Octopamine modulates the sensitivity of silkmoth pheromone receptor neurons

Abstract

Effects of octopamine and its antagonist epinastine on electrophysiological responses of receptor neurons of Antheraea polyphemus specialised to the pheromone components (E,Z)-6,11-hexadecadienyl acetate and (E,Z)-6,11-hexadecadienal were investigated. Injections of octopamine and epinastine into the moths had no effect on the transepithelial potential of the antennal-branch preparation nor on the spontaneous nerve impulse frequency in either type of receptor neuron. However, in the presence of continuous low-intensity pheromone stimulation, octopamine significantly increased the nerve impulse frequency in the acetate receptor neuron, but not in the aldehyde receptor neuron. Octopamine and epinastine had no significant effect on the receptor potential amplitudes elicited in both receptor neuron types by pheromone stimulation. However, the peak nerve impulse frequency in the response of both receptor neuron types to pheromone was significantly affected: decreased by epinastine and increased by octopamine over a broad range of pheromone concentrations. In control experiments, injection of physiological saline did not significantly alter the peak nerve impulse frequency. The effect of octopamine was established within 1 h after injection and persisted for about 4 h. The possibility of a direct action of octopamine on the nerve impulse generation by the receptor neurons is discussed.

Identification of the Sex Pheromone of Copitarsia decolora (Lepidoptera: Noctuidae)

“…observed in other species of moths such as A. ipsilon (Gadenne et al 1993), Spodoptera litoralis (Boisduval) (Martel et al 2009) and Mamestra brassica (L.) (Pophof 2000). In these species, this has been attributed to the maturation of the ORNs (Martel et al 2009), changes in hemolymph titers of the juvenile hormone (Gadenne et al 1993;Gadenne & Anton 2000) and neuromodulation of biogenic amines that act on ORNs sensitivity (Pophof 2000;Grosmaitre et al 2001).…”

“…In these species, this has been attributed to the maturation of the ORNs (Martel et al 2009), changes in hemolymph titers of the juvenile hormone (Gadenne et al 1993;Gadenne & Anton 2000) and neuromodulation of biogenic amines that act on ORNs sensitivity (Pophof 2000;Grosmaitre et al 2001). These 3 mechanisms could explain the results observed in C. decolora as well; however studies are needed on these variables for this species.…”

Mating-induced transient inhibition of responses to sex pheromone in a male moth is not mediated by octopamine or serotonin

“…Interestingly, the exogenous administration of both OA and 5-HT increased AL neuron sensitivity of mated males. It was previously shown that OA affects the excitability of ORNs (Grosmaitre et al, 2001;Pophof, 2000;Pophof, 2002). Furthermore, indirect evidence shows that OA can increase the sensitivity of central olfactory neurons in the context of olfactory learning; OA has been shown to stimulate protein kinases A and C, which will in turn regulate the olfactory system by phosphorylating different target proteins (Farooqui, 2007;Müller and Hildebrandt, 1995).…”

“…OA was shown to play a role in the sexual behaviour of male moths by improving pheromone blend discrimination and orientation towards pheromone sources (Linn et al, 1996;Linn and Roelofs, 1986;. It has also been shown to have an effect on ORNs by enhancing the antennal response to pheromone through the modulation of the trans-epithelial potential of olfactory sensilla (Dolzer et al, 2001;Grosmaitre et al, 2001;Pophof, 2000), but not to plant odours (Pophof, 2002). At the central level, OA has been shown to be the responsible transmitter within the reinforcement pathway during associative learning of the honeybee (Farooqui et al, 2003;Hammer, 1993).…”

Neuromodulation in invertebrate sensory systems: from biophysics to behavior

“…In other words, neuromodulation can decrease the threshold stimulus required for generating both action potentials and behavioral responses. For example, in the male silkworm moth (Antheraea polyphemus) octopamine enhances the sensitivity of neurons that detect pheromones (Pophof, 2000). This change in receptor sensitivity correlates with the increased behavioral sensitivity seen in males of several other moth species after octopamine injection (Linn and Roelofs, 1986;Linn et al, 1992Linn et al, , 1996.…”