demonstrate enhancement of perforant path-evoked granule cell output time-locked to DSs. DSs therefore may function to intermittently boost excitatory transmission in the entorhinal cortex-dentate gyrus-CA3 circuit. Such a mechanism may be important in the natural induction of long-term potentiation in the dentate gyrus and CA3 regions.

Increase in extracellular dopamine levels during clozapine-induced potentiation in the hippocampal dentate gyrus of chronically prepared rabbits

2008 ◽  
Vol 86 (5) ◽  
pp. 249-256 ◽  
Author(s):  
Takashi Kubota ◽  
Itsuki Jibiki ◽  
Akira Ishikawa ◽  
Tomomi Kawamura ◽  
Sonoko Kurokawa ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Nmda Receptor ◽  
Dentate Gyrus ◽  
Negative Symptoms ◽  
Clinical Effect ◽  
Perforant Path ◽  
Hippocampal Dentate Gyrus ◽  
Extracellular Dopamine ◽  
Stimulation Of ◽  
Synaptic Responses

We previously found that 20 mg/kg clozapine i.p. potentiated the excitatory synaptic responses elicited in the dentate gyrus by single electrical stimulation of the perforant path in chronically prepared rabbits. We called this phenomenon clozapine-induced potentiation and proved that it was an NMDA receptor-mediated event. This potentiation is presumably related to clozapine’s clinical effect on negative symptoms and cognitive dysfunctions in schizophrenia. In the present study, to investigate the mechanisms underlying clozapine-induced potentiation, we examined whether extracellular dopamine and 5-HT levels changed during the potentiation by using a microdialysis technique in the dentate gyrus. The extracellular concentrations of dopamine and 5-HT levels were measured every 5 min during all experiments. Extracellular 5-HT levels did not change, but dopamine levels eventually increased significantly during clozapine-induced potentiation. The increase in the dopamine levels occurred almost simultaneously with the induction of clozapine-induced potentiation. These results suggest that clozapine-induced potentiation is at least partly attributable to a dopamine-mediated potentiation of excitatory synaptic transmission. The present study implies that such phenomena occur also in the perforant path–dentate gyrus pathway.

Protein synthesis in the neuropil of the rat dentate gyrus during synapse development

1990 ◽  
Vol 26 (4) ◽  
pp. 474-482 ◽  
Author(s):  
L. L. Phillips ◽  
A. E. Pollack ◽  
O. Steward
Keyword(s):  
Protein Synthesis ◽  
Dentate Gyrus ◽  
Synapse Development

Presynaptic Group II mGluR Inhibition of Short-Term Depression in the Medial Perforant Path of the Dentate Gyrus In Vitro

2001 ◽  
Vol 85 (6) ◽  
pp. 2509-2515 ◽  
Author(s):  
John Kilbride ◽  
Anthony M. Rush ◽  
Michael J. Rowan ◽  
Roger Anwyl
Keyword(s):  
Dentate Gyrus ◽  
Metabotropic Glutamate Receptors ◽  
State Level ◽  
Perforant Path ◽  
Dependent Manner ◽  
Short Term ◽  
Concentration Dependent Manner ◽  
Postsynaptic Response ◽  
Group Ii

Inhibition of short-term plasticity by activation of presynaptic group II metabotropic glutamate receptors (group II mGluR) was investigated in the medial perforant path of the dentate gyrus in the hippocampus in vitro. Brief trains of stimulation (10 stimuli at 1–200 Hz) evoked short-term depression of field excitatory postsynaptic potentials (EPSPs). The steady-state level of depression, measured after 10 stimuli, was frequency dependent, increasing between 1 and 200 Hz. Activation of group II mGluR by the selective agonist LY354740 did not alter short-term depression evoked by frequencies up to 10 Hz, but did inhibit short-term depression evoked at higher frequencies in a frequency- and concentration-dependent manner. The time-averaged postsynaptic response (EPSP per unit time) was found to increase linearly with frequency up to ∼20 Hz. At higher frequencies, the response plateaued, thereby becoming independent of frequency. Frequencies above this were differentiated only during the transient postsynaptic response that accompanies changes in firing rates. Activation of presynaptically located group II mGluR increased the frequency at which the EPSP per unit time plateaued up to 30–50 Hz.

Spontaneous Waves in the Dentate Gyrus of Slices From the Ventral Hippocampus

2004 ◽  
Vol 92 (6) ◽  
pp. 3385-3398 ◽  
Author(s):  
Laura Lee Colgin ◽  
Don Kubota ◽  
Fernando A. Brucher ◽  
Yousheng Jia ◽  
Erin Branyan ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Dentate Gyrus ◽  
Granule Cell ◽  
Action Potentials ◽  
Slow Wave Sleep ◽  
Glutamate Release ◽  
Acetylcholinesterase Inhibitor ◽  
Granule Cell Layer ◽  
Perforant Path ◽  
The Waves

Spontaneous negative-going potentials occurring at an average frequency of 0.7 Hz were recorded from the dentate gyrus of slices prepared from the temporal hippocampus of young adult rats. These events (here termed “dentate waves”) in several respects resembled the dentate spikes described for freely moving rats during immobile behaviors and slow-wave sleep. Action potentials were observed on the descending portion of the in vitro waves and, as expected from this, whole cell recordings established that the waves were composed of depolarizing currents. Dentate waves appeared to be locally generated within the granule cell layer and were greatly reduced by antagonists of AMPA-type glutamate receptors or by lesions to the entorhinal cortex. Simultaneous recordings indicated that the waves were often synchronized in the inner and outer blades of the dentate gyrus. Knife cuts through the perforant path and the commissural/associational system did not eliminate synchronization, leaving electrotonic propagation via gap junctions as its probable cause. In accord with this, cuts that separated the two blades of the dentate eliminated synchronization between them, and a compound that inhibits gap junctions reduced wave activity. Dentate waves were regularly accompanied by sharp waves in field CA3 and were reduced in size by the acetylcholinesterase inhibitor, physostigmine. It is hypothesized that dentate waves occur when spontaneous glutamate release from dentate afferents produces action potentials in neighboring granule cells that then summate electrotonically into a population event; once initiated, the waves propagate, again electrotonically, and thereby engage a significant portion of the granule cell population.

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