4-Chloro-3-hydroxyanthranilate inhibits quinolinate production in the rat hippocampus in vivo.

Quinolinic acid (QUIN) is a potential pathogen in a variety of excitotoxic and neuroviral brain diseases. In the present study, the ability of the QUIN synthesis inhibitor 4-chloro-3-hydroxyanthranilic acid to attenuate the production of QUIN was assessed in the hippocampus of awake rats. To this end, QUIN's immediate bioprecursor 3-hydroxyanthranilic acid (30 microM) was applied through a microdialysis probe, and QUIN production was monitored hourly in the perfusate. After 3 h, 4-chloro-3-hydroxyanthranilic acid (3 microM-3 mM) was included in the perfusion medium, and dialysis was continued for another 3 h. The drug caused dose-dependent inhibition of QUIN neosynthesis, with an apparent IC50 value of 32 microM. Discontinuation of drug administration, with continued perfusion of 3-hydroxyanthranilic acid, revealed that the drug effect was reversible. Intravenous application of 4-chloro-3-hydroxyanthranilic acid (14 mg/kg) resulted in a significant decrease in extracellular QUIN, reaching a nadir of 67% of saline-treated controls after 3 h. The data indicate that both intracerebral and systemic administration of 4-chloro-3-hydroxyanthranilic acid effectively interferes with QUIN production in the rat brain. The results suggest that QUIN synthesis inhibitors such as 4-chloro-3-hydroxyanthranilic acid may become of value in brain diseases that are caused by hyperphysiological quantities of QUIN.