Olfactory protocerebral pathways processing sex pheromone and plant odor information in the male moth Agrotis segetum

We investigated protocerebral processing of behaviorally relevant signals i n the turnip moth, Agrotis segetum. Single neurons were studied both physio logically and morphologically using intracellular recording techniques. In moth pheromone communication systems, the presence of the complete, female- produced pheromone blend is necessary for male attraction. We predicted tha t more protocerebral neurons, compared with AL, would display blend interac tions. However, only a few protocerebral neurons responded differently to t he blend than could be deduced from the response to single components. The majority of the pheromone-sensitive protocerebral neurons identified in thi s study responded to the major pheromone component. In coding time, most AL neurons can follow a 5-Hz odor stimulus, whereas most protocerebral neuron s failed at higher frequencies than 1 Hz. The majority of neurons that resp onded to the odorants tested innervated one or both of the protocerebral la teral accessory lobes. If only one of these was innervated, then the innerv ation always displayed a varicose appearance, suggesting a presynaptic func tion. Thus, information seems to be transferred from other protocerebral. a reas to the lateral accessory lobes. Into these, descending neurons sent sm ooth, postsynaptic branches. A majority of the neurons innervating the supe rior medial protocerebrum were found to display single-component specificit y. Few additional correlations between odor specificity and structural char acteristics were apparent. (C) 2001 Wiley-Liss, Inc.