Temporal coding of pheromone pulses and trains in Manduca sexta

Area of Science:

• Neuroscience
• Olfactory receptor function
• Insect behavior

Background:

• Male Manduca sexta moths use olfactory receptors to detect conspecific pheromones for mating.
• Bombykal is the primary component of the male Manduca sexta pheromonal blend.

Purpose of the Study:

• To investigate the temporal response characteristics of pheromone-sensitive olfactory receptors in male Manduca sexta.
• To determine the ability of these receptors to encode pulsed stimuli of bombykal at various frequencies and concentrations.

Main Methods:

• Electrophysiological recordings from olfactory receptor neurons in male Manduca sexta.
• Stimulation with controlled 20-ms pulses of bombykal at varying frequencies (0.5-10 Hz) and concentrations (1, 10, 100 ng).
• Analysis of neuronal response patterns, including adaptation and temporal resolution.

Main Results:

• Isolated bombykal pulses elicited transient receptor activity with a time constant of 160-250 ms.
• Receptors showed temporally modulated responses up to 3 Hz, indicating encoding of pulse trains.
• Short-term adaptation occurred at 10 Hz, and long-term, dose-dependent adaptation was observed.
• Stimulus concentration had minimal impact on temporal resolution.

Conclusions:

• The olfactory receptor population in male Manduca sexta can encode the onset of pheromone pulses at frequencies up to at least 3 Hz.
• Despite individual neuron limitations, the collective receptor response provides temporal information crucial for mate localization.
• These findings contribute to understanding insect olfactory processing and pheromone communication.