Inhibitory and excitatory effects of iodobenzene on the antennal benzoic acid receptor cells of the female silk moth Bombyx mori L.
As shown in single-sensillum recordings, iodobenzene has a bimodal effect on the receptor cell tuned to benzoic acid (BA) of the female silk moth Bombyx mori. Exposure to iodobenzene causes an inhibition of the response to BA. With stimulation by iodobenzene alone, a reduction of basic nerve impulse firing during exposure is followed by a transient post-stimulus excitation (rebound). We suggest that inhibition suppresses excitation during exposure but fades afterwards more rapidly than excitation. Due to the spatial equivalence of the iodine and the acid residue, these effects might indicate opposing interactions of iodobenzene with the specific site for the key compound BA. This is supported by the fact that substitutions by smaller halogens are less effective in both inhibition and rebound. The inhibitory effect but not the rebound with iodobenzene alone was also observed in receptor cells tuned to key compounds other than benzoic acid, e.g. in the cell most sensitive to 2,6-dimethyl-5-heptene-2-ol (DMH-cell) occurring in the same sensillum as the BA-cell, or in the bombykol- and bombykal-cells of the male. At least in these cells the inhibitory effect might reflect the action of iodobenzene on a general site, e.g. the lipid matrix of the plasma membrane of the receptor cells.
de Brito Sanchez
María Gabriela
MG
Laboratorio de Fisiología de Insectos, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina. debrito@cict.fr
Kaissling
Karl-Ernst
KE
D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D001554:Benzene / Q000737:chemistry / Q000494:pharmacology; D019817:Benzoic Acid / Q000494:pharmacology*; D012831:Bombyx / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D006219:Halogens / Q000737:chemistry; D007462:Iodobenzenes / Q000494:pharmacology*; D008297:Male; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000502:physiology; D018035:Receptors, Odorant / Q000187:drug effects* / Q000502:physiology; D013329:Structure-Activity Relationship
D000814:Aniline Compounds; D006219:Halogens; D007462:Iodobenzenes; D018035:Receptors, Odorant; D019817:Benzoic Acid; C031905:iodobenzene; D001554:Benzene; C023650:aniline