Hyperpolarizing receptor potentials in lobster olfactory receptor cells: Implications for transduction and mixture suppression

Physiological studies of olfactory receptor cells have focused on excitatory responses, in part because the evidence for inhibitory responses from extracellular recordings, although long-standing, has been equivocal. Intracellular recording from the olfactory cells of two species of lobsters revealed that small but concentrationdependent and repeatable hyperpolarizing receptor potentials could be evoked by a mixture of L-arginine, L-cysteine and L-proline, as well as by histamine. Large, depolarizing receptor potentials were evoked in the same cells by a complex odor mixture. Simultaneous application of depolarizing and hyperpolarizing stimuli reduced the magnitude of the evoked depolarization. These results imply that multiple, opposing transduction mechanisms are present in single lobster olfactory receptor cells and reveal a noncompetitive mechanism for peripheral mixture suppression.