Changes in striatal cholinergic, gabaergic, dopaminergic and serotoninergic biochemical markers after kainic acid-induced thalamic lesions in the rat.

Kinetic parameters of 3H-choline, 3H-GABA and 3H-dopamine (DA) uptakes in striatal homogenates containing nerve endings were determined 2 to 3 weeks after kainic acid injection into the ipsilateral "centre médian"-parafascicular complex area of the thalamus in the rat. Results showed a marked decrease in 3H-choline uptake concomitant with a selective decrease in Vmax. Data also showed a large decrease in 3H-GABA uptake resulting from a decreased affinity of uptake sites for their substrate. These data were associated with the previously described decrease in choline acetyltransferase and increase in glutamic acid decarboxylase apparent activity, respectively. An apparent marked increase in 3H-DA uptake was likewise measured, mainly related to an increase in Vmax. Determination of serotonin (5HT) and 5-hydroxyindole acetic acid (5HIAA) endogenous contents showed in the deafferented striatum a decrease in 5HT concentrations associated with an increase in 5HIAA levels. Taken together, all these changes in neurotransmitter markers suggest that, directly through the thalamostriatal pathway or indirectly, the thalamus can exert a complex influence on striatal cholinergic and GABAergic neuronal functions as well as on the activity of dopaminergic and serotoninergic striatal afferent fibers.