Changes in cortical and hippocampal ectonucleotidase activities in mice lacking cellular prion protein.

Animals lacking cellular prion protein (PrP(c)) expression are more susceptible to seizures. Adenosine is an endogenous anticonvulsant agent and it levels in the synaptic cleft are regulated by ectonucleotidases. We evaluated ectonucleotidase activities in synaptosomes from hippocampus and cerebral cortex of adult PrP(c) null mice and wild-type mice (genetic background 129/Sv X C57BL/6J). There was an increase (47%) in adenosine triphosphate (ATP) hydrolysis in hippocampal synaptosomes of PrP(c) knockout mice as compared with the wild-type animals. In cortical synaptosomes, ATP hydrolysis was similar in both PrP(c) mice and controls. However, there was a significant decrease in adenosine diphosphate (ADP) hydrolysis in both hippocampal (-39%) and cortical (-25%) synaptosomes in PrP(c) null animals compared to wild-type mice. Changes in brain ectonucleotidases activities related to modifications in the PrP(c) expression may contribute, at least in part, to the higher sensitivity to seizures of PrP(c) null mice.