Figure 6.
Abolishing olfactory receptor neuron spikes is insufficient to induce plasticity. A, To find an odor stimulus that activates solely Or83b-independent ORNs, we recorded field potentials from the antenna in both control flies and Or83b mutants. B, Average antennal field potential responses to the odor 1,4-diaminobutane (DAB) (at 10−5 dilution). These responses are not different in controls versus Or83b mutants. Because the antennal field potential is a good proxy for total ORN activity (Olsen et al., 2010), this result indicates that ORN responses to this stimulus are largely independent of Or83b. As a control, we verified that the response to a second odor, pentyl acetate (PEN), is substantially diminished in Or83b mutants, as expected from the fact that this stimulus drives activity in many Or83b-dependent ORNs (Hallem and Carlson, 2006). C, We recorded from PNs in the palp glomerulus VM7 while stimulating the antenna with DAB (10−5 dilution). Because spikes in VM7 ORNs are completely abolished by the Or83b mutation (Olsen et al., 2007), this experiment tests whether excitatory local neuron input to PNs is affected when spikes to that PN are eliminated. Palps were removed acutely to minimize spontaneous activity in the PN. D, Representative recordings show that the response to DAB (10−5 dilution) is similar in control and mutant VM7 PNs. Similar results were observed in multiple recordings (n = 4 control and 2 mutant).