Characterization of octopaminergic descending unpaired median neurons in the suboesophageal ganglion in Manduca sexta
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1
Institut für Biologie-Neurobiologie, FU Berlin, Germany
Octopamine is a major biogenic amine in the insect nervous system where it functions as a neuromodulator acting on glands, sense organs or muscles, as a neurohormone mobilizing carbohydrates or lipids or as a neurotransmitter. It is considered to play an important role in initiation and maintenance of motor programs.
In the insect nervous system two main populations of octopaminergic neurons exist: paired neurons and unpaired median (UM) neurons. Paired neurons occur in the brain and some segmental ganglia. In contrast, UM neurons can be found in all segmental ganglia but not in the brain. These neurons exhibit dorsally or ventrally located cell bodies with bilaterally symmetrical axons.
The segmental ganglia contain efferent UM neurons projecting into peripheral nerves and innervating peripheral targets like glands, muscles or sense organs. In contrast, the suboesophageal ganglion (SOG), a higher center for motor coordination, possesses two main populations of intersegmental UM neurons: ascending UM neurons innervating principal brain neuropils and descending UM neurons projecting towards the thoracic ganglia. Electrophysiological and neuroanatomical evidence suggest that at least some of them descend to the terminal ganglion with broad aborizations in each segmental ganglion.
To characterize descending UM neurons of the SOG with respect to their sensory input and morphology we performed intracellular recordings and staining in combination with electrical stimulation of peripheral nerves of either the thoracic ganglia or the SOG, i.e. of the mouthparts, in the larval tobacco hawkmoth Manduca sexta. Stimulation of thoracic nerve 2a containing axons of several proprioreceptors of the larval leg e.g. the femoral and tibial chordotonal organ and hair sensilla evoked excitatory or inhibitory responses of the three larval descending UM neurons. This indicates a differential sensory input of these neurons. Furthermore, our results reveal inhibitory input from the mandibular, labial and maxillar nerve and thoracic nerve 1a containing axons of dorsal thoracic hairlike sensilla.
Additionally, preliminary results of simultaneous intracellular recordings of descending UM neurons of the SOG and motor neurons of the thoracic ganglia suggest a possible connection.
Keywords:
Biogenic Amines,
Insects,
Neuromodulation,
Octopamine
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster Presentation (see alternatives below as well)
Topic:
Neuromodulation
Citation:
Erdmann
J
(2012). Characterization of octopaminergic descending unpaired median neurons in the suboesophageal ganglion in Manduca sexta.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00081
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Received:
02 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Ms. Jessika Erdmann, Institut für Biologie-Neurobiologie, FU Berlin, Berlin, Germany, jerdmann@live.de