Pheromone transduction in moths

Area of Science:

• Insect olfaction
• Neuroethology
• Chemical ecology

Background:

• Male moths locate females at night using species-specific sex pheromones.
• Pheromone filaments are intermittent and encountered at variable concentrations and frequencies during flight.
• Male moth antennae possess olfactory receptor neurons capable of detecting single pheromone molecules.

Purpose of the Study:

• To investigate the signal transduction mechanisms underlying pheromone detection in the hawkmoth Manduca sexta.
• To explore the role of intracellular signaling pathways and hormones in olfactory processing.
• To propose a new hypothesis for temporal odor encoding in insect olfactory systems.

Main Methods:

• Analysis of metabotropic PLCβ-dependent signal transduction cascades for pheromone detection.
• Investigation of receptor-guanylyl cyclases for adaptation to strong or prolonged stimuli.
• Examination of hormonal modulation (e.g., octopamine) on sensory neuron second messenger levels.

Main Results:

• Brief pheromone stimuli activate a PLCβ-dependent cascade leading to transient Ca(2+) changes.
• Strong stimuli activate receptor-guanylyl cyclases, inducing long-term adaptation.
• Octopamine enhances temporal resolution in sensory neurons during the activity phase.

Conclusions:

• Odor detection involves synergistic gating of ion channels by intracellular Ca(2+) and cyclic nucleotide levels.
• A novel hypothesis proposes cyclic nucleotide-dependent ion channels control subthreshold oscillations for temporal odor encoding.