scholarly journals NMDA-Dependent Mechanisms Only Affect the BOLD Response in the Rat Dentate Gyrus by Modifying Local Signal Processing

2011 ◽  
Vol 32 (3) ◽  
pp. 570-584 ◽  
Author(s):  
Regina Tiede ◽  
Karla Krautwald ◽  
Anja Fincke ◽  
Frank Angenstein
Keyword(s):  
Signal Processing ◽  
Nmda Receptor ◽  
Dentate Gyrus ◽  
Entorhinal Cortex ◽  
Bold Response ◽  
Electrophysiological Response ◽  
Perforant Pathway ◽  
Bold Responses ◽  
The Right ◽  
Stimulation Of

The role of N-methyl-d-aspartate (NMDA) receptor-mediated mechanisms in the formation of a blood oxygen level-dependent (BOLD) response was studied using electrical stimulation of the right perforant pathway. Stimulation of this fiber bundle triggered BOLD responses in the right hippocampal formation and in the left entorhinal cortex. The perforant pathway projects to and activates the dentate gyrus monosynaptically, activation in the contralateral entorhinal cortex is multisynaptic and requires forwarding and processing of signals. Application of the NMDA receptor antagonist MK801 during stimulation had no effect on BOLD responses in the right dentate gyrus, but reduced the BOLD responses in the left entorhinal cortex. In contrast, application of MK801 before the first stimulation train reduced the BOLD response in both regions. Electrophysiological recordings revealed that the initial stimulation trains changed the local processing of the incoming signals in the dentate gyrus. This altered electrophysiological response was not further changed by a subsequent application of MK801, which is in agreement with an unchanged BOLD response. When MK801 was present during the first stimulation train, a dissimilar electrophysiological response pattern was observed and corresponds to an altered BOLD response, indicating that NMDA-dependent mechanisms indirectly affect the BOLD response, mainly via modifying local signal processing and subsequent propagation.

scholarly journals Low Frequency Stimulation of the Perforant Pathway Generates Anesthesia-Specific Variations in Neural Activity and BOLD Responses in the Rat Dentate Gyrus

2011 ◽  
Vol 32 (2) ◽  
pp. 291-305 ◽  
Author(s):  
Karla Krautwald ◽  
Frank Angenstein
Keyword(s):  
Dentate Gyrus ◽  
Stimulus Frequency ◽  
Low Frequency ◽  
Blood Oxygen Level Dependent ◽  
Bold Response ◽  
Blood Oxygen Level ◽  
Perforant Pathway ◽  
Bold Responses ◽  
Dependent Signal ◽  
Frequency Stimulation

To study how various anesthetics affect the relationship between stimulus frequency and generated functional magnetic resonance imaging (fMRI) signals in the rat dentate gyrus, the perforant pathway was electrically stimulated with repetitive low frequency (i.e., 0.625, 1.25, 2.5, 5, and 10 Hz) stimulation trains under isoflurane/N2O, isoflurane, medetomidine, and α-chloralose. During stimulation, the blood oxygen level-dependent signal intensity (BOLD response) and local field potentials in the dentate gyrus were simultaneously recorded to prove whether the present anesthetic controls the generation of a BOLD response via targeting general hemodynamic parameters, by affecting mechanisms of neurovascular coupling, or by disrupting local signal processing. Using this combined electrophysiological/fMRI approach, we found that the threshold frequency (i.e., the minimal frequency required to trigger significant BOLD responses), the optimal frequency (i.e., the frequency that elicit the strongest BOLD response), and the spatial distribution of generated BOLD responses are specific for each anesthetic used. Concurrent with anesthetic-dependent characteristics of the BOLD response, we found the pattern of stimulus-induced neuronal activity in the dentate gyrus is also specific for each anesthetic. Consequently, the anesthetic-specific influence on local signaling processes is the underlying cause for the observation that an identical stimulus elicits different BOLD responses under various anesthetics.

scholarly journals The cholinergic system modulates negative BOLD responses in the prefrontal cortex once electrical perforant pathway stimulation triggers neuronal afterdischarges in the hippocampus

