Long-term depression in lateral amygdala
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1
University Medical Center Mainz, Institute of Physiological Chemistry and Pathobiochemistry, Germany
The convergence of conditioned and unconditioned stimuli (CS and US) into the lateral amygdala (LA) serves as a substrate for an adequate fear response in vivo. This well-known Pavlovian paradigm modulates the synaptic plasticity of neurons that can be proved by long-term potentiation (LTP) phenomenon in vitro. Although, there is an increasing body of evidence for existence of LTP in amygdala, only a few studies were able to show a long-term depression (LTD) of excitation in this structure. We used coronal brain slices which were prepared from one month-old mice in order to unravel LTD in glutamatergic pyramidal cells of the LA. These neurones were distinguished by regular firings and frequency adaptation properties of their action potentials, evoked from the resting membrane potential. The whole-cell excitatory postsynaptic currents (EPSCs) were evoked in the presence of picrotoxin by the stimulation of cortical inputs into the LA at 0.33 Hz. After obtaining a stable baseline response at holding potential of –70 mV, a stimulation paradigm at 1 Hz was employed at the same membrane potential. The different durations of stimulation (ranging between 1.5 - 24 min) were tested first in the same neuron in order to define an optimal effective diapason, but the intensity was kept constant. The latter paradigm resulted in a stepwise LTD with gradually increasing magnitude under these conditions. The two initial durations (1.5 and 3 min) did not trigger any LTD and rather non-significant tendencies toward potentiation were observed: 113.9 ± 15.4 and 105.0 ± 14.4% of baseline (n = 5, P = 0.9), respectively. A further increase in duration of paradigm significantly suppressed the amplitude of EPSCs recorded in pyramidal cells: 75.3 ± 3.8, 64.5 ± 8.8 and 42.3 ± 11.5% of baseline (n = 3-4, P < 0.05) at 6, 12 and 24 min durations, respectively. Therefore, further experiments were performed directly using effective durations of stimulation, which revealed a comparable LTD. In conclusion, this plasticity might be an opposite mechanism to LTP that underlies a formation of fear associated memories in the amygdala.
Keywords:
Amygdala
Conference:
41st European Brain and Behaviour Society Meeting, Rhodes Island, Greece, 13 Sep - 18 Sep, 2009.
Presentation Type:
Poster Presentation
Topic:
Poster presentations
Citation:
Psyrakis
D,
Wehrmeister
M,
Bonni
K,
Lutz
B and
Kodirov
S
(2009). Long-term depression in lateral amygdala.
Conference Abstract:
41st European Brain and Behaviour Society Meeting.
doi: 10.3389/conf.neuro.08.2009.09.265
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Received:
12 Jun 2009;
Published Online:
12 Jun 2009.
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Correspondence:
Dimitrios Psyrakis, University Medical Center Mainz, Institute of Physiological Chemistry and Pathobiochemistry, Mainz, Germany, Sodikdjon.Kodirov@utb.edu