Spatial distribution of receptor-responses to stimulation with different odours.

The olfactory receptor-responses recorded from the enzinentia olfactoria in the frog were studied to find whether receptors with different specificities were homogeneously or non-homogeneously distributed. Receptor potentials (EOGs) were recorded simultaneously from two different areas of the eminentia olfuctoria. 21 different substances were used; 8 of these substances belonged to a homologous serie of cycloketones. For each substance the ratio N between the two EOG-amplitudes was measured. N-values obtained with the recording electrodes kept at fixed positions were found to vary for different odours and for different concentrations of the same odour. By recording with one electrode at different distances from the other fixed electrode N-values for different areas were obtained for each odour. The N-values showed an increase for some odours and a decrease for others. These observations indicate a non-homogeneous distribution of receptors with different specificities. For the cycloketones, at the concentrations used, only small variations were found in N-values at all positions tested. Keeping one electrode fixed and placing the other stepwise away in a posterior or lateral direction, a successive general reduction in N-values for all the substances was found. This suggests a general reduction in receptor density in posterior and lateral direction. I would like to thank Dr. Kjell Doving for suggesting the topic, and for his constant en couragement during the work. The cycloketones were kindly provided by International Flavor & Flagrances, Holland.