NMDA-Receptor-dependent synaptic activation of voltage-dependent calcium channels in basolateral amygdala.
Afferent stimulation of pyramidal cells in the basolateral amygdala produced mixed excitatory postsynaptic potentials (EPSPs) mediated by N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors during whole cell current-clamp recordings. In the presence of GABA(A) receptor blockade, the mixed EPSPs recruited a large "all-or-none" depolarizing event. This recruited event was voltage dependent and had a distinct activation threshold. An analogous phenomenon elicited by exogenous glutamate in the presence of tetrodotoxin (TTX) was blocked by Cd(2+), suggesting that the event was a Ca(2+) spike. Selective glutamatergic blockade revealed that these Ca(2+) spikes were recruited readily by single afferent stimulus pulses that elicited NMDA EPSPs. In contrast, non-NMDA EPSPs induced by single stimuli failed to elicit the Ca(2+) spike even at maximal stimulus intensities although these non-NMDA EPSPs depolarized the soma more effectively than mixed EPSPs. Elongation of non-NMDA EPSPs by cyclothiazide or brief trains of stimulation were also unable to elicit the Ca(2+) spike. Blockade of K(+) channels with intracellular Cs(+) enabled single non-NMDA EPSPs to activate the Ca(2+) spike. The finding that voltage-dependent calcium channels are activated preferentially by NMDA-receptor-mediated EPSPs provides a mechanism for NMDA-receptor-dependent plasticity independent of Ca(2+) influx through the NMDA receptor.
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- alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
- Tetrodotoxin
- Synapses
- Receptors, N-Methyl-D-Aspartate
- Rats, Sprague-Dawley
- Rats
- Quinoxalines
- Potassium Channel Blockers
- Patch-Clamp Techniques
- Neurology & Neurosurgery
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
- Tetrodotoxin
- Synapses
- Receptors, N-Methyl-D-Aspartate
- Rats, Sprague-Dawley
- Rats
- Quinoxalines
- Potassium Channel Blockers
- Patch-Clamp Techniques
- Neurology & Neurosurgery