Abstract: Using Ba²⁺as current carrier, the effect of G proteins on the highvoltage sensitive Ca²⁺ channels in the central neurons isolated from the 3rd instar larvae of the cotton bollworm Helicoverpa armigera was studied with the whole cell patch clamp technique. The results indicated that the inclusion of guanosine 5'-O-(3-thiotriposate) (GTPγS, 2 mmol/L) in the pipette solution prevented the decline in peak current, and (95.99±7.93)% of the initial current was remained by the end of 20 min recording, compared with (72.09±12.80)% in the control (P <0.01). Moreover, I-V relationship curve obtained from neurons treated with GTP Γs shifted to the positive voltage. In contrast, guanosine5 '-O-(2- thiophosphate) (GDPβS, 2 mmol/L) in the intracellular solution reduced the peak current to (41.95±9.32)% of the initial value, significantly lower than that in the control (P<0.01). No obvious shift of the I-V relationship curve was caused by GDPβS. The results showed that the activities of calcium channels were influenced by GTPγS and GDPβS, which suggests that current amplitude and voltage dependence of calcium channels in H. armigera are modulated by G proteins.

Key words: Helicoverpa armigera, GTP analogue, GDP analogue, highvoltage sensitive, calcium channel, patch clamp 