Duration of NMDA-Dependent Synaptic Potentiation in Piriform Cortex In Vivo Is Increased After Epileptiform Bursting

1998 ◽  
Vol 80 (4) ◽  
pp. 1623-1629 ◽  
Author(s):  
A. Kapur ◽  
L. B. Haberly
Keyword(s):  
Seizure Activity ◽  
Piriform Cortex ◽  
Long Term Potentiation ◽  
Excitatory Postsynaptic Potential ◽  
Synaptic Potentiation ◽  
Lateral Olfactory Tract ◽  
Afferent Fibers ◽  
Stimulation Of

Kapur, A. and L. B. Haberly. Duration of NMDA-dependent synaptic potentiation in piriform cortex in vivo is increased after epileptiform bursting. J. Neurophysiol. 80: 1623–1629, 1998. Stimulation of afferent fibers with current pulse trains has been reported to induce long-term potentiation (LTP) in piriform cortex in vitro but not in vivo. LTP has been observed in vivo only when trains are paired with behavioral reinforcement and as a consequence of kindled epileptogenesis. This study was undertaken in the urethan-anesthetized rat to determine if the reported failures to observe pulse-train evoked LTP in vivo may be related to a lesser persistence rather than lack of occurrence, if disinhibition might facilitate induction, and to examine the nature of the relationship between seizure activity and LTP. Stimulation of afferent fibers in the lateral olfactory tract with θ-burst trains under control conditions potentiated the monosynaptic field excitatory postsynaptic potential (EPSP) by approximately the same extent (20.3 ± 2%; n = 12) as reported for the slice. However, in contrast to the slice, potentiation in vivo decayed to a low level within 1–2 h after induction (70% loss in 1.5 h, on average). The N-methyl-d-aspartate (NMDA)-receptor antagonists d-APV and MK-801 blocked the induction of this decremental potentiation. Pharmacological reduction of γ-aminobutyric acid–mediated inhibition at the recording site did not increase the duration of potentiation. In contrast, θ-burst stimulation applied after recovery from a period of epileptiform bursting induced stable NMDA-dependent potentiation. Mean increase in the population EPSP was approximately the same as under control conditions (21 ± 2%; n = 6), but in five of six experiments there was little or no decay in potentiation for the duration of the monitoring period (≤6 h). It is concluded that seizure activity has an enabling action on the induction of persistent synaptic potentiation by stimulus trains that bypasses the need for behavioral reinforcement.

scholarly journals Epileptiform Discharges With In-Vivo-Like Features in Slices of Rat Piriform Cortex With Longitudinal Association Fibers

2001 ◽  
Vol 86 (5) ◽  
pp. 2445-2460 ◽  
Author(s):  
Rezan Demir ◽  
Lewis B. Haberly ◽  
Meyer B. Jackson
Keyword(s):  
Seizure Activity ◽  
Epileptiform Activity ◽  
Piriform Cortex ◽  
Brain Slices ◽  
Epileptiform Discharges ◽  
Local Circuitry ◽  
Association Fibers ◽  
Discharge Propagation

Brain slices serve as useful models for the investigation of epilepsy. However, the preparation of brain slices disrupts circuitry and severs axons, thus complicating efforts to relate epileptiform activity in vitro to seizure activity in vivo. This issue is relevant to studies in transverse slices of the piriform cortex (PC), the preparation of which disrupts extensive rostrocaudal fiber systems. In these slices, epileptiform discharges propagate slowly and in a wavelike manner, whereas such discharges in vivo propagate more rapidly and jump abruptly between layers. The objective of the present study was to identify fiber systems responsible for these differences. PC slices were prepared by cutting along three different nearly orthogonal planes (transverse, parasagittal, and longitudinal), and epileptiform discharges were imaged with a voltage-sensitive fluorescent dye. Interictal-like epileptiform activity was enabled by either a kindling-like induction process or disinhibition with bicuculline. The pattern of discharge onset was very similar in slices cut in different planes. As described previously in transverse PC slices, discharges were initiated in the endopiriform nucleus (En) and adjoining regions in a two-stage process, starting with low-amplitude “plateau activity” at one site and leading to an accelerating depolarization and discharge onset at another nearby site. The similar pattern of onset in slices of various orientations indicates that the local circuitry and neuronal properties in and around the En, rather than long-range fibers, assume dominant roles in the initiation of epileptiform activity. Subtle variations in the onset site indicate that interneurons can fine tune the site of discharge onset. In contrast to the mode of onset, discharge propagation showed striking variations. In longitudinal slices, where rostrocaudal association fibers are best preserved, discharge propagation resembled in vivo seizure activity in the following respects: propagation was as rapid as in vivo and about two to three times faster than in other slices; discharges jumped abruptly between the En and PC; and discharges had large amplitudes in superficial layers of the PC. Cuts in longitudinal slices that partially separated the PC from the En eliminated these unique features. These results help clarify why epileptiform activity differs between in vitro and in vivo experiments and suggest that rostrocaudal pyramidal cell association fibers play a major role in the propagation of discharges in the intact brain. The longitudinal PC slice, which best preserves these fibers, is ideally suited for the study their role.

