Storage of biogenic amines in guinea-pig brain synaptosomes: influence of proton gradient and membrane potential.
1 The effects of K(+), NaCN and the ionophores monensin, nonactin and carbonyl-cyanide-p-trifluoro-methoxyphenylhydrazone (FCCP) on the contents of [(3)H]-5-hydroxytryptamine ([(3)H]-5-HT), [(3)H]-dopamine and [(3)H]-noradrenaline ([(3)H]-NA) in guinea-pig synaptosomes preloaded with these amines were measured.2 In the presence of Ca(2+), K(+) markedly reduced the amine content of the synaptosomes, indicating an acceleration of spontaneous amine release. In the absence of Ca(2+), K(+) had much less effect.3 Monensin, nonactin and FCCP caused a release of all the three labelled amines. This release was considerably faster and more marked than that induced by K(+) and showed no dependence on Ca(2+). The ionophores did not release lactate-dehydrogenase from synaptosomes.4 NaCN, a blocker of oxidative energy production, did not enhance the spontaneous release of [(3)H]-5-HT nor did it influence the monensin-induced release of [(3)H]-5-HT.5 It is concluded that (a) the intragranular storage of 5-HT, dopamine and NA is dependent on the maintenance of a pH-gradient across the granular membrane as well as on the granular membrane potential; (b) the ionophores cause a non-exocytotic release of granular amines, and (c) blood platelets are partial models for aminergic brain neurones as far as intragranular amine storage is concerned.
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001679:Biogenic Amines / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D018942:Macrolides; D008564:Membrane Potentials; D008985:Monensin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011522:Protons; D013574:Synaptosomes / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D001679:Biogenic Amines; D018942:Macrolides; D011522:Protons; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D008985:Monensin; D007770:L-Lactate Dehydrogenase; D011188:Potassium; D002118:Calcium; C050476:nonactin