Putrescine modulation of depolarization-induced [3H]serotonin release from fish brain synaptosomes.
In this study, we investigated the effects of putrescine, a precursor of polyamine metabolism, on depolarization (potassium chloride, KCl)-induced [3H]serotonin (5-hydroxytryptamine (5-HT)) release from brain synaptosomes of rainbow trout (Oncorhynchus mykiss). An irreversible inhibitor of polyamine metabolism, difluoromethyl-ornithine (DFMO), inhibited the KCl-induced [3H]serotonin efflux, and addition of putrescine (PUT) reversed the inhibitory effects of the former in synaptosomal preparations. In Fura-2/AM loaded synaptosomes, KCl stimulated Ca2+ influx. Hence, prior addition of EGTA abolished the KCl-induced Ca2+ responses, indicating that KCl-induced depolarization recruited Ca2+ from extracellular medium. The DFMO curtailed the KCl-evoked Ca2+ influx, and addition of PUT reversed the inhibitory effects of DFMO. Furthermore, fish brain was found to contain polyamines in high amounts (e.g. putrescine from 600 +/- 20 to 850 +/- 30 nmol/g protein). These results suggest that polyamine putrescine, present in fish brain, might be involved in [3H]serotonin efflux via Ca2+ influx mechanisms.
Khan
N A
NA
Laboratoire de Physiologie Animale, Université de Limoges, France.
Moulinoux
J P
JP
Deschaux
P
P
D000818:Animals; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D000518:Eflornithine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005071:Evoked Potentials / Q000502:physiology; D016257:Fura-2; D008564:Membrane Potentials / Q000187:drug effects; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010802:Phylogeny; D011189:Potassium Chloride / Q000494:pharmacology; D011700:Putrescine / Q000032:analysis / Q000494:pharmacology*; D012701:Serotonin / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013574:Synaptosomes / Q000378:metabolism*; D014316:Tritium
D004791:Enzyme Inhibitors; D014316:Tritium; D012701:Serotonin; D011189:Potassium Chloride; D002118:Calcium; D016257:Fura-2; D011700:Putrescine; D000518:Eflornithine