The modulatory effects of serotonin and octopamine in the visual system of the honey bee (Apis mellifera L.)

1.	The effects of the biogenic amines serotonin and octopamine on motion-sensitive neurons in the lobula of the honey bee were analysed electrophysiologically. Single cell activity was recorded intracellularly during application of amines. Field potentials in the lobula were recorded to measure the effects on populations of motion-sensitive neurons.
2.	Serotonin and octopamine modulate the response properties of motion-sensitive neurons in the lobula in a functionally antagonistic way.
3.	The application of serotonin, in most cases, reduces background activity as well as responses to moving stripe patterns by motion-sensitive lobula neurons. The direction specificity can also decrease after serotonin application. In accordance with the single cell recordings, the amplitudes of lobula field potentials evoked by moving stripe patterns are also reduced by application of serotonin.
4.	Octopamine leads to an increase in the amplitude and the initial slope of field potentials evoked by moving stripe patterns. However, there were no uniform effects at the single cell level after octopamine application.
5.	The modulatory effects of serotonin and octopamine on motion-sensitive neurons correlate well with some behavioral modifications elicited by these substances (Erber et al. 1991; Erber and Kloppenburg, companion paper).