Kynurenic acid (KYNA) is a tryptophan metabolite that is synthesized and released by astrocytes and acts as a competitive antagonist of the glycine site of N-methyl-D-aspartate receptors at high concentrations and as a noncompetitive antagonist of the alpha7-nicotinic acetylcholine receptor at low concentrations. The discovery of increased cortical KYNA levels in schizophrenia prompted the hypo...

We have previously demonstrated that general anesthesia with 1.2% isoflurane-70% nitrous oxide impairs acquisition of a radial arm maze task in both young and aged rats when testing begins 2 days after anesthesia and in aged rats when testing begins 2 wk later. We designed this study to examine whether postanesthesia learning impairment is persistent in young rats. Six-month-old rats were rando...

Pigeons, unlike rats, do not display very accurate spatial working memory when tested in the traditional radial arm maze apparatus unless they are given special and extended training (cf. Roberts & Van Veldhuizen, 1985). One possible reason for their apparent "unpreparedness" to display spatial memory abilities in radial arm mazes is that, in the wild, pigeons tend to feed in open-field environ...