Characterization of Voltage-Dependent Ca 2+ Currents in Identified Drosophila Motoneurons In Situ

• Published in: Journal of neurophysiology 2008-08, Vol.100 (2), p.868-878
• Main Authors: Worrell, Jason W., Levine, Richard B.
• Format: Article
• Language: English
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.90464.2008

Voltage-dependent Ca 2+ channels contribute to neurotransmitter release, integration of synaptic information, and gene regulation within neurons. Thus understanding where diverse Ca 2+ channels are expressed is an important step toward understanding neuronal function within a network. Drosophila provides a useful model for exploring the function of voltage-dependent Ca 2+ channels in an intact system, but Ca 2+ currents within the central processes of Drosophila neurons in situ have not been well described. The aim of this study was to characterize voltage-dependent Ca 2+ currents in situ from identified larval motoneurons. Whole cell recordings from the somata of identified motoneurons revealed a significant influence of extracellular Ca 2+ on spike shape and firing rate. Using whole cell voltage clamp, along with blockers of Na + and K + channels, a Ca 2+ -dependent inward current was isolated. The Drosophila genome contains three genes with homology to vertebrate voltage-dependent Ca 2+ channels: Dmca1A, Dmca1D, and Dmα1G. We used mutants of Dmca1A and Dmca1D as well as targeted expression of an RNAi transgene to Dmca1D to determine the genes responsible for the voltage-dependent Ca 2+ current recorded from two identified motoneurons. Our results implicate Dmca1D as the major contributor to the voltage-dependent Ca 2+ current recorded from the somatodendritic processes of motoneurons, whereas Dmca1A has previously been localized to the presynaptic terminal where it is essential for neurotransmitter release. Altered firing properties in cells from both Dmca1D and Dmca1A mutants indicate a role for both genes in shaping firing properties.