NMDA Receptor-Dependent Synaptic Activation of Voltage-Dependent Calcium Channels in Basolateral Amygdala. Jeffrey L. Calton3, Maeng-Hee Kang4, Wilkie A. Wilson2,4, and Scott D. Moore1,3. Divisions of Psychiatry1 and Neurology Research2, Durham VA Medical Center, and Departments of Psychiatry3 and Pharmacology4, Duke University Medical Center, Durham, NC.
APStracts 6:0505N, 1999.
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 GABAA receptor blockade, the mixed EPSPs recruited a large Aall-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++, suggesting that the event was a Ca++ spike. Selective glutamatergic blockade revealed that these Ca++ spikes were readily recruited by single afferent stimulus pulses that elicited NMDA EPSPs. In contrast, non-NMDA EPSPs induced by single stimuli failed to elicit the Ca++ 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++ spike. Blockade of K+ channels with intracellular Cs+ enabled single non-NMDA EPSPs to activate the Ca++ spike. The finding that voltage-dependent calcium channels (VDCCs) are preferentially activated by NMDA receptor-mediated EPSPs provides a mechanism for NMDA receptor-dependent plasticity independent of Ca++ influx through the NMDA receptor.
Received 1 March 1999; accepted in final form 6 October 1999.
APS Manuscript Number J177-9.
Article publication pending Journal of Neurophysiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 21 December 1999