The macroglomerular complex of the antennal lobe in the tobacco budworm moth Heliothis virescens: specified subdivision in four compartments according to information about biologically significant compounds

The functional organisation of the male specific macroglomerular complex in Heliothis virescens has been studied by tip recordings of sensilla trichod ea type 1 combined with cobalt-lysine stainings and by intracellular record ings of antennal lobe projection neurons combined with neurobiotin staining s. The antennal lobe, the macroglomerular complex and the stained axons/den drites were reconstructed by carnera-lucida. Some were further computer rec onstructed in three dimensions. The results showed that: 1) The macroglomer ular complex consisted of four anatomically separated compartments; 2) A la rge compartment (the cumulus) at the entrance of the antennal nerve receive d input from receptor neurons responding to the major pheromone component; 3) Another large compartment, located dorso-medially of the cumulus (the do rso-medial compartment) received input from receptor neurons tuned to the s econd pheromone component; 4) Two ventrally located compartments received i nput from two receptor neuron types, co-localized in the same sensillum. Ea ch neuron type responded strongest to one of two interspecifically acting s ignals, shown to interrupt the pheromone attraction. 5) The function of the dorso-medial compartment was further verified by selective arborizations i n this compartment by a projection neuron showing strong response to antenn al stimulation with the second pheromone component. At low concentration, t he neuron responded synergistically to stimulation with the binary pheromon e mixture.