Physiology and morphology of projection neurons in the antennal lobe of the male mothManduca sexta

Abstract

1. We have used intracellular recording and staining, followed by reconstruction from serial sections, to characterize the responses and structure of projection neurons (PNs) that link the antennal lobe (AL) to other regions of the brain of the male sphinx moth Manduca sexta. 2. Dendritic arborizations of the AL PNs were usually restricted either to ordinary glomeruli or to the male-specific macroglomerular complex (MGC) within the AL neuropil. Dendritic fields in the MGC appeared to belong to distinct partitions within the MGC. PNs innervating the ordinary glomeruli had arborizations in a single glomerulus (uniglomerular) or in more than one ordinary glomerulus of one AL (multiglomerular) or in one case, in single glomeruli in both ALs (bilateral-uniglomerular). One PN innervated the MGC and many or all ordinary glomeruli of the AL. 3. PNs with dendritic arborizations in the ordinary glomeruli and PNs associated with the MGC typically projected both to the calyces of the ipsilateral mushroom body and to the lateral protocerebrum, but some differences in the patterns of termination in those regions have been noted for the two classes of PNs. One PN conspicuously lacked branches in the calyces but did project to the lateral protocerebrum. The PN innervating the MGC and many ordinary glomeruli projected to the calyces of the ipsilateral mushroom body and the superior protocerebrum. 4. Crude sex-pheromone extracts excited all neurons with arborizations in the MGC, although some were inhibited by other odors. One P(MGC) was excited by crude sex-pheromone extract and by a mimic of one component of the pheromone blend but was inhibited by another component of the blend. 5. PNs with dendritic arborizations in ordinary glomeruli were excited or inhibited by certain non-pheromonal odors. Some of these PNs also responded to mechanosensory stimulation of the antennae. 6. The PN with dendritic arborizations in the MGC and many ordinary glomeruli was excited by crude sex-pheromone extracts and non-pheromonal odors and also responded to mechanosensory stimulation of the antenna.

Calcium Current Diversity in Physiologically Different Local Interneuron Types of the Antennal Lobe

“…In parallel, we will present, as a reference, data from uniglomerular projection neurons (uPNs). Projection neurons generate Na ϩ -driven action potentials, and their morphology and response properties are well known in the cockroach (Burrows et al, 1982;Ernst and Boeckh, 1983;Boeckh and Ernst, 1987;Malun et al, 1993;Distler and Boeckh, 1997a) and other insects [Apis mellifera (Sun et al, 1997;Abel et al, 2001), Drosophila melanogaster (Wilson et al, 2004), Schistocerca americana (Wehr and Laurent, 1996;Stopfer and Laurent, 1999;Stopfer et al, 2003;Bazhenov et al, 2005;Broome et al, 2006), and different moths (Waldrop et al, 1987;Kanzaki et al, 1989;Hansson et al, 1994;Masante-Roca et al, 2005;Namiki et al, 2008)]. In the second part, we present a detailed analysis of the voltage-activated Ca 2ϩ currents in two physiologically different LN types and uPNs.…”

The anatomical pathways for antennal sensory information in the central nervous system of the cricket, Gryllus bimaculatus

“…Almost all of the AL-PNs that project through IACT show uniglomerular arborization in the AL (Schildberger, 1984;Ignell et al, 2001) as they do in other insects (cockroach: Malun et al, 1993;Strausfeld and Li, 1999;honeybee: Abel et al, 2001;Müller et al, 2002;moth: Homberg et al, 1989;Kanzaki et al, 1989;fly: Stocker et al, 1990;Marin et 27 al., 2002;mosquito: Ignell et al, 2005). In the cockroach, AL-PNs project via ACT2 and there they also exhibit uniglomerular arborization (Malun et al, 1993).…”

“…For example, male insects have sex specific glomeruli, the macroglomerular complex, which exclusively process information regarding sex pheromones released by conspecific females (cockroach: Burrows et al, 1982;moth: Christensen and Hildebrand, 1987;Kanzaki et al, 1989; fly: Kondoh, 2003;Stockinger et al, 2005). Further, in the moth, female specific glomeruli process odor information concerning host plants ( Masante-Roca et al, 2005;Skiri et al, 2005).…”

Humanitarian Demining Using an Insect Based Chemical Unmanned Aerial Vehicle

“…Our neural based model relies on two important hypotheses, the use of stereo information and the pheromone frequency dependency. The first hypothesis is supported by the, so called, flip/flop neurons (Kanzaki et al 1989). These are, so called, Descending Neurons of the protocerebrum that arborize in the Lateral Accessory Lobe, and that show a bi-stable high and low frequency response.…”

“…The second corner stone of the model is based on the Macro Glomerular Complex (MGC) of the Antennal Lobe (AL) of the moth, a glomerulus that evolved to solely process the pheromone signals (Christensen & Hildebrand 1987;Kanzaki et al 1989;Hansson et al 1991;Christensen et al 1993;Christensen et al 1995). Approximately 85% of the neurons of the MGC display transient responses correlated with the pheromone signal, but are only able to resolve odor pulses of up to a few Hz (Christensen & Hildebrand 1987;Christensen et al 1993;Lei & Hansson 1999).…”