Octopamine receptors in the honeybee (Apis mellifera) brain and their disruption by RNA-mediated interference.

Octopamine plays important neuromodulatory roles in the honeybee brain. Accordingly, mRNA from a recently identified honeybee octopamine receptor (AmOA1) is distributed throughout the brain. We have evaluated the occurrence of AmOA1 in the antennal lobe (AL) as well as rest of the brain (RB) by western blotting using an antiserum raised against a peptide selected from AmOA1 sequence. In addition to an expected band (78 kDa in the AL), one additional band (72 kDa) was identified from the AL and four bands (48, 60, 72 and 78 kDa) were observed in the RB. These bands were also recognized with antiserum against a different peptide segment from an octopamine receptor ortholog from the fruitfly (OAMB). Significant sequence identity with the peptide segment used to generate the antiserum was only found with OAMB and its splice variants in fruitfly; it was less conserved in other biogenic amine receptors from honeybee and other insects. Furthermore, western blot analysis performed on brains with dsRNA-treated antennal lobes showed a decrease in the intensity of all four bands. This suggests that AmOA1 antiserum specifically recognizes one or more types of AmOA1 receptors in the honeybee brain. We extend our earlier study of RNAi to quantify the rate of spread of dsRNA from a localized injection to other neuropils.