Glomerular interactions in olfactory processing channels of the antennal lobes

Abstract

An open question in olfactory coding is the extent of interglomerular connectivity: do olfactory glomeruli and their neurons regulate the odorant responses of neurons innervating other glomeruli? In the olfactory system of the moth Manduca sexta, the response properties of different types of antennal olfactory receptor cells are known. Likewise, a subset of antennal lobe glomeruli has been functionally characterized and the olfactory tuning of their innervating neurons identified. This provides a unique opportunity to determine functional interactions between glomeruli of known input, specifically, (1) glomeruli processing plant odors and (2) glomeruli activated by antennal stimulation with pheromone components of conspecific females. Several studies describe reciprocal inhibitory effects between different types of pheromone-responsive projection neurons suggesting lateral inhibitory interactions between pheromone component-selective glomerular neural circuits. Furthermore, antennal lobe projection neurons that respond to host plant volatiles and innervate single, ordinary glomeruli are inhibited during antennal stimulation with the female’s sex pheromone. The studies demonstrate the existence of lateral inhibitory effects in response to behaviorally significant odorant stimuli and irrespective of glomerular location in the antennal lobe. Inhibitory interactions are present within and between olfactory subsystems (pheromonal and non-pheromonal subsystems), potentially to enhance contrast and strengthen odorant discrimination.

How to escape from haller's rule: Olfactory system complexity in small and large Trichogramma evanescens parasitic wasps

“…This suggests that the number of glomeruli is a measure of the diversity of olfactory receptor types, and therefore of the dynamic range of odor molecules that can be perceived. Trichogramma evanescens forms more glomeruli in the antennal lobe than recorded in much larger insects in other orders (e.g., 54 in D. melanogaster flies (Grabe et al, ), 50 in Anopheles gambiae mosquitoes (Ignell et al, ), and 62 in female M. sexta moths (Heinbockel et al, )). Within hymenopteran insects, however, the 100 glomeruli in T. evanescens is the lowest number found so far.…”

10. Moth Sex Pheromone Olfaction: Flux and Flexibility in the Coordinated Confluences of Visual and Olfactory Pathways

“…The majority of AL LNs in moths are inhibitory GABA-ergic (GABA-releasing) neurons and impose lateral inhibition on neighboring glomeruli and on the neurites within individual glomeruli (Hoskins et al 1986;Waldrop et al 1987;Homberg et al 1988Homberg et al , 1990Seki and Kanzaki 2008;Reisenman et al 2011;Heinbockel et al 2013). Combinations of crossglomerular LN synaptic inhibition via their impositions on various combinations of other McGl AL neurons are able to produce PN outputs to protocerebral centers that convey a more precise temporal representation of pheromone odor- note: All scale bars, 100 µm.…”

Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta

“…It is an important model species for investigations of development and metamorphosis (Gilbert et al, 2002; Hiruma and Riddiford, 2010; Nijhout et al, 2014; Truman et al, 2006; Truman and Riddiford, 2007), neurobiology and olfaction (Heinbockel et al, 2013; Martin et al, 2011), lipid metabolism (Canavoso et al, 2001), immunity (Kanost and Nardi, 2010), parasitoid- and pathogen-host interactions (Amaya et al, 2005; Chevignon et al, 2015), mechanisms of Bacillus thuringiensis Cry toxins (Soberon et al, 2010), insect-plant interactions (Schuman et al, 2015), midgut physiology (Wieczorek et al, 2003) and many other aspects of insect biochemistry, physiology, and behavior. Annotation and expression analysis of gene families in the M. sexta genome described here provide new insight into a diversity of important topics in insect biology.…”