Transport of quinolinic acid into rabbit and rat brain.

The transport metabolism of [3H]quinolinic acid in the central nervous system of rabbits and rats were studied. In vitro [3H]quinolinic acid was not readily accumulated by isolated choroid plexus. After the intraventricular injection of tracer quantities of [3H]quinolinic acid, the [3H]quinolinic acid did not enter the brain as readily as concurrently injected [14C]mannitol and was not metabolized. The permeability-surface area constant for [3H]quinolinic acid at the rat blood-brain barrier was 1.5 +/- 1.3 X 10(-5) sec-1 compared to 2.8 +/- 0.4 X 10(-5) sec-1 for [3H]mannitol. Our results suggest that: 1) [3H]quinolinic acid is transported in the CNS by passive diffusion and 2) is not metabolized.