Abstract
Electrical activities from olfactory cells were recorded extracellularly with a microcapillary electrode which was inserted into the sensillum basiconicum on the antenna of the rice stem borer larvae, Chilo suppressalis WALKER. Each spontaneous spike was diphasic, positive to negative and was not different in shape from that occurring upon chemical stimulation. The sensory cells under stimulation by four kinds of odorous substances, including oryzanone (=p-methyl acetophenon), which is a volatile compound in rice plant being an attractant of the rice stem borer larvae, generally produced a negative slow potential accompanied by an increase in impulse frequency. Dual stimulation by highly concentrated vapours of ether and chloroform elicited different responses : ether evoked the negative slow potential and depressed the spike potential produced by chloroform; while chloroform elicited a positive slow potential and inhibited the spike potential produced by ether. Evidence is discussed which suggests that a succeeding stimulus can modify the electrical response of the receptors of the sensillum to a preceding stimulus.