2021 ◽  
pp. 0271678X2110498
Author(s):  
Alberto Arboit ◽  
Karla Krautwald ◽  
Frank Angenstein
Keyword(s):  
Prefrontal Cortex ◽  
Neuronal Activity ◽  
Cerebral Blood Volume ◽  
Bold Response ◽  
Perforant Pathway ◽  
Bold Responses ◽  
Stimulation Period ◽  
Negative Bold ◽  
The Right ◽  
Frequency Pulse

Repeated high-frequency pulse-burst stimulations of the rat perforant pathway elicited positive BOLD responses in the right hippocampus, septum and prefrontal cortex. However, when the first stimulation period also triggered neuronal afterdischarges in the hippocampus, then a delayed negative BOLD response in the prefrontal cortex was generated. While neuronal activity and cerebral blood volume (CBV) increased in the hippocampus during the period of hippocampal neuronal afterdischarges (h-nAD), CBV decreased in the prefrontal cortex, although neuronal activity did not decrease. Only after termination of h-nAD did CBV in the prefrontal cortex increase again. Thus, h-nAD triggered neuronal activity in the prefrontal cortex that counteracted the usual neuronal activity-related functional hyperemia. This process was significantly enhanced by pilocarpine, a mACh receptor agonist, and completely blocked when pilocarpine was co-administered with scopolamine, a mACh receptor antagonist. Scopolamine did not prevent the formation of the negative BOLD response, thus mACh receptors modulate the strength of the negative BOLD response.

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.

Evoked potentials and long-term potentiation in the mouse dentate gyrus after stimulation of the entorhinal cortex

1982 ◽  
Vol 75 (1) ◽  
pp. 134-148 ◽  
Author(s):  
Kathy Payne ◽  
Charles J. Wilson ◽  
Stephen Young ◽  
Eva Fifkova ◽  
Philip M. Groves
Keyword(s):  
Evoked Potentials ◽  
Dentate Gyrus ◽  
Entorhinal Cortex ◽  
Long Term Potentiation ◽  
Term Potentiation ◽  
Stimulation Of

scholarly journals Intracerebroventricular injection of oxidant and antioxidant molecules affects long-term potentiation in urethane anaesthetized rats

2008 ◽  
pp. 269-273
Author(s):  
A Viggiano ◽  
E Viggiano ◽  
M Monda ◽  
A Viggiano ◽  
S Ascione ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Dentate Gyrus ◽  
Long Term Potentiation ◽  
Control Group ◽  
High Frequency Stimulation ◽  
Perforant Pathway ◽  
Term Potentiation ◽  
Stimulation Of

Production of superoxide anions in the incubation medium of hippocampal slices can induce long-term potentiation (LTP). Other reactive oxygen species (ROS) such as hydrogen peroxide are able to modulate LTP and are likely to be involved in aging mechanisms. The present study explored whether intracerebroventricular (ICV) injection of oxidant or antioxidant molecules could affect LTP in vivo. With this aim in mind, field excitatory post-synaptic potentials (fEPSPs) elicited by stimulation of the perforant pathway were recorded in the dentate gyrus of the hippocampal formation in urethane-anesthetized rats. N-acetyl-Lcysteine, hydrogen peroxide (H2O2) or hypoxanthine/xanthineoxidase solution (a superoxide producing system) were administrated by ICV injection. The control was represented by a group injected with saline ICV. Ten minutes after the injection, LTP was induced in the granule cells of the dentate gyrus by high frequency stimulation of the perforant pathway. Neither the H2O2 injection or the N-acetyl-L-cysteine injection caused any variation in the fEPSP at the 10-min post-injection time point, whereas the superoxide generating system caused a significant increase in the fEPSP. Moreover, at 60 min after tetanic stimulation, all treatments attenuated LTP compared with the control group. These results show that ICV administration of oxidant or antioxidant molecules can modulate LTP in vivo in the dentate gyrus. Particularly, a superoxide producing system can induce potentiation of the synaptic response. Interestingly, ICV injection of oxidants or antioxidants prevented a full expression of LTP compared to the saline injection.

