Figure 3.

Odor responses of excitatory local neurons increase after chronic removal of some olfactory receptor neurons. A, We recorded responses from eLNs while stimulating the palps with odors. Antennae were removed either acutely or chronically. B, Responses of two typical eLNs to the same odor. One was recorded after acute antennal removal, the other after chronic removal. Note large spontaneous IPSPs (arrowhead), which are typical of eLNs. Rasters (below) show spiking activity in the same cells in five consecutive trials. Odor is ethyl acetate, 500 ms pulse. C, Average odor-evoked firing rates in eLNs in response to four odors (described in Fig. 1). Firing rate was averaged over a 500 ms window starting 100 ms after nominal odor onset. Firing rates are significantly higher after chronic versus acute antennal removal (p < 0.05, two-way ANOVA, n = 7 acute and 6 chronic). D, There is no significant difference in the resting potential of eLNs (p > 0.05, t test, n = 7 and 6 for acute and chronic, respectively). E, There is no significant change in eLN excitability. Membrane potential changes were elicited by injecting current into the eLN soma, and firing rates were measured for each level of depolarization. The relationship between membrane potential and firing rate is not significantly different (p > 0.05 for all bins, t test, n = 7 acute and 6 chronic). Additionally, the bar graph (right) shows that the slope of a line fitted individually for each cell within the linear range (−42.5 to −7.5 mV) is not significantly different between acute and chronic removal (p > 0.05, Mann–Whitney U test).