The Journal of Neuroscience, December 15, 2000, 20(24):9034-9039
Bistable Behavior of Inhibitory Neurons Controlling Impulse
Traffic through the Amygdala: Role of a Slowly Deinactivating
K+ Current
Sébastien
Royer,
Marzia
Martina, and
Denis
Paré
Laboratoire de Neurophysiologie, Département de Physiologie,
Faculté de Médecine, Université Laval, Québec,
Canada G1K 7P4
The intercalated cell masses of the amygdala are clusters of
GABAergic neurons located strategically to influence behavioral responsiveness. Indeed, they receive glutamatergic sensory inputs from
the basolateral amygdaloid complex and generate feedforward inhibition
in neurons of the central amygdala that mediate important components of
fear responses. In the present study, using whole-cell recording
methods in coronal slices of the guinea pig amygdala, we show that the
activity of intercalated neurons is a function of their recent firing
history because they express an unusual voltage-dependent
K+ conductance (termed
ISD for slowly
deinactivating). This conductance activates in the subthreshold
regime, inactivates in response to suprathreshold depolarizations, and
deinactivates very slowly upon return to rest. As a result, after bouts
of suprathreshold activity, these cells enter a self-sustaining state
of heightened excitability associated with an increased input
resistance and a membrane depolarization. In turn, these changes
increase the likelihood that ongoing synaptic activity will trigger
orthodromic action potentials. However, because each orthodromic spike
"renews" the inactivation of ISD,
intercalated cells can remain hyperexcitable for a long time and, via
the central amygdaloid nucleus, exert a lasting influence on behavior.
Key words:
amygdala; intercalated cell masses; inhibition; potassium current; afterdepolarization; whole-cell recording; guinea
pig
Copyright © 2000 Society for Neuroscience 0270-6474/00/20249034-06$05.00/0
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