Résumé
The effects of galanin on secretion and cytosolic free Ca
2+ concentration ([Ca
2+
i) have been studied in GH3/B6 pituitary cells. Prolactin (PRL) and growth hormone (GH) release was measured in column Perifusion experiments; [Ca
2+]
i was monitored in single cells by dual emission microspectrofluorimetry using indo-1 as intracellular Ca
2+ probe. Galanin (0.1–1 nM) caused PRL and GH release coincident with a modest rise in [Ca
2+]
i The increase in [Ca
2+]
i comprises the establishment of characteristic long-lasting bursts of [Ca
2+]
i transients. Galanin acts on Ca
2+ entry through voltage-gated Ca
2+ channels since there was no response to the peptide when Cd
2+ - a Ca
2+ channel blocker - was added to the bath solution. The stimulation of bursting activity by galanin may provide a fine Ca
2+ -signalling mechanism which maximally stimulates hormone release while avoiding refractory periods.