Regional calcium regulation within cultured Drosophila neurons: effects of altered cAMP metabolism by the learning mutations dunce and rutabaga.
The dunce (dnc) and rutabaga (rut) mutations of Drosophila affect a cAMP-dependent phosphodiesterase and a Ca(2+)/CaM-regulated adenylyl cyclase, respectively. These mutations cause deficiencies in several learning paradigms and alter synaptic transmission, growth cone motility, and action potential generation. The cellular phenotypes either are Ca(2+) dependent (neurotransmission and motility) or mediate a Ca(2+) rise (action potential generation). However, interrelations among these defects have not been addressed. We have established conditions for fura-2 imaging of Ca(2+) dynamics in the "giant" neuron culture system of Drosophila. Using high K(+) depolarization of isolated neurons, we observed a larger, faster, and more dynamic response from the growth cone than the cell body. This Ca(2+) increase depended on an influx through Ca(2+) channels and was suppressed by the Na(+) channel blocker TTX. Altered cAMP metabolism by the dnc and rut mutations reduced response amplitude in the growth cone while prolonging the response within the soma. The enhanced spatial resolution of these larger cells allowed us to analyze Ca(2+) regulation within distinct domains of mutant growth cones. Modulation by a previous conditioning stimulus was altered in terms of response amplitude and waveform complexity. Furthermore, rut disrupted the distinction in Ca(2+) responses observed between the periphery and central domain of growth cones with motile filopodia.
Berke
Brett
B
Interdisciplinary Program in Neuroscience and Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242, USA.
Wu
Chun-Fang
CF
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004330:Drosophila; D004558:Electric Stimulation; D005456:Fluorescent Dyes; D016257:Fura-2; D020439:Growth Cones / Q000378:metabolism* / Q000648:ultrastructure; D007858:Learning / Q000502:physiology*; D009154:Mutation; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism; D011930:Reaction Time / Q000502:physiology; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D005456:Fluorescent Dyes; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin; D000242:Cyclic AMP; D011188:Potassium; D002118:Calcium; D016257:Fura-2