Fear conditioning induces a lasting potentiation of synaptic currents in vitro.
The amygdala plays a critical role in the mediation of emotional responses, particularly fear, in both humans and animals. Fear conditioning, a conditioned learning paradigm, has served as a model for emotional learning in animals, and the neuroanatomical circuitry underlying the auditory fear-conditioning paradigm is well characterized. Synaptic transmission in the medial geniculate nucleus (MGN) to lateral nucleus of the amygdala (LA) pathway, a key segment of the auditory fear conditioning circuit, is mediated largely through N-methyl-D-aspartate (NMDA) and non-NMDA (such as alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)) glutamate receptors; the potential for neural plasticity in this pathway is suggested by its capacity to support long-term potentiation (LTP). Here we report a long-lasting increase in the synaptic efficacy of the MGN-LA pathway attributable to fear-conditioning itself, rather than an electrically induced model of learning. Fear-conditioned animals show a presynaptic facilitation of AMPA-receptor-mediated transmission, directly measured in vitro with whole-cell recordings in lateral amygdala neurons. These findings represent one of the first in vitro measures of synaptic plasticity resulting from emotional learning by whole animals.
McKernan
M G
MG
Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston 77555-1031, USA.
Shinnick-Gallagher
P
P
D000679:Amygdala / Q000502:physiology; D000818:Animals; D003214:Conditioning, Classical; D019706:Excitatory Postsynaptic Potentials; D005239:Fear / Q000502:physiology*; D005829:Geniculate Bodies / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D009474:Neurons / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism; D013569:Synapses / Q000502:physiology*
D018091:Receptors, AMPA