Honeybee locomotion is impaired by Am-Ca3 low voltage-activated Ca channel antagonist.

Voltage-gated Ca channels are key transducers of cellular excitability and participate in several crucial physiological responses. In vertebrates, 10 Ca channel genes, grouped in 3 families (Ca1, Ca2 and Ca3), 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 Ca channels expressed in Apis mellifera. This work provides the first detailed characterization of the honeybee T-type Ca3 Ca channel and demonstrates the low toxicity of inhibiting this channel. Comparing Ca currents recorded in bee neurons and myocytes with Ca currents recorded in Xenopus oocytes expressing the honeybee Ca3 gene suggests native expression in bee muscle cells only. High-voltage activated Ca 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 Ca3 inhibitor. The biophysical and pharmacological characterization and the tissue distribution of Ca3 suggest a role in honeybee muscle function.