Responses of Protocerebral Neurons of the Manduca Sexta to Sex Pheromone Mixtures

Abstract

The olfactory system of the male hawkmoth Manduca sexta is able to discriminate against subtle differences among different mixtures of odorants. Behavioral assays show that this moth is more attracted to the pheromone blend made of two components (E10-Z12-hexadecadienal, or EZ; E10-E12-Z14-hexadecatrienal, or EEZ) in a 2:1 ratio. Alteration of this ratio reduces the attractiveness of the pheromone blend (Lei et al. 2013; Martin et al. 2013). To further test the ratio-selection hypothesis, intracellular recordings from the pheromone-responsive neurons in the delta region of the lateral horn in the protocerebrum of the moth brain—a second-order olfactory center—were conducted and their responses to pheromone blends of different ratios were recorded and examined. However, from the available data we could not draw firm conclusions. This could be a result of many different factors: (1) targeted neuron may be localized outside of the delta region of the protocerebrum; (2) deteriorated condition of brain tissue due to handling; or (3) issues in the delivery of the stimulus protocol. Due to time constraints, the difficulties in staining individual neurons, and the complexity involved in using intracellular recording as a technique to analyze extremely specific neurons, the objectives of this study require further investigation.