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The Journal of Neuroscience, February 15, 1998, 18(4):1399-1407
Outward Currents in Drosophila Larval Neurons:
dunce Lacks a Maintained Outward Current Component
Downregulated by cAMP
Ricardo
Delgado2,
Ronald
Davis3,
Maria Rosa
Bono1,
Ramon
Latorre1, 2 and
Pedro
Labarca1, 2
1 Departamento de Biologia, Facultad de Ciencias,
Universidad de Chile, 2 Centro de Estudios Cientificos de
Santiago, Casilla 16443, Santiago 9, Chile, and 3 Division
of Neuroscience, Department of Cell Biology, Baylor College of
Medicine, Houston, Texas 77030
Outward current modulation by cAMP was investigated in wild type
(wt) and dunce (dnc)
Drosophila larval neurons. dnc is
deficient in a cAMP phosphodiesterase and has altered memory. Outward
current modulation by cAMP was investigated by acute or chronic
exposure to cAMP analogs. The analysis included a scrutiny of outward
current modulation by cAMP in neurons from the mushroom bodies (mrb). In Drosophila, the mrb are the centers of olfactory
acquisition and retention. Based on outward current patterns, neurons
were classified into four types. Downmodulation of outward currents induced by acute application of cAMP analogs was reversible and found
only in type I and type IV neurons. In the general wt neuron population, approximately half of neurons exhibited cAMP-modulated, 4-aminopyridine (4-AP)-sensitive currents. On the other hand, a
significantly larger fraction of mrb neurons in wt (70%) was endowed
with cAMP-modulated, 4-AP-sensitive currents. Only 30% of the
dnc neurons displayed outward currents modulated by
cAMP. The deficit of cAMP-modulated outward currents was most severe in
neurons derived from the mrb of dnc individuals. Only
4% of the mrb neurons of dnc were cAMP-modulated. The
dnc defect can be induced by chronic exposure of wt
neurons to cAMP analogs. These results document for the first time a
well defined electrophysiological neuron phenotype in correlation with
the dnc defect. Moreover, this study demonstrates that
in dnc mutants such a deficiency affects most severely
neurons in brain centers of acquisition and retention.
Key words:
Drosophila; neurons; outward currents; cAMP; downmodulation; mushroom bodies; dunce mutants
Copyright © 1998 Society for Neuroscience 0270-6474/98/1841399-09$05.00/0
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