Calcium involvement in mediating the action of octopamine and hypertrehalosemic peptides on insect haemocytes

Abstract

Octopamine, the hypertrehalosemic peptides HT‐I and HT‐II and the calcium ionophore A23187 elevate intracellular calcium levels in cultured haemocytes of Malacosoma disstria (Lepidoptera: Lasiocampidae). The octopamine‐mediated response is dose‐dependent and the magnitude of the response is influenced by the concentration of calcium in the incubation medium. Mianserin, an inhibitor of octopamine‐mediated elevation of cyclic AMP production, blocks the octopamine‐mediated increase in intracellular calcium but has no effect on the HT‐I‐ and HT‐II‐mediated responses. The results indicate that some effects of octopamine are mediated through agonist‐dependent calcium gating whereas others are expressed through receptors coupled to adenylate cyclase. The study also confirms previous suggestions that HT‐I and HT‐II elevate intracellular calcium concentrations.