Abstract: The effects of cAMP and cGMP on the high-voltage activated (HVA) Ca²⁺ channels in the central neurons isolated from the 3rd instar larvae of the cotton bollworm (Helicoverpa armigera) were studied using the whole cell patch clamp technique. With barium as current carrier, the currents of Ca²⁺ channels were recorded by blocking Na⁺ and K⁺ currents. Extracellular application of 0.1 mmol/L forskolin, a stimulator of adenylyl cyclase (AC), had no effect on the peak amplitude of Ba²⁺ currents. In contrast, 1 mmol/L cGMP in the intracellular solution suppressed the current amplitude significantly and the inhibition was time and dose dependent. The results suggest that the activities of HVA Ca²⁺ channels in the cotton bollworm may not be affected by the elevated cAMP, but can be inhibited by the increased cGMP.

Key words: Helicoverpa armigera, cyclic AMP, cyclic GMP, high-voltage activated calcium channel, patch clamp