Hippocampal protein kinase C activity is reduced in poor spatial learners

Activation of protein kinase C (PKC) via neurotransmitter coupling processes has been associated with long-term potentiation (LTP) or classical conditioning, but whether natural variation in PKC activity affects learning performance remains to be determined. Inbred strains of mice differ in their ability to exhibit spatial reference memory as measured by the Morris water task. C57BL/6Ibg (C57) mice perform the task better than DBA/2Ibg (DBA) mice, which show relatively little spatial preference. Hippocampal PKC activity extracted from the particulate fraction was lower in DBA mice than in C57 mice. To examine the potential relationship of PKC activity with spatial learning performance, 11 C57BL/6J x DBA/2J recombinant inbred strains (BXD RIs) were trained in the place learning version of the Morris water task. Cortical and hippocampal PKC activities were measured. Variation in spatial learning performance and PKC activity from cortex and hippocampus was observed. A positive significant correlation was observed between measures of spatial learning accuracy and hippocampal PKC in these strains. No correlation was observed between spatial learning accuracy and cortical PKC activity. These data suggest that animals with lower hippocampal PKC activity may have problems performing spatial reference memory tasks with the same degree of accuracy as those with higher hippocampal PKC activity.