Fig. 1. Cell-attached recordings of isolated crypt olfactory receptor neurons (ORNs) and their respective spike-frequency plots (f, s^–1). (A) Amino acids, 8Br-cAMP and IBMX plus forskolin caused a transient increase of the spike frequency in crypt ORNs. Individual cells responded to all three stimuli. In experiments with amino acids or 8Br-cAMP, the excitatory effect reverted to baseline levels within seconds following termination of the stimulus, whereas the combination of IBMX and forskolin induced stronger and longer lasting effects. (B) Temporal response characteristics of silent and tonically active crypt ORNs stimulated with IBMX alone. Higher stimulus concentrations, expressed as the pressure applied to the stimulus pipette by the picospritzer, frequently caused spike suppression during the stimulus followed by prolonged excitation during the post-pulse period. Burst-like activity was observed in a significant proportion of cells (cell 3).