scholarly journals Heterosynaptic modulation of evoked synaptic potentials in layer II of the entorhinal cortex by activation of the parasubiculum

2016 ◽  
Vol 116 (2) ◽  
pp. 658-670 ◽  
Author(s):  
Daniel W. Sparks ◽  
C. Andrew Chapman
Keyword(s):  
Entorhinal Cortex ◽  
Piriform Cortex ◽  
Theta Activity ◽  
Pulse Interval ◽  
Facilitation Effect ◽  
Layer I ◽  
Cortical Inputs ◽  
Stimulation Of

The superficial layers of the entorhinal cortex receive sensory and associational cortical inputs and provide the hippocampus with the majority of its cortical sensory input. The parasubiculum, which receives input from multiple hippocampal subfields, sends its single major output projection to layer II of the entorhinal cortex, suggesting that it may modulate processing of synaptic inputs to the entorhinal cortex. Indeed, stimulation of the parasubiculum can enhance entorhinal responses to synaptic input from the piriform cortex in vivo. Theta EEG activity contributes to spatial and mnemonic processes in this region, and the current study assessed how stimulation of the parasubiculum with either single pulses or short, five-pulse, theta-frequency trains may modulate synaptic responses in layer II entorhinal stellate neurons evoked by stimulation of layer I afferents in vitro. Parasubicular stimulation pulses or trains suppressed responses to layer I stimulation at intervals of 5 ms, and parasubicular stimulation trains facilitated layer I responses at a train-pulse interval of 25 ms. This suggests that firing of parasubicular neurons during theta activity may heterosynaptically enhance incoming sensory inputs to the entorhinal cortex. Bath application of the hyperpolarization-activated cation current (Ih) blocker ZD7288 enhanced the facilitation effect, suggesting that cholinergic inhibition of Ih may contribute. In addition, repetitive pairing of parasubicular trains and layer I stimulation induced a lasting depression of entorhinal responses to layer I stimulation. These findings provide evidence that theta activity in the parasubiculum may promote heterosynaptic modulation effects that may alter sensory processing in the entorhinal cortex.

Alterations in Piriform and Bulbar Activity/Excitability/Coupling Upon Amyloid-β Administration in vivo Related to Olfactory Dysfunction

2021 ◽  
pp. 1-17
Author(s):  
Ignacio Martínez-García ◽  
Rebeca Hernández-Soto ◽  
Benjamín Villasana-Salazar ◽  
Benito Ordaz ◽  
Fernando Peña-Ortega
Keyword(s):  
Piriform Cortex ◽  
Brain Slices ◽  
Amyloid Β ◽  
Olfactory Dysfunction ◽  
Network Activity ◽  
Pathological Changes ◽  
Olfactory Pathway ◽  
Lateral Olfactory Tract

Background: Deficits in odor detection and discrimination are premature symptoms of Alzheimer’s disease (AD) that correlate with pathological signs in the olfactory bulb (OB) and piriform cortex (PCx). Similar olfactory dysfunction has been characterized in AD transgenic mice that overproduce amyloid-β (Aβ), which can be prevented by reducing Aβ levels by immunological and pharmacological means, suggesting that olfactory dysfunction depends on Aβ accumulation and Aβ-driven alterations in the OB and/or PCx, as well as on their activation. However, this possibility was not directly tested before. Objective: To characterize the effects of Aβ on OB and PCx excitability/coupling and on olfaction. Methods: Aβ oligomerized solution (containing oligomers, monomers, and protofibrils) or its vehicle were intracerebroventricularlly injected two weeks before OB and PCx excitability and synchrony were evaluated through field recordings in vivo and in brain slices. Synaptic transmission from the OB to the PCx was also evaluated in vitro. Olfaction was assessed through the habituation/dishabituation test. Results: Aβ did not affect lateral olfactory tract transmission into the PCx but reduced odor habituation and cross-habituation. This olfactory dysfunction was related to a reduction of PCx and OB network activity power in vivo. Moreover, the coherence between PCx-OB activities was also reduced by Aβ. Finally, Aβ treatment exacerbated the 4-aminopyridine-induced excitation in the PCx in vitro. Conclusion: Our results show that Aβ-induced olfactory dysfunction involves a complex set of pathological changes at different levels of the olfactory pathway including alterations in PCx excitability and its coupling with the OB. These pathological changes might contribute to hyposmia in AD.

