Role of Extracellular Ca2+ and Calcium Channel Activated by a G Protein-Coupled Receptor Regulating Pheromone Production in Helicoverpa zea (Lepidoptera: Noctuidae)

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Abstract
The physiological action of pheromone biosynthesis activating neuropeptide (PBAN) on isolated pheromone glands of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) was investigated with regard to the role of the Ca2+ channel in stimulating pheromone biosynthesis. A dose–response profile indicated that the minimum level of PBAN stimulation was achieved at 10-11 M. PBAN activity requires the influx of extracellular Ca2+. A time delay of up to 7.5 min from receptor activation by PBAN and influx of extracellular Ca2+ was determined. These results indicate that activation of the PBAN-receptor maintains the activation of a Ca2+ channel for a period of time. Similar results were found using transfected Sf9 cells expressing the cloned PBAN-receptor. This indicates that the Sf9 cells have a Ca2+ channel that is coupled to the receptor in a similar way as in the pheromone gland cells. To determine the type of Ca2+ channel, isolated glands were incubated with PBAN and organic Ca2+ channel blockers. L-type voltage-gated Ca2+ or nonselective Ca2+ channel blockers did not inhibit pheromone production. However, quinidine, a potassium channel blocker, inhibited pheromone production. These results indicate that the receptor-activated Ca2+ channel in the pheromone gland may not be a voltage-activated Ca2+ channel but rather a nonselective ion channel. Our results provide further insight into the action of PBAN with regard to the Ca2+ channel in the signal transduction of pheromone biosynthesis in moths.