Honeybee locomotion is impaired by Am-Ca V 3 low voltage-activated Ca 2+ channel antagonist.

Voltage-gated Ca2+ channels are key transducers of cellular excitability and participate in several crucial physiological responses. In vertebrates, 10 Ca2+ channel genes, grouped in 3 families (CaV 1, CaV 2 and CaV 3), have been described and characterized. Insects possess only one member of each family. These genes have been isolated in a limited number of species and very few have been characterized although, in addition to their crucial role, they may represent a collateral target for neurotoxic insecticides. We have isolated the 3 genes coding for the 3 Ca2+ channels expressed in Apis mellifera. This work provides the first detailed characterization of the honeybee T-type CaV 3 Ca2+ channel and demonstrates the low toxicity of inhibiting this channel. Comparing Ca2+ currents recorded in bee neurons and myocytes with Ca2+ currents recorded in Xenopus oocytes expressing the honeybee CaV 3 gene suggests native expression in bee muscle cells only. High-voltage activated Ca2+ channels could be recorded in the somata of different cultured bee neurons. These functional data were confirmed by in situ hybridization, immunolocalization and in vivo analysis of the effects of a CaV 3 inhibitor. The biophysical and pharmacological characterization and the tissue distribution of CaV 3 suggest a role in honeybee muscle function.