scholarly journals Early fMRI responses to somatosensory and optogenetic stimulation reflect neural information flow

2021 ◽  
Vol 118 (11) ◽  
pp. e2023265118
Author(s):  
Won Beom Jung ◽  
Geun Ho Im ◽  
Haiyan Jiang ◽  
Seong-Gi Kim
Keyword(s):  
Information Flow ◽  
Bold Response ◽  
Cortical Layers ◽  
Spatiotemporal Resolution ◽  
Somatosensory Stimulation ◽  
Network Analyses ◽  
Brain Functions ◽  
Optogenetic Stimulation ◽  
Bold Responses ◽  
Stimulation Of

Blood oxygenation level–dependent (BOLD) functional magnetic resonance imaging (fMRI) has been widely used to localize brain functions. To further advance understanding of brain functions, it is critical to understand the direction of information flow, such as thalamocortical versus corticothalamic projections. For this work, we performed ultrahigh spatiotemporal resolution fMRI at 15.2 T of the mouse somatosensory network during forepaw somatosensory stimulation and optogenetic stimulation of the primary motor cortex (M1). Somatosensory stimulation induced the earliest BOLD response in the ventral posterolateral nucleus (VPL), followed by the primary somatosensory cortex (S1) and then M1 and posterior thalamic nucleus. Optogenetic stimulation of excitatory neurons in M1 induced the earliest BOLD response in M1, followed by S1 and then VPL. Within S1, the middle cortical layers responded to somatosensory stimulation earlier than the upper or lower layers, whereas the upper cortical layers responded earlier than the other two layers to optogenetic stimulation in M1. The order of early BOLD responses was consistent with the canonical understanding of somatosensory network connections and cannot be explained by regional variabilities in the hemodynamic response functions measured using hypercapnic stimulation. Our data demonstrate that early BOLD responses reflect the information flow in the mouse somatosensory network, suggesting that high-field fMRI can be used for systems-level network analyses.

scholarly journals Postsynaptic and Spiking Activity of Pyramidal Cells, the Principal Neurons in the Rat Hippocampal CA1 Region, Does Not Control the Resultant BOLD Response: A Combined Electrophysiologic and fMRI Approach

2015 ◽  
Vol 35 (4) ◽  
pp. 565-575 ◽  
Author(s):  
Thomas Scherf ◽  
Frank Angenstein
Keyword(s):  
Pyramidal Cells ◽  
Bold Response ◽  
Ca1 Pyramidal Cells ◽  
Ca1 Region ◽  
Hippocampal Ca1 Region ◽  
Postsynaptic Activity ◽  
Hippocampal Ca1 ◽  
Bold Responses ◽  
Stimulation Of ◽  
Spiking Activity

The specific role of postsynaptic activity for the generation of a functional magnetic resonance imaging (fMRI) response was determined by a simultaneous measurement of generated field excitatory postsynaptic potentials (fEPSPs) and blood oxygen level-dependent (BOLD) response in the rat hippocampal CA1 region during electrical stimulation of the contralateral CA3 region. The stimulation electrode was placed either in the left CA3a/b or CA3c, causing the preferentially basal or apical dendrites of the pyramidal cells in the right CA1 to be activated. Consecutive stimulations with low-intensity stimulation trains (i.e., 16 pulses for 8 seconds) resulted in clear postsynaptic responses of CA1 pyramidal cells, but in no significant BOLD responses. In contrast, consecutive high-intensity stimulation trains resulted in stronger postsynaptic responses that came along with minor (during stimulation of the left CA3a/b) or substantial (during stimulation of the left CA3c) spiking activity of the CA1 pyramidal cells, and resulted in the generation of significant BOLD responses in the left and right hippocampus. Correlating the electrophysiologic parameters of CA1 pyramidal cell activity (fEPSP and spiking activity) with the resultant BOLD response revealed no positive correlation. Consequently, postsynaptic activity of pyramidal cells, the most abundant neurons in the CA1, is not directly linked to the measured BOLD response.

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