RESPONSE PROPERTIES OF STAINED MONOPOLAR CELLS IN THE HONEYBEE LAMINA

1. Monopolar cells of the first visual ganglion, the lamina, of the be e were recorded from and stained intracellularly. 2. Several different response types to pulses of spectral light were found. The most commo n response type hyperpolarized in a phasic-tonic fashion. The tonic hy perpolarizing response frequently decreased gradually, but in some cas es increased with lasting illumination. Some cells also gave a transie nt response to light-OFF. In contrast, one stained and several unstain ed cells showed depolarizing responses. Five cells exhibited spiking r esponses under normal physiological conditions. 3. The V/log I-functio ns were steeper than those of the photoreceptors and, in some cases, h ad both rising and failing parts with increasing intensities. The spec tral sensitivity obtained with the constant response method showed a p eak in the green (510-535 nm) in most cells. A series of spectral flas hes revealed an additional type with highest sensitivity in UV. Indire ct evidence was found in one cell for spectral opponent processing. 4. Two morphological types of monopolar cells were stained. These corres pond well to Ribi's (1976) L1 and L2 cells, with some differences in d etail. The most frequently stained cell type closely resembles his L2 type. All 3 stained spiking cells were of this type.