The release of [3-H]gamma-aminobutyric acid and neurophysin from the isolated rat posterior pituitary.
The efflux of [3-H]GABA from glial cells in the rat posterior pituitary was followed in isolated glands incubated in the presence of 10-minus 5 M aminooxyacetic acid which is known to inhibit GABA metabolism. Electrical stimulation of the pituitary stalk evoked an increase in the rate of efflux of [3-H]GABA as did elevation of the extracellular potassium concentration. The release of neurophysin from nerve terminals in the gland was also increased by electrical stimulation. The increase in [3-H]GABA efflux appeared to be independent of frequency at 2, 5, or 25 HZ if the number of pulses delivered was kept constant, although stimulation at 10 HZ was more effective than either 2 or 25 HZ. The efflux of [3-H]GABA evoked by 56 mM K+ was inhibited by 50% when calcium was removed from the washing fluid and 3 mM EGTA added, while the response evoked by electrical stimulation was unaffected by this procedure. The electrically induced efflux of [3-H]GABA was inhibited by 50% when choline chloride was substituted for sodium chloride in the washing medium, although it was unaffected by tetrodotoxin (0.8 times 10-minus 6 g/ml). The release of exogenous GABA from the pituicyte glia is compared with that of neurophysin from the nerve terminals in the posterior pituitary, and the results are discussed with reference to possible mechanisms of the glial release process.
D000613:Aminobutyrates / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002794:Choline / Q000502:physiology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009481:Neurophysins / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000201:enzymology / Q000378:metabolism*; D011188:Potassium / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology; D013268:Stimulation, Chemical; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D000613:Aminobutyrates; D009481:Neurophysins; D014316:Tritium; D012965:Sodium Chloride; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D002794:Choline; D011188:Potassium; D002118:Calcium