Response and adaptation to analogs of disparlure by specialist antennal receptor neurons of gypsy moth, Lymantria dispar

Reception and adaptation of antennal receptors in response to (+)-disparlure [(+)-D], the sex attractant pheromone of the gypsy moth, Lyman tria dispar-(Lepidoptera: Lymantriidae)], its enantiomer, (-)-D, and analogs of disparlure in which the epoxide group is replaced with various three-membered rings [(+/-)-cyclopropyl (2HC), (+/-)-difluorocyclopropyl (2FC), (+/-)-dichlorocyclopropyl (2ClC), and (+/-)-aziridinyl (AZ), (+)-AZ, and (-)AZ] as well as a mixture of 1,1-epoxy analogs were investigated using electroantennograms. Antennal receptors of male moths were more responsive (5 mu g stimulus load) to (+)-D than to (-)-D; while responses to each of the analogs were significantly less and did not differ from each other. Antennal receptors of female moths did not respond significantly to any of the compounds at this stimulus load. Dose-response curves revealed greater sensitivity of male antennae to (+)-D than (-)-D. Among the cyclopropane analogs and 1,1-epoxy mixture (1,IE), the order of sensitivity was: 2FC > 2ClC > 2HC > 1,1E. Antennae were least sensitive to the aziridinyl analogs; however, (+)-AZ was more active than (-)-AZ, while an intermediate response was elicited by the racemate. Males exposed to (+)-D adapted to (+)-D, while responses to (+)-D were not significantly affected by exposure to (-)-D, 2FC or (+)-AZ. After exposure to hexylacetate, males showed adaptation to (+)D or (-)-D, but not to the other odorants. Preliminary field data correlate well with knowledge obtained in our electrophysiological studies and demonstrate the usefulness of such studies. These results indicate that novel approaches to the design and synthesis of potential agonists of disparlure receptors are necessary before substantial effects on the activity of disparlure are realized.