The Journal of Neuroscience, June 1, 2002, 22(11):4437-4447
Regional Calcium Regulation within Cultured
Drosophila Neurons: Effects of Altered cAMP Metabolism
by the Learning Mutations dunce and
rutabaga
Brett
Berke1 and
Chun-Fang
Wu1, 2
1 Interdisciplinary Program in Neuroscience and
2 Department of Biological Sciences, University of Iowa,
Iowa City, Iowa 52242
The dunce (dnc) and
rutabaga (rut) mutations of
Drosophila affect a cAMP-dependent phosphodiesterase and
a Ca2+/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 Ca2+
dependent (neurotransmission and motility) or mediate a
Ca2+ rise (action potential generation). However,
interrelations among these defects have not been addressed. We have
established conditions for fura-2 imaging of Ca2+
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
Ca2+ increase depended on an influx through
Ca2+ 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 Ca2+ 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 Ca2+ responses observed between the
periphery and central domain of growth cones with motile filopodia.
Key words:
learning and memory; dnc; rut; fura-2; Ca2+ dynamics; neuronal culture; growth cone; cAMP
Copyright © 2002 Society for Neuroscience 0270-6474/02/22114437-11$05.00/0
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