Dopamine enhances Ca2+ responses in synaptic terminals of retinal bipolar neurons.
The effect of dopamine on depolarization-induced Ca2+ influx was studied using the fluorescent Ca2+ indicator fura-2 in synaptic terminals of bipolar neurons from gold-fish retina. Dopamine reversibly enhanced the rise in intracellular Ca2+ elicited by elevated external potassium. The enhancement was slowly reversible. The effect of dopamine was mimicked by forskolin and CPT-cAMP, a membrane-permeant analog of cAMP. However, 1,9-dideoxyforskolin, a forskolin analog that does not activate adenylyl cyclase, was ineffective. This suggests that dopamine, via cAMP, regulates the rise in presynaptic Ca2+ concentration in response to depolarization, potentially enhancing transmitter release.
Heidelberger
R
R
Department of Neurobiology and Behavior, State University of New York, Stony Brook 11794-5239.
Matthews
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology; D004298:Dopamine / Q000494:pharmacology*; D016257:Fura-2; D006054:Goldfish / Q000378:metabolism*; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010786:Photoreceptor Cells / Q000187:drug effects; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism; D012160:Retina / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000378:metabolism
D005576:Colforsin; D000242:Cyclic AMP; D002118:Calcium; D016257:Fura-2; D004298:Dopamine