DISCUSSION
The present results uniquely extend recent observations in
rodents that stress-induced interactions between AEA and
CRH signaling modulate amygdala function associated with
anxiety and fear extinction (9). In rodents, stress-induced CRH
signaling via CRHR1 in the basolateral amygdala results in
increased activity of FAAH. The increased activity of this
catabolic enzyme subsequently results in decreased AEA
and a loss of inhibitory tone necessary for reducing anxiety
and maintaining fear extinction. Here, we demonstrate parallel
effects in humans using two functional genetic polymorphisms
to model variability in AEA inhibitory tone and CRH signaling.
Specifically, we found the least temporal habituation of the
basolateral amygdala, a neuroimaging correlate of fear extinc-
tion, in individuals who have relatively high AEA inhibitory tone
(i.e., FAAH 385A allele carriers) and relatively high CRH
signaling (i.e., CRHR1 A allele homozygotes). Moreover, the