Endogenous
adenosine in the brain is thought to prevent the development and spread of
seizures via a tonic
anticonvulsant effect. Brain levels of
adenosine are primarily regulated by the activity of
adenosine kinase. To establish a link between
adenosine kinase expression and seizure activity, we analyzed the expression of
adenosine kinase in the brain of control mice and in a
kainic acid-induced mouse model of mesial
temporal lobe epilepsy. Immunohistochemical analysis of brain sections of control mice revealed intense staining for
adenosine kinase, mainly in astrocytes, which were more or less evenly distributed throughout the brain, as well as in some neurons, particularly in olfactory bulb, striatum, and brainstem. In contrast, hippocampi lesioned by a unilateral
kainic acid injection displayed profound
astrogliosis and therefore a significant increase in
adenosine kinase immunoreactivity accompanied by a corresponding increase of
enzyme activity, which paralleled chronic recurrent seizure activity in this brain region. Accordingly,
seizures and interictal spikes were suppressed by the injection of a low dose of the
adenosine kinase inhibitor
5-iodotubercidin. We conclude that overexpression of
adenosine kinase in discrete parts of the epileptic hippocampus may contribute to the development and progression of seizure activity.