ATOMIC-FORCE MICROSCOPY ON THE OLFACTORY DENDRITES OF THE SILKMOTHS ANTHERAEA-POLYPHEMUS AND ANTHERAEA-PERNYI

Olfactory transduction is thought to occur in the outer dendritic memb rane of insect olfactory receptor neurons. Electrophysiological studie s have indicated that the outer dendritic membrane has non-specific ca tion channels and inositol-triphosphate-dependent Ca2+ channels. The p resence of such channels is further supported by the observation that pheromone-stimulated dendrites take up cobalt. However, to date, there is no structural evidence for these channels. Therefore, in order to search for putative ion channels, we have imaged the membrane of the o lfactory dendrites in the scanning electron microscope (SEM) and the a tomic-force microscope (AFM), after extruding the dendrites out of the olfactory hairs and fixing them on plastic coverslips. With the aid o f the SEM, we could see the beaded structure of the dendrite but no fi ne structural details, as the membrane was sputtered with gold. With t he use of the contact mode of the AFM, we could see ''pores'' that wer e deeper than 3 nm and with a diameter of about 15 nm. The density of the ''pores'' was approximately 20/mu m(2) or 10000 pores per thick de ndrite. We believe these to be putative ion channels based on indirect evidence.