ACIDIC AMINO-ACID ACCUMULATION BY RAT CHOROID-PLEXUS DURING DEVELOPMENT

Acidic amino acid accumulation by the choroid plexuses of the lateral ventricles was investigated using 1, 2, 3 week and adult (7-10 weeks o ld) rats. The accumulation from both blood and CSF sides of the choroi d plexuses were investigated. The uptake from blood side was studied u sing the bilateral in situ brain perfusion, and time-dependent uptake profiles (2, 10, 20, and 30 min) of C-14-labelled aspartate, glutamate , and NMDA were measured. [H-3]Mannitol was also included in perfusion fluid as a baseline for [C-14]amino acid uptake into choroidal tissue . Uptake of [C-14]aspartate and [C-14]glutamate declined with age, whi le [C-14]NMDA showed no significant uptake at any age. Twenty min [3H] mannitol uptake in the 1-week-old rat was significantly greater than t he adult (P < 0.05). The K-m for [C-14]aspartate and [C-14]glutamate o btained from multiple time uptake profiles also showed reduction with development but it was greater than that for mannitol. [C-14]Aspartate declined from 69.8 +/- 21.1 mu l.min(-1).g(-1) in the neonate to 40.6 +/- 4.0 mu l.min(-1).g(-1) in the adult (P < 0.05), while glutamate s howed a sharper decline from 78.9 +/- 24.2 mu l.min(-1).g(-1) to 17.7 +/- 5.4 mu l.min(-1).g(-1) (P < 0.01). Accumulation of 14C-labelled as partate and glutamate by the choroid plexus from CSF side was also mea sured using ventriculo-cisternal perfusion. The accumulation in the ad ult was found to be 2-3 times greater than that in the neonatal rat (P < 0.05) for both amino acids. The uptake from either side was found t o be saturable, stereospecific, not inhibited by neutral amino acid an alogues, and shared by both aspartate and glutamate. (C) 1997 Elsevier Science B.V.