Figure 3.

SO–OSNs respond to homologous compounds with the same functional group. We tested the responses of 26 SO neurons to acids or aldehydes with different carbon chain length (C4 to C9). Most of the responsive neurons (19 of 26; 73%) responded to all acids or aldehydes at concentrations of 1 or 100 μm. A, A single neuron responded to aliphatic acids (all at 100 μm). B, Another neuron responded to aliphatic aldehydes (all at 100 μm). The holding potential was −65 mV for both neurons. The gray trace (Ringer) in each cell was the mechanical response induced by a Ringer puff that was delivered with the same pressure as the odorant puffs.