An Examination of the Effects and Possible Targets of Nitric Oxide on Olfactory Neurons in the Moth, Manduca Sexta

Persistent Link:
http://hdl.handle.net/10150/195172
Title:
An Examination of the Effects and Possible Targets of Nitric Oxide on Olfactory Neurons in the Moth, Manduca Sexta
Author:
Wilson, Caroline Hamilton
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The gaseous messenger, nitric oxide (NO), has emerged as a key component of olfactory systems. Localization and imaging studies in the moth, Manduca sexta, suggest that NO may affect the excitability of olfactory neurons by modifying neuronal membrane properties through sGC-dependent mechanisms. This hypothesis was tested using a multidisciplinary approach, including two types of physiological recording techniques and immunocytochemical analysis of sGC antibody expression in the Manduca brain. The excitability of large populations or individual antennal lobe (AL) neurons was monitored with in vivo physiological recordings while various NO pharmacological agents were bath applied to the brain. To examine possible targets of NO, the binding site of sGC was blocked and the results were compared to NO blockade. Finally, sGC immunocytochemistry was used to also determine possible targets of NO.Two NO synthesis inhibitors and a sGC blocker were potent effectors of resting, baseline activity in the Manduca brain. Blocking NO synthesis caused significant decreases in AL neuron conductance. This conductance decrease led to changes in baseline activity, including the appearance of bursts in some neurons, and increased and decreased firing rates in other neurons. Further, the neurons had a decreased responsiveness and excitability to presynaptic input. Blocking the sGC binding site caused similar effects in most neurons, which indicates that NO likely acts through sGC-dependent signaling to exert its effects in at least a subset of neurons. However, some neurons had different responses to NO and sGC blockade, which indicates that NO may act through other signaling mechanisms in some neurons. Further examination using sGC immunocytochemistry revealed that only about 90% of projection neurons (PNs) and 30% of local neurons (LNs) contained sGC immunoