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During early brain development, N-methyl-d-aspartate (NMDA) receptors are involved in cell migration, neuritogenesis, axon guidance and synapse formation, but the mechanisms which regulate NMDA receptor density and function remain unclear. The kynurenine pathway of tryptophan metabolism includes an agonist (quinolinic acid) and an antagonist (kynurenic acid) at NMDA receptors and we have previously shown that inhibition of the pathway using the kynurenine-3-monoxygenase inhibitor Ro61-8048 in late gestation produces rapid changes in protein expression in the embryos and effects on synaptic transmission lasting until postnatal day 21 (P21). The present study sought to determine whether any of these effects are maintained into adulthood. After prenatal injections of Ro61-8048 the litter was allowed to develop to P60 when some offspring were euthanized and the brains removed for examination. Analysis of protein expression by Western blotting revealed significantly reduced expression of the GluN2A subunit (32%) and the morphogenetic protein sonic hedgehog (31%), with a 29% increase in the expression of doublecortin, a protein associated with neurogenesis. No changes were seen in mRNA abundance using quantitative real-time polymerase chain reaction. Neuronal excitability was normal in the CA1 region of hippocampal slices but paired-pulse stimulation revealed less inhibition at short interpulse intervals. The amount of long-term potentiation was decreased by 49% in treated pups and recovery after low-frequency stimulation was delayed. The results not only strengthen the view that basal, constitutive kynurenine metabolism is involved in normal brain development, but also show that changes induced prenatally can affect the brains of adult offspring and those changes are quite different from those seen previously at weaning (P21). Those changes may be mediated by altered expression of NMDAR subunits and sonic hedgehog., (Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.)

Chloramphenicol a potent inhibitor of bacterial and some mammalian cell protein synthesis, was administered i.p. to a group of mice for 6 consecutive days. Another group of animals was treated similarly with thiamphenicol and a third group served as control. The effects of the two antibiotics on the activity of some liver enzymes; the two pyridoxal 5-phosphate dependent enzymes, kynurenine hydrolase and kynurenine amino-transferase; pyridoxal phosphokinase; beta-glucuronidase and acid ribonuclease were determined. Chloramphenicol and thiamphenicol decreased significantly the activities of kynurenine hydrolase, beta-glucuronidase and acid ribonuclease and both drugs increased the activity of pyridoxal phosphokinase significantly. Their effect on kynurenine amino-transferase was different, chloramphenicol decreased while thiamphenicol increased the enzyme activity. Results are discussed and possible explanations suggested.

L-glycine (1-12.5 micrograms, intracerebroventricularly, i.c.v.) completely prevented seizures induced by i.c.v. administration of L-kynurenine, and practically did not modify those induced by another convulsant quinolinic acid, a metabolite of tryptophan, and by strychnine. L-Glycine administered intraperitoneally (i.p.) (1000 mg/kg) decreased lethality after K-kynurenine and quinolinic acid; at doses of 3000 and 4000 mg/kg which are sedative and hypothermic it prolonged the latency of strychnine and L-kynurenine seizures. The convulsant action of pentylenetetrazol was not modified. Kynurenine seizures are suggested to be related to the action of kynurenine on glycine receptors in the central nervous system.