Sensory processing of environmental- CO2 information in the moth nervous system

GUERENSTEIN PG; CHRISTENSEN TA; HILDEBRAND JG

Florida

Congreso; Twenty-fourth Annual Meeting of the Association for Chemoreception Sciences; 2002

Association for Chemoreception Sciences

Insects can sense the CO2 level in the air around them, and they are thought to use that information in vital tasks such as locating food sources. It is uncertain, however, how that information is processed by the CNS. In order to address this issue, we are studying the highly developed CO2-sensing system of the moth Manduca sexta. We have characterized the physiology of CO2-receptor cells located in the labial palps by means of extracellular recordings, and of CO2-responding neurons in the CNS using intracellular techniques. In addition, we have used staining techniques to study the central projections of CO2-receptor cells and the arborization pattern and projections of CNS neurons that respond to CO2. Our results suggest that (1) the receptor cells in the labial palps of female Manduca are specialized for the measurement of the surrounding CO2 level; (2) those cells can encode step increases and decreases in CO2 concentration, as well as the background CO2 level; (3) their axons project bilaterally to a specific glomerulus in the antennal AChemS Abstracts A87lobe (AL) of the brain, confirming previous findings; (4) neurons in the AL receive and process CO2 information from the labial palps, confirming that the AL is the primary site for processing CO2 information; and (5) CO2-responding AL neurons can encode increases in CO2, but their ability to encode decreases in CO2 appears to be limited. Our findings reinforce the idea that information about environmental CO2 plays important roles in the biology of moths and motivate further investigations of this remarkable chemosensory subsystem.