scholarly journals GABAergic Transmission in the Basolateral Amygdala Differentially Modulates Plasticity in the Dentate Gyrus and the CA1 Areas

2020 ◽  
Vol 21 (11) ◽  
pp. 3786 ◽  
Author(s):  
Rose-Marie Vouimba ◽  
Rachel Anunu ◽  
Gal Richter-Levin
Keyword(s):  
Dentate Gyrus ◽  
Basolateral Amygdala ◽  
Long Term Potentiation ◽  
Brain Regions ◽  
Stressful Events ◽  
Perforant Path ◽  
Tetanic Stimulation ◽  
Gabaergic Neurotransmission ◽  
Hippocampal Commissure ◽  
Stimulation Of

The term “metaplasticity” is used to describe changes in synaptic plasticity sensitivity following an electrical, biochemical, or behavioral priming stimulus. For example, priming the basolateral amygdala (BLA) enhances long-term potentiation (LTP) in the dentate gyrus (DG) but decreases LTP in the CA1. However, the mechanisms underlying these metaplastic effects are only partly understood. Here, we examined whether the mechanism underlying these effects of BLA priming involves intra-BLA GABAergic neurotransmission. Low doses of muscimol, a GABAA receptor (GABAAR) agonist, were microinfused into the rat BLA before or after BLA priming. Our findings show that BLA GABAAR activation via muscimol mimicked the previously reported effects of electrical BLA priming on LTP in the perforant path and the ventral hippocampal commissure-CA1 pathways, decreasing CA1 LTP and increasing DG LTP. Furthermore, muscimol application before or after tetanic stimulation of the ventral hippocampal commissure-CA1 pathways attenuated the BLA priming-induced decrease in CA1 LTP. In contrast, muscimol application after tetanic stimulation of the perforant path attenuated the BLA priming-induced increase in DG LTP. The data indicate that GABAAR activation mediates metaplastic effects of the BLA on plasticity in the CA1 and the DG, but that the same GABAAR activation induces an intra-BLA form of metaplasticity, which alters the way BLA priming may modulate plasticity in other brain regions. These results emphasize the need for developing a dynamic model of BLA modulation of plasticity, a model that may better capture processes underlying memory alterations associated with emotional arousing or stressful events.

Heterosynaptic LTD and Depotentiation in the Medial Perforant Path of the Dentate Gyrus in the Freely Moving Rat

1997 ◽  
Vol 77 (2) ◽  
pp. 571-578 ◽  
Author(s):  
Valérie Doyère ◽  
Bolek Srebro ◽  
Serge Laroche
Keyword(s):  
Dentate Gyrus ◽  
High Frequency ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
High Frequency Stimulation ◽  
Tetanic Stimulation ◽  
Frequency Stimulation ◽  
Freely Moving ◽  
Stimulation Of

Doyère, Valérie, Bolek Srebro, and Serge Laroche. Heterosynaptic LTD and depotentiation in the medial perforant path of the dentate gyrus in the freely moving rat. J. Neurophysiol. 77: 571–578, 1997. We examined the characteristics of heterosynaptic long-term depression (LTD) and depotentiation of previously established long-term potentiation (LTP) in the medial and lateral entorhinal afferents to the dentate gyrus in the awake rat. Rats were prepared for chronic recording of dentate gyrus evoked potentials to activation of the medial and lateral perforant paths. This study in awake rats confirms that heterosynaptic LTD can be induced at inactive medial perforant path synapses in conjunction with the induction of LTP produced by high-frequency stimulation of the lateral perforant path. This form of LTD was long lasting and reversible by tetanic stimulation delivered to the depressed pathway. In contrast, tetanic stimulation of the medial perforant path had only a small heterosynaptic effect on the lateral pathway, suggesting that the two input pathways to the dentate gyrus are not symmetrical in their ability to induce heterosynaptic LTD. We also examined the ability of high-frequency stimulation of one pathway to produce depotentiation of the other pathway. We found that when LTP was first induced in the medial perforant path, depotentiation was induced heterosynaptically by tetanization of the lateral pathway. Both newly established LTP (30 min) and LTP induced and saturated by repeated tetanic stimulation over several days can be depotentiated heterosynaptically. Moreover, depotentiation of the medial perforant path synapses was found to be linearly correlated with the magnitude of LTP induced in the lateral perforant path synapses, and subsequent tetanic stimulation of the depotentiated medial perforant path restored LTP to an extent that counterbalanced depotentiation. The saturation and repotentiation experiments provide clear support for the conclusion that the rapid reversal of LTP reflects true depotentiation of the medial input. Again, as with heterosynaptic LTD, tetanization of the medial perforant path had little effect on previously induced LTP in the lateral path. These results provide evidence that medial perforant path synapses can be depressed and depotentiated heterosynaptically. They suggest that in the intact rat synaptic changes in the afferents to the dentate gyrus from the lateral entorhinal cortex exert powerful control over ongoing or recent synaptic plasticity in the medial entorhinal afferents.

