GALANIN EVOKES A CYTOSOLIC CALCIUM BURSTING MODE AND HORMONE-RELEASE IN GH3/B6 PITUITARY-CELLS

The effects of galanin on secretion and cytosolic free Ca2+ concentration ([Ca2+]i) have been studied in GH3/B6 pituitary cells. Prolactin (PRL) and growth hormone (GH) release was measured in column perifusion experiments; [Ca2+]i was monitored in single cells by dual emission microspectrofluorimetry using indo-1 as intracellular Ca2+ probe. Galanin (0.1-1 nM) caused PRL and GH release coincident with a modest rise in [Ca2+]i. The increase in [Ca2+]i comprises the establishment of characteristic long-lasting bursts of [Ca2+]i transients. Galanin acts on Ca2+ entry through voltage-gated Ca2+ channels since there was no response to the peptide when Cd2+ - a Ca2+ channel blocker - was added to the bath solution. The stimulation of bursting activity by galanin may provide a fine Ca2+-signalling mechanism which maximally stimulates hormone release while avoiding refractory periods.