Lateralization of membrane-associated protein kinase C in rat piriform cortex: specific to operant training cues in the olfactory modality.

Rats were trained on an olfactory and a control modality (auditory or visual) discrimination task and brain membrane-associated protein kinase C (mPKC) was subsequently assessed using quantitative autoradiography of radiolabelled phorbol ester binding. In rats which received olfactory-cued training, mPKC showed a highly significant lateralization in the piriform cortex but not in the hippocampus. Both olfactory-trained rats and control modality rats showed a significant increase in mPKC in the hippocampus when compared to naive rats. Thus, while behavioral training procedures appeared to result in a hippocampal increase in the activated state of this enzyme as has been reported elsewhere, only olfactory learning produced an piriform cortex lateralization in the activated state of the enzyme. While the functional significance of such a change in the distribution of protein kinase C is still unclear, it does suggest that the monitoring of this enzyme's activational state may prove to be a useful tool in the study of memory formation in a wide variety of behavioral contexts.