RELEASE OF SECRETONEURIN AND NORADRENALINE FROM HYPOTHALAMIC SLICES AND ITS DIFFERENTIAL INHIBITION BY CALCIUM-CHANNEL BLOCKERS

Secretoneurin is a newly discovered peptide found in high concentratio ns in brain. We have studied the release of secretoneurin and noradren aline from superfused hypothalamic slices from rat brain. Both electri cal stimulation and potassium induced depolarisation released secreton eurin and noradrenaline from these slices in a calcium-dependent manne r. Electrical stimulation caused a preferential release of noradrenali ne when compared to the secretion elicited by high potassium. The time course of secretoneurin release was more protracted than that of nora drenaline. The calcium channel blocker omega-conotoxin inhibited only the electrically induced release of noradrenaline, whereas nifedipine inhibited only that of secretoneurin. These results establish that sec retoneurin is secreted from neurons. Inhibition of this release by nif edipine is consistent with the concept that secretion from large dense core vesicles occurs at sites different from that of small vesicles a nd depends on calcium influx via L-type calcium channels.