Implications of Kindling And Quenching For the Possible Frequency Dependence Of rTMS

CNS Spectrums ◽  
1997 ◽  
Vol 2 (1) ◽  
pp. 54-60 ◽  
Author(s):  
R. M. Post ◽  
T. Kimbrell ◽  
M. Frye ◽  
M. George ◽  
U. McCann ◽  
...  
Keyword(s):  
Low Frequency ◽  
Repeated Administration ◽  
Long Term Potentiation ◽  
Synaptic Function ◽  
Seizure Threshold ◽  
Frequency Stimulation ◽  
Stimulation Of

AbstractKindling involves repeated administration of brief high-frequency electrophysiological stimulation of the brain at initially subthreshold intensities that eventually evoke full-blown seizures. It has thus been used not only as a model of epileptogenesis, but of long-term neuronal memory. Quenching is a phenomenon that utilizes low-frequency stimulation for much longer periods of time (eg, 1 Hz for 15 minutes), and appears to exert preventive effects on the development of kindling and inhibit the manifestation of full-blown kindled seizures by markedly increasing the amygdala afterdischarge and seizure threshold. (See also “Kindling and Quenching: Conceptual Implications for rTMS,” by Weiss and Post, page 32). The parameters of kindling and quenching with intracerebral stimulation of the amygdala in vivo are highly similar to those achieved in vitro in hippocampai slice preparations for inducing long-term potentiation (LTP) and longterm depression (LTD), respectively. These neuroplastic changes are relatively long lasting and appear reversible at the level of synaptic function with either LTD or LTP capable of countering the effects of the other.

Thrombopoietin-Induced Stimulation of Megakaryocyte- Enriched Bone Marrow Cultures

1979 ◽  
Author(s):  
K. L. Kellar ◽  
B. L. Evatt ◽  
C. R. McGrath ◽  
R. B. Ramsey
Keyword(s):  
Bone Marrow ◽  
Dna Synthesis ◽  
Bone Marrow Cells ◽  
Rabbit Plasma ◽  
Bone Marrow Cultures ◽  
Plasma Fractions ◽  
Marrow Cultures ◽  
Stimulation Of

Liquid cultures of bone marrow cells enriched for megakaryocytes were assayed for incorporation of 3H-thymidine (3H-TdR) into acid-precipitable cell digests to determine the effect of thrombopoietin on DNA synthesis. As previously described, thrombopoietin was prepared by ammonium sulfate fractionation of pooled plasma obtained from thrombocytopenic rabbits. A control fraction was prepared from normal rabbit plasma. The thrombopoietic activity of these fractions was determined in vivo with normal rabbits as assay animals and the rate of incorporation of 75Se-selenomethionine into newly formed platelets as an index of thrombopoietic activity of the infused material. Guinea pig megakaryocytes were purified using bovine serum albumin gradients. Bone marrow cultures containing 1.5-3.0x104 cells and 31%-71% megakaryocytes were incubated 18 h in modified Dulbecco’s MEM containing 10% of the concentrated plasma fractions from either thrombocytopenic or normal rabbits. In other control cultures, 0.9% NaCl was substituted for the plasma fractions. 3H-TdR incorporation was measured after cells were incubated for 3 h with 1 μCi/ml. The protein fraction containing thrombopoietin-stimulating activity caused a 25%-31% increase in 3H-TdR incorporation over that in cultures which were incubated with the similar fraction from normal plasma and a 29% increase over the activity in control cultures to which 0.9% NaCl had been added. These data suggest that thrombopoietin stimulates DNA synthesis in megakaryocytes and that this tecnique may be useful in assaying thrombopoietin in vitro.

scholarly journals Contamination of erythropoietin by endotoxin: in vivo and in vitro effects on murine erythropoiesis

Blood ◽  
1979 ◽  
Vol 54 (1) ◽  
pp. 146-158 ◽  
Author(s):  
KS Zuckerman ◽  
PJ Quesenberry ◽  
J Levin ◽  
R Sullivan
Keyword(s):  
Significant Inhibition ◽  
Erythropoietic Activity ◽  
Limulus Amebocyte Lysate ◽  
Endogenous Erythropoietin ◽  
Significant Change ◽  
In Vitro Effects ◽  
Stimulation Of

