Learning-related changes in the levels of protein kinase C βII in rat lateral/basolateral amygdala in vivo and in vitro: effects of conditioning and laterality

Abstract

The lateral and basolateral nuclei (LA/BLA) are critically important for classical fear conditioning and the storage of fear memories. These amygdalar nuclei exhibit long-term potentiation (LTP) protein kinase C (PKC) is one of several kinases that may be important for learning in the amygdala. We examined the changes in the PKC βII, induced in the LA/BLA by classical fear conditioning in intact animals and LTP in brain slices. PKC βII levels were compared among groups that received: (a) no tones or shocks; (b) paired tones/shocks; and (c) unpaired tones/shocks. PKC βII levels from the LA/BLA of the right hemisphere were larger in the unpaired group when compared with the paired group. A difference measure ((R−L)/(R+L)) showed the relative levels of PKC βII for the unpaired group to have a right>left relation that was different from both box alone and paired groups (both left>right). PKC βII levels in LA/BLA from slices that showed LTP were increased relative to control slices from the left hemisphere, but uniformly high levels were found in control and LTP slices from the right hemisphere. We conclude that levels of PKC βII in the rat LA/BLA can be increased and possibly activated by learning-related afferent inputs, but the magnitudes of level increases depend upon baseline levels of PKC βII. The relative levels of PKC βII in right and left hemispheres may be a better indicator of learning-related changes in animals experiencing classical fear conditioning.