We hypothesize that basal KOR activity in CeA is generated by an endogenous dynorphin tone that diminishes local GABA release and dampens inhibition, perhaps increasing activity of CeA output neurons. The CeA is the principal amygdaloid output nucleus that has a major influence on the activity of downstream effector regions responsible for producing physiological and behavioral responses to environmental stimuli (Cassell et al., 1999; Sah et al., 2003). Because CeA projections are mostly GABAergic, tonic KOR depression of inhibitory transmission in CeA likely results in inhibition of downstream targets. Reciprocally, KOR antagonist-induced increase of inhibitory transmission in CeA likely disinhibits downstream target structures.
