Neurotensin induces calcium oscillations in cultured amacrine cells.
The peptide, neurotensin, is found in a class of amacrine cells synapsing chiefly with other amacrine cells in the chicken retina (Li & Lam, 1990; Watt et al., 1991). To investigate the possible effects of neurotensin, we have used Ca2+ imaging to measure cytosolic Ca2+ concentrations in cultured chick amacrine cells. Following a delay of about 2 min, neurotensin (300 nM) induced oscillations in Ca2+ concentration that typically had a period of 2 min and peak values of about 300 nM when averaged over the cell body. The phospholipase C inhibitors U-73, 112 and 4'-bromophenacyl bromide terminated oscillations induced by neurotensin but the protein kinase inhibitors H7 and staurosporine did not inhibit oscillations, increasing their frequency instead. In the absence of external Ca2+, neurotensin induced only a single Ca2+ transient, much briefer than when external Ca2+ was present. Together these results suggest that neurotensin activates phospholipase C, thereby producing IP3 that triggers Ca2+ release from an internal store. Although this released Ca2+ contributes to periodic Ca2+ peaks, the majority of cytosolic Ca2+, even in the first peak, comes from Ca2+ influx across the plasmalemma.
Borges
S
S
Division of Biological Sciences, University of California, Davis 95616, USA.
Gleason
E
E
Frerking
M
M
Wilson
M
M
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D003600:Cytosol / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors; D004963:Estrenes / Q000494:pharmacology; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009496:Neurotensin / Q000494:pharmacology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D004791:Enzyme Inhibitors; D004963:Estrenes; D019269:Phosphatidylinositol 4,5-Diphosphate; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D009496:Neurotensin; D005680:gamma-Aminobutyric Acid; D010738:Type C Phospholipases; D002118:Calcium