Modulation by Octopamine of Olfactory Responses to Nonpheromone Odorants in the Cockroach, Periplaneta americana L.

Abstract

Olfactory receptor cells in insects are modulated by neurohormones. Recordings from cockroach olfactory sensilla showed that a subset of sensory neurons increase their responses to selected nonpheromone odorants after octopamine application. With octopamine application, recordings demonstrated increased firing rates by the short but not the long alcohol-sensitive sensilla to the nonpheromone volatile, hexan-1-ol. Within the same sensillum, individual receptor cells are shown to be modulated independently from each other, indicating that the octopamine receptors reside in the receptor not in the accessory cells. A uniform decrease in the amplitude of electroantennogram, which is odorant independent, is suggested to reflect the rise in octopamine concentration in the antennal hemolymph. Perception of general odorants measured as behavioral responses changed qualitatively under octopamine treatment: namely, repulsive hexan-1-ol became neutral, whereas neutral eucalyptol became attractive. Octopamine induced a change in male behavioral responses to general odors that were essentially the same as in the state of sexual arousal. Our findings suggest that sensitivity to odors having different biological significances is modulated selectively at the peripheral as well as other levels of olfactory processing.

Grooming Behavior in American Cockroach is Affected by Novelty and Odor

“…Grooming as nonspecific mechanism of signal cleanup is probably a widespread phenomenon; it was noticed in different insect species challenged with pheromone and nonpheromone odors [39–41]. Our present data shows that eucalyptol, the general odorant which causes excitation of a receptor cell housed in male-specific pheromone-sensitive antennal sensilla [30, 42] induces significant changes in the frequency of antennal grooming.…”

“…The setup consisted of 3 components: a transparent plastic cage (30 × 45 × 30 cm) containing food and water, a shelter (17.0 × 17.0 × 5.5 cm) that was constantly dark inside, and an exchangeable test chamber (20 × 20 × 8 cm); the latter 2 were separated from the cage with plastic doors (modified from [30]). At the beginning of testing, the door between the shelter and the cage was shut, and the door between the cage and test chamber was open for a short time, allowing only one insect to enter in it.…”

“…It was noticed that restrained antenna is becoming wetted after a course of odor stimulation and was suggested that liquid exudation is likely functioning in removing residual ligands [30]. Since the liquid is removed by grooming [26], the purpose of current study was to describe in detail the frequency and timing of this particular behavior with special emphasis on novelty and odor traits.…”

Trace amines inhibit insect odorant receptor function through antagonism of the co-receptor subunit

“…Melatonin also appears to exert neuromodulatory effects in insects 54, 55 . Interestingly, many of these amines modulate the olfactory system 56– 58 .…”

Insects groom their antennae to enhance olfactory acuity

“…We observed that antennae of the American cockroach, Periplaneta americana (Linnaeus) (Blattodea, Blattidae), that were immobilized for electrophysiological studies, accumulated a shiny substance on their surface (18). We hypothesized that grooming might serve to remove these excess native secretions and compared groomed and nongroomed antennae of male P. americana cockroaches using field emission gun scanning electron microscopy (FEG SEM).…”