Chemical Senses Advance Access originally published online on March 20, 2009
Chemical Senses 2009 34(5):363-372; doi:10.1093/chemse/bjp013
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© 2009 The Authors
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Morphological and Physiological Characteristics of the Serotonin-Immunoreactive Neuron in the Antennal Lobe of the Male Oriental Tobacco Budworm, Helicoverpa assulta
Department of Psychology/Neuroscience Unit, MTFS, Norwegian University of Science and Technology (NTNU), 7489 Trondheim, Norway
Correspondence to be sent to: Bente Gunnveig Berg, Department of Psychology/Neuroscience Unit, MTFS, Norwegian University of Science and Technology (NTNU), 7489 Trondheim, Norway. e-mail: bente.berg{at}ntnu.no
| Abstract |
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We have characterized, by intracellular recording and staining combined with immunocytochemistry, a serotonin-immunoreactive neuron in the central olfactory pathway of the male moth Helicoverpa assulta. The neuron joins the unique category of so-called SI antennal-lobe neurons, previously described in several insect species. In similarity with that originally discovered in the sphinx moth Manduca sexta, the neuron identified here has a large soma located posteriorly in the lateral cell cluster of the antennal lobe and an unbranched neurite projecting into the ipsilateral protocerebrum via the inner antennocerebral tract. After bypassing the central body, the axon crosses the midline and extends through the corresponding antennocerebral tract to the contralateral antennal lobe where it innervates the entire assembly of glomeruli including the male-specific macroglomerular complex. The neuron arborizes into several fine branches in bilateral protocerebral regions anterior to the calyces of the mushroom bodies, particularly on the contralateral side. The physiology of the neuron revealed 2 distinctly different spiking amplitudes, 1 small showing a relatively high spontaneous activity and 1 large showing low activity. The small-amplitude spikes displayed increased frequency when pheromones and plant odors were blown over the antenna. The large-amplitude spikes, which had an unusually long duration, showed no observable responses.
Key words: biogenic amine, centrifugal neuron, heliothine moth, 5-hydroxytryptamine, olfactory system, two spiking amplitudes
This work was supported by the Norwegian Research Council (project no. 1141434).
Accepted 19 February 2009