Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
Address for correspondence: Dr. Pankaj Sah, The Division of Neuroscience, The John Curtin School of Medical Research, GPO Box 334, Canberra, ACT 2601, Australia. Voice: +61 2 6125 9692; fax: +61 2 6125 2687.
pankaj.sah{at}anu.edu.au
Ann. N.Y. Acad. Sci. 985: 67-77 (2003).
The amygdala plays a major role in the acquisition and expression
of fear conditioning. NMDA receptor-dependent synaptic plasticity
within the basolateral amygdala has been proposed to underlie
the acquisition and possible storage of fear memories. Here
the properties of fast glutamatergic transmission in the lateral
and central nuclei of the amygdala are presented. In the lateral
amygdala, two types of neurons, interneurons and projection
neurons, could be distinguished by their different firing properties.
Glutamatergic inputs to interneurons activated AMPA receptors
with inwardly rectifying current-voltage relations (I-Vs), whereas
inputs to projection neurons activated receptors that had linear
I-Vs, indicating that receptors on interneurons lack GluR2 subunits.
Inputs to projection neurons formed dual component synapses
with both AMPA and NMDA components, whereas at inputs to interneurons,
the contribution of NMDA receptors was very small. Neurons in
the central amygdala received dual component glutamatergic inputs
that activated AMPA receptors with linear I-Vs. NMDA receptor-mediated
EPSCs had slow decay time constants in the central nucleus.
Application of NR2B selective blockers ifenprodil or CP-101,606
blocked NMDA EPSCs by 70% in the central nucleus, but only by
30% in the lateral nucleus. These data show that the distribution
of glutamatergic receptors on amygdalar neurons is not uniform.
In the lateral amygdala, interneurons and pyramidal neurons
express AMPA receptors with different subunit compositions.
Synapses in the central nucleus activate NMDA receptors that
contain NR1 and NR2B subunits, whereas synapses in the lateral
nucleus contain receptors with both NR2A and NR2B subunits.
