Growth cones isolated from developing rat forebrain: uptake and release of GABA and noradrenaline.
A growth cone-enriched fraction isolated from neonatal rat forebrain was shown to accumulate gamma-amino [3H]butyric acid ([3H]-GABA) and [3H]noradrenaline ([3H]NA). Uptake of both neurotransmitters was sodium- and temperature-dependent and exhibited saturation kinetics with Km values of 17.7 microM and 4.5 microM respectively and Vmax values of 114 pmol/min/mg protein and 59 pmol/min/mg protein respectively. Electron microscopic autoradiography showed that about 50% of isolated growth cones can accumulate [3H]GABA. Inhibitor studies showed that beta-alanine was a relatively weak inhibitor of [3H]GABA uptake compared to nipecotic acid and diamino-butyric acid. Growth cone fractions preloaded with [3H]GABA and [3H]NA demonstrated a K+ (25 mM) -induced release of both neurotransmitters. Of the K+-stimulated release of [3H]GABA 50% was Ca2+-dependent, whereas the release of [3H]NA was entirely Ca2+-independent.
D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D001921:Brain / Q000254:growth & development / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D018756:GABA Antagonists; D007700:Kinetics; D009474:Neurons / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018756:GABA Antagonists; D011506:Proteins; D005680:gamma-Aminobutyric Acid; D011188:Potassium; D009638:Norepinephrine