ANTENNAL RECEPTIVE-FIELDS OF PHEROMONE-RESPONSIVE PROJECTION NEURONS IN THE ANTENNAL LOBES OF THE MALE SPHINX MOTH MANDUCA-SEXTA

Stimulation of the antenna of the male moth, Manduca sexta, with a key component of the female's sex pheromone and a mimic of the second key component evokes responses in projection neurons in the sexually dimo rphic macroglomerular complex of the antennal lobe. Using intracellula r recording and staining techniques, we studied the antennal receptive fields of 149 such projection neurons. An antennal flagellum was stim ulated in six regions along its proximo-distal axis with one or both o f the pheromone-related compounds while activity was recorded in proje ction neurons. These neurons fell mainly into two groups, based on the ir responses to the two-component blend: neurons with broad receptive fields that were excited when any region of the flagellum was stimulat ed, and neurons selectively excited by stimulation of the proximal reg ion of the flagellum. Projection neurons that were depolarized by stim ulation of one antennal region were not inhibited by stimulation of ot her regions, suggesting absence of antennotopic center-surround organi zation. In most projection neurons, the receptive field was determined by afferent input evoked by only one of the two components. Different receptive-field properties of projection neurons may be related to th e roles of these neurons in sensory control of the various phases of p heromone-modulated behavior of male moths.