title: Oral administration of glycine increases extracellular serotonin but not dopamine in the prefrontal cortex of rats.
abstract: OBJECTIVE
  Glycine, one of the non-essential amino acids, has been reported to be effective in reducing negative symptoms of schizophrenia. Recently, we found that glycine improves subjective sleep quality in humans. The aim of this study was to investigate the effects of oral glycine administration on endogenous 5-hydroxytryptamine (5-HT) and dopamine in the prefrontal cortex (PFC) of living rats.
  
  
  METHODS
  Microdialysis probes were inserted stereotaxically into the rat prefrontal cortex. Cortical levels of 5-HT and dopamine were measured following oral administration of 1 or 2 g/kg glycine, 2 g/kg d-serine, or 2 g/kg L-serine.
  
  
  RESULTS
  Both glycine and d-serine significantly increased extracellular 5-HT levels for 10 min, whereas dopamine levels remained unchanged. L-serine, in contrast, had no significant effects on 5-HT levels.
  
  
  CONCLUSIONS
  It is possible that the increase in 5-HT in response to glycine and d-serine was mediated by N-methyl-D-aspartate receptors. The transient increase in 5-HT in the PFC might be associated with the alleviation of negative symptoms in patients with schizophrenia and the amelioration of sleep quality in patients with insomnia.
authors.affiliation: Research Institute for Health Fundamentals, Ajinomoto Co., Inc., Kanagawa, Japan. makoto_bannai@ajinomoto.com
authors.forename: Makoto
authors.initials: M
authors.lastname: Bannai
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kawai
authors.forename: Kenji
authors.initials: K
authors.lastname: Nagao
authors.forename: Sayako
authors.initials: S
authors.lastname: Nakano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Matsuzawa
authors.forename: Eiji
authors.initials: E
authors.lastname: Shimizu
mesh_terms: D000284:Administration, Oral; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D005998:Glycine / Q000008:administration & dosage / Q000134:cerebrospinal fluid / Q000494:pharmacology*; D008297:Male; D017551:Microdialysis; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000008:administration & dosage / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism*
chemical_list: D012701:Serotonin; D012694:Serine; D005998:Glycine; D004298:Dopamine