Low-frequency stimulation of the perforant path produces long-term potentiation in the dentate gyrus of unanesthetized rats

1983 ◽  
Vol 61 (10) ◽  
pp. 1156-1161 ◽  
Author(s):  
R. W. Skelton ◽  
J. J. Miller ◽  
A. G. Phillips
Keyword(s):  
Dentate Gyrus ◽  
Low Frequency ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
High Frequency Stimulation ◽  
Synaptic Efficacy ◽  
Term Potentiation ◽  
Frequency Stimulation ◽  
Stimulation Of

Brief periods of high-frequency stimulation of hippocampal afferents produce long-term potentiation (LTP) of synaptic transmission, but the minimum frequency capable of inducing this alteration in synaptic efficacy has not been specified. The present study used the repeated measurement of input–output curves in the perforant path – dentate gyrus system of freely moving rats to monitor synaptic efficacy and found that stimulation at 0.2 Hz, but not 0.04 Hz produced LTP. These results suggest that the minimum stimulation frequency capable of producing LTP is lower than previously described. Possible reasons for the discrepancy between the present and previous findings are discussed, along with the implications of low-frequency potentiation.

Medial amygdala enhances synaptic transmission and synaptic plasticity in the dentate gyrus of rats in vivo

1995 ◽  
Vol 74 (5) ◽  
pp. 2201-2203 ◽  
Author(s):  
Y. Ikegaya ◽  
K. Abe ◽  
H. Saito ◽  
N. Nishiyama
Keyword(s):  
Synaptic Plasticity ◽  
Synaptic Transmission ◽  
Dentate Gyrus ◽  
High Frequency ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
High Frequency Stimulation ◽  
Medial Amygdala ◽  
Frequency Stimulation ◽  
Stimulation Of

1. The present experiment was designed to test whether synaptic transmission and synaptic plasticity in the dentate gyrus were modulated by the medial amygdala (MeA). Field potentials in the dentate gyrus (DG) evoked by stimulations of the medial perforant path (PP) were extracellularly recorded in anesthetized rats. 2. Although single-pulse stimulation of the MeA augmented PP stimulation-evoked population spike amplitude in the DG transiently, high-frequency stimulation (100 Hz for 1 s) of the MeA induced long-lasting enhancement of synaptic transmission that was not occluded by PP tetanus-induced long-term potentiation (LTP). 3. When high-frequency stimulation of the MeA was applied concurrently with weak tetanus of the PP, which alone induced only marginal LTP, the magnitude of LTP increased considerably. 4. These results demonstrate that neuron activities in the MeA induce short- and long-lasting changes in the excitability of the PP-DG synapses and thereby enhance their synaptic plasticity.

scholarly journals Stimulation of Perforant Path Fibers Induces LTP Concurrently in Amygdala and Hippocampus in Awake Freely Behaving Rats

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
J. Harry Blaise ◽  
Rachel A. Hartman
Keyword(s):  
Learning And Memory ◽  
Basolateral Amygdala ◽  
Peak Level ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Term Potentiation ◽  
Freely Behaving ◽  
Stimulation Of

Long-term potentiation (LTP) which has long been considered a cellular model for learning and memory is defined as a lasting enhancement in synaptic transmission efficacy. This cellular mechanism has been demonstrated reliably in the hippocampus and the amygdala—two limbic structures implicated in learning and memory. Earlier studies reported on the ability of cortical stimulation of the entorhinal cortex to induce LTP simultaneously in the two sites. However, to retain a stable baseline of comparison with the majority of the LTP literature, it is important to investigate the ability of fiber stimulation such as perforant path activation to induce LTP concurrently in both structures. Therefore, in this paper we report on concurrent LTP in the basolateral amygdala (BLA) and the dentate gyrus (DG) subfield of the hippocampus induced by theta burst stimulation of perforant path fibers in freely behaving Sprague-Dawley rats. Our results indicate that while perforant path-evoked potentials in both sites exhibit similar triphasic waveforms, the latency and amplitude of BLA responses were significantly shorter and smaller than those of DG. In addition, we observed no significant differences in either the peak level or the duration of LTP between DG and BLA.

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