Fig. 5. Cross-adaptation experiments suggest the presence of relatively independent receptor sites for each of the polyamine odorants tested. The electro-olfactogram (EOG) responses to each test odorant in (A) putrescine (Put), (B) cadaverine (Cad), (C) histamine (His), (D) spermidine (Spd), (E) spermine (Spm), (F) agmatine (AGB) and (G) L-glutamine (Gln) competitor odorant backgrounds are expressed as a percentage of the response obtained to the odorant prior to switching into the competitor odorant background. Each competitor odorant was tested on three fish. The dotted line indicates the level of response predicted if no cross-adaptation is occurring. Asterisks designate responses significantly greater than the self-adapted response to the background odorant (one-way ANOVA, Dunnett's post hoc t-test; P<0.05). Values are means ± S.E.M.