Figure 1.
Chiral selectivity of the “C” neuron of maxillary palp basiconic sensilla.
(A) Spontaneous activity of neurons associated with a basiconic sensillum on the maxillary palp of a female Ae. aegypti. Note the presence of three spike heights: A = largest spike is responsive to CO2, B = intermediate spike, and C = smallest amplitude spike is reliably activated by (R)-(−)-1-octen-3-ol. Response of “C” neuron is to a low dose of (R)-(−)-1-octen-3-ol. (B) Structure of enantiomers of 1-octen-3-ol: (R)-(−)-1-octen-3-ol and (S)-(+)-1-octen-3-ol. (C) Electrophysiological responses from an individual basiconic sensillum to a 1 sec exposure to increasing stimulus loads of the enantiomers of 1-octen-3-ol. Note at higher loads of (R)-(−)-1-octen-3-ol spikes from “C” neuron are not easily discerned from baseline. (D) Dose-response curves constructed from mean responses of “C” neurons to increasing stimulus loads of racemic 1-octen-3-ol (Rac-1-octen-3-ol, n = 4)), and its component enantiomers, (R)-(−)-1-octen-3-ol (n = 5), and (S)-(+)-1-octen-3-ol (n = 4). Points represented are mean ± SEM.
Figure 2.
(R)-(−)-1-octen-3-ol strongly preferred over related analogs.
Dose-response relationships from the “C” neuron in maxillary palp sensilla of female Ae. aegypti in response to increasing doses of (R)-(−)-1-octen-3-ol (n = 5) and structurally similar chemicals. (A) Movement of chiral center from “3” to “4” position, 1-octen-4-ol (n = 4). (B) Changes in carbon chain length: 1-hepten-3-ol (n = 4) and 1-nonen-3-ol (n = 3). (C) Change in functional group with loss of chiral center, 1-octen-3-one (n = 4). (D) Saturation of double bond, 3-octanol (n = 4). Points represented are mean ± SEM.
Figure 3.
2-Undecanone, a known repellent, activates the “C” neuron.
(A) Dose-response relationship from the “C” neuron in maxillary palp sensilla of female Ae. aegypti in response to increasing doses of (R)-(−)-1-octen-3-ol (n = 5) and 2-undecanone (n = 6). (B) Electrophysiological responses from an individual basiconic sensillum on the maxillary palp of a female Ae. aegypti to a 1 sec exposure to: 1. hexane solvent, 2. 2-undecanone 5000 µg, 3. DEET 5000 µg, and 4. (R)-(−)-1-octen-3-ol 0.05 µg. (C) Mean number of spikes (±SEM; n = 5) from “C” neurons of female Ae. aegypti basiconic sensilla to stimulation with 5000 µg doses of hexanes, 2-undecanone, DEET, IR3535, picaridin and to 0.05 µg dose of (R)-(−)-1-octen-3-ol. Points represented are mean ± SEM. “A”, “B”, and “C” with arrows designate three spike classes present in recordings from the basiconic sensilla.