SUGAR RESPONSE DIFFERENCES RELATED TO SENSILLUM TYPE AND LOCATION ON THE LABELLA OF PROTOPHORMIA-TERRAENOVAE - A CONTRIBUTION TO SPATIAL REPRESENTATION OF THE STIMULUS

The chemoreceptor spike activity in response to sucrose in the concent ration range 1-500 mM was recorded from each of the 11 Intermediate an d 13 Large labellar sensilla in the blowfly Protophormia terraenovae. The results showed that: (1) three of the four cells present in each s ensillum are activated by sucrose stimulation: (2) differences between the Large and Intermediate types exist in the dose-response profiles of one of these cells (the 'water' cell), possibly reflecting differen t sugar receptor site populations on the dendritic membranes of homolo gous cells in the two types, (3) sensilla of both types are differenti ally responsive to sucrose solutions according to their location on th e labellum. These differences may provide elements for a spatial repre sentation of the stimulus source within the sensory coding process. (C ) 1998 Elsevier Science Ltd. All rights reserved.