Abstract Endotoxin was detected in all erythropoietin preparations tested and was removed from four lots, without loss of erythropoietic activity, by adsorption with limulus amebocyte lysate. Comparison of adsorbed (endotoxin-depleted) and nonadsorbed (endotoxin-containing) erythropoietin preparations demonstrated significant inhibition of CFU- e and BFU-e in vitro by nonadsorbed erythropoietin at concentrations higher than 0.25 U/ml and 2.0 U/ml, respectively. CFU-e and BFU-e were inhibited significantly by readdition in vitro of 10(-5)-10(-3) mug of endotoxin per unit of limulus-adsorbed erythropoietin. Administration of saline or 6 U of nonadsorbed or adsorbed erythropoietin twice a day for 4 days of CF1 mice resulted in reticulocyte counts of 2.1%, 9.9%, and 15.9%, respectively. Nonadsorbed erythropoietin resulted in a 29% decrease in erythropoiesis, a 42% decrease in CFU-e, and a 16% increase in granulopoiesis in the marrow, whereas adsorbed erythropoietin caused a 28% increase in erythropoiesis, no significant change in CFU-e and a 19% decrease in granulopoiesis in the marrow. Both preparations resulted in marked increases in splenic erythropoiesis and granulopoiesis. The effects of adsorbed erythropoietin are similar to those produced following stimulation of hematopoiesis by endogenous erythropoietin. Hemopoietic changes induced by nonadsorbed erythropoietin in vivo and in vitro are affected substantially by contamination of the erythropoietin preparations with endotoxin.

scholarly journals Protein kinase D promotes plasticity-induced F-actin stabilization in dendritic spines and regulates memory formation

2015 ◽  
Vol 210 (5) ◽  
pp. 771-783 ◽  
Author(s):  
Norbert Bencsik ◽  
Zsófia Szíber ◽  
Hanna Liliom ◽  
Krisztián Tárnok ◽  
Sándor Borbély ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Protein Kinase ◽  
Dendritic Spines ◽  
Morphological Changes ◽  
Long Term Potentiation ◽  
Memory Formation ◽  
Protein Kinase D

Actin turnover in dendritic spines influences spine development, morphology, and plasticity, with functional consequences on learning and memory formation. In nonneuronal cells, protein kinase D (PKD) has an important role in stabilizing F-actin via multiple molecular pathways. Using in vitro models of neuronal plasticity, such as glycine-induced chemical long-term potentiation (LTP), known to evoke synaptic plasticity, or long-term depolarization block by KCl, leading to homeostatic morphological changes, we show that actin stabilization needed for the enlargement of dendritic spines is dependent on PKD activity. Consequently, impaired PKD functions attenuate activity-dependent changes in hippocampal dendritic spines, including LTP formation, cause morphological alterations in vivo, and have deleterious consequences on spatial memory formation. We thus provide compelling evidence that PKD controls synaptic plasticity and learning by regulating actin stability in dendritic spines.

Metabolic importance of Na+/K+-ATPase activity during sea urchin development.

1997 ◽  
Vol 200 (22) ◽  
pp. 2881-2892 ◽  
Author(s):  
P Leong ◽  
D Manahan
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Sea Urchin ◽  
Sodium Pump ◽  
Sea Water ◽  
Strongylocentrotus Purpuratus ◽  
Lytechinus Pictus ◽  
Stimulation Of

Early stages of animal development have high mass-specific rates of metabolism. The biochemical processes that establish metabolic rate and how these processes change during development are not understood. In this study, changes in Na+/K+-ATPase activity (the sodium pump) and rate of oxygen consumption were measured during embryonic and early larval development for two species of sea urchin, Strongylocentrotus purpuratus and Lytechinus pictus. Total (in vitro) Na+/K+-ATPase activity increased during development and could potentially account for up to 77 % of larval oxygen consumption in Strongylocentrotus purpuratus (pluteus stage) and 80 % in Lytechinus pictus (prism stage). The critical issue was addressed of what percentage of total enzyme activity is physiologically active in living embryos and larvae and thus what percentage of metabolism is established by the activity of the sodium pump during development. Early developmental stages of sea urchins are ideal for understanding the in vivo metabolic importance of Na+/K+-ATPase because of their small size and high permeability to radioactive tracers (86Rb+) added to sea water. A comparison of total and in vivo Na+/K+-ATPase activities revealed that approximately half of the total activity was utilized in vivo. The remainder represented a functionally active reserve that was subject to regulation, as verified by stimulation of in vivo Na+/K+-ATPase activity in the presence of the ionophore monensin. In the presence of monensin, in vivo Na+/K+-ATPase activities in embryos of S. purpuratus increased to 94 % of the maximum enzyme activity measured in vitro. Stimulation of in vivo Na+/K+-ATPase activity was also observed in the presence of dissolved alanine, presumably due to the requirement to remove the additional intracellular Na+ that was cotransported with alanine from sea water. The metabolic cost of maintaining the ionic balance was found to be high, with this process alone accounting for 40 % of the metabolic rate of sea urchin larvae (based on the measured fraction of total Na+/K+-ATPase that is physiologically active in larvae of S. purpuratus). Ontogenetic changes in pump activity and environmentally induced regulation of reserve Na+/K+-ATPase activity are important factors that determine a major proportion of the metabolic costs of sea urchin development.

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