Pheromone processing center in the protocerebrum of Bombyx mori revealed by nitric oxide‐induced anti‐cGMP immunocytochemistry

Abstract

The antennal lobe (AL) of the male silkworm moth Bombyx mori contains 60 +/- 2 ventrally located antennal glomeruli and a dorsal macroglomerular complex (MGC) consisting of three subdivisions. The response patterns of MGC projection neurons (PNs) to pheromonal stimuli correlate with their dendritic arborization in the subdivisions of the MGC. However, the representation of this pheromonal information in the lateral protocerebrum (LPC), which is the target site of the AL PNs, is not well known. We performed nitric oxide (NO)-induced anti-cGMP immunohistochemistry and found that the PNs which respond to the major pheromone component (bombykol) express strong immunoreactivity. They project to a specific area, the delta area in the inferior lateral protocerebrum (DeltaILPC), which clearly represents the processing center for the major pheromone component. Furthermore, to examine the projection sites in the LPC from each subdivision of the MGC, we performed double-labeling of each type of MGC-PNs, combined with NO-induced anti-cGMP immunohistochemistry. We revealed that projections from each subdivision of the MGC overlapped or separated in specific regions of the DeltaILPC. These results suggest that integration and segregation of pheromone information may occur in the DeltaILPC.

Spatial representation of alarm pheromone information in a secondary olfactory centre in the ant brain

“…We found no region to specifically represent alarm pheromone information: terminal boutons of pheromone-sensitive PNs were widely distributed in the l ho and all regions that received alarm pheromone information also received non-pheromonal information. This is in contrast to the findings in some species of insects that the area to represent sex pheromone information is in large part segregated from the area to represent information on other odours in the l ho (cockroaches: Nishino et al 2003;moths: Kanzaki et al 2003;Seki et al 2005; fruit-flies: Jefferis et al 2007). However, we found an area in the antero-medial region of the l ho in which terminal boutons of pheromone-sensitive PNs are significantly more densely distributed than in the rest of the l ho but those of pheromone-insensitive PNs are not.…”

Tonic and stimulus-evoked nitric oxide production in the mouse olfactory bulb

“…An extensive literature documents the intense expression of the NOS enzyme in olfactory centers of diverse species of vertebrates (Bredt et al, 1991;Kishimoto et al, 1993;Spessert et al, 1994;Dellacorte et al, 1995;Hopkins et al, 1996;Alonso et al, 1998;Crespo et al, 2003;Gutierrez-Mecinas et al, 2005;Herrmann et al, 2007) and invertebrates (Gelperin, 1994;Elphrick et al, 1995;Muller and Hildebrandt, 1995;Nighorn et al, 1998;Fujie et al, 2002;Seki et al, 2005;Settembrini et al, 2007;Watanabe et al, 2007). However, odorantevoked NO production was only recently demonstrated in the moth antennal lobe using a fluorescent indicator (Collmann et al, 2004).…”

Olfaction in vector-host interactions

“…They further propose that the LH is globally organised according to biological values rather than chemical nature of the odorant information. This finding is reminiscent of the male silkworm moth, Bombyx mori, where PNs from the macroglomerular complex representing sex pheromones send axon projections to a discrete area in the lateral protocerebrum (Seki et al 2005). Spatial segregation of the pheromone representation in higher olfactory centres may therefore be a conserved feature in insects.…”