title: Time-dependent effect of GABA on glucose-stimulated insulin secretion from isolated islets in rat.
abstract: OBJECTIVE
  Gamma-amino butyric acid (GABA) is an inhibitory neurotransmitter found widely in the central nervous system and some peripheral tissues such as the islets of pancreas. The aim of this study was to determine the time dependency of the effect of GABA on glucose-stimulated insulin secretion in isolated islets of rats.
  
  
  METHODS
  The collagenase digestion technique was used to isolate the islets from pancreata of male Wistar rats (200-250 g). Insulin secretion was assessed in islets exposed to different concentrations of glucose (8.3 and 16.7 mM), in the presence or absence of GABA (50 µM), for different incubation times and also pre-incubation of islets with GABA, 30 and 45 min before 8.3 mM glucose stimulation. Furthermore insulin secretion with different concentrations of glucose (8.3 and 16.7 mM), and in the presence or absence of different concentrations of baclofen, a GABA(B) agonist and of saclofen, a GABA(B) antagonist during 1 h of incubation was assessed. Insulin release was reported as mean ± SE μU/islet/min and p values of <0.05 were considered significant.
  
  
  RESULTS
  GABA with concentration of 50 µM inhibited the glucose stimulated insulin secretion during a 60 min incubation period. Baclofen had no significant effect on glucose-induced insulin secretion, while saclofen (100 µM) significantly increased 16.7 mM glucose-induced insulin secretion in 60 min of incubation (p < 0.05). Pre-incubation of islets with GABA for 45 min, before glucose stimulation, increased glucose-induced insulin secretion.
  
  
  CONCLUSIONS
  GABA could have both stimulatory and inhibitory effects on glucose-stimulated insulin secretion, depending on the time of exposure and glucose concentration.
authors.affiliation: Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Faraji
authors.forename: Asghar
authors.initials: A
authors.lastname: Ghasemi
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Motamedi
authors.forename: Saleh
authors.initials: S
authors.lastname: Zahediasl
mesh_terms: D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives / Q000494:pharmacology; D058786:GABA-B Receptor Agonists / Q000494:pharmacology; D058788:GABA-B Receptor Antagonists / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology / Q000502:physiology*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
chemical_list: D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D007328:Insulin; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D005947:Glucose; C080629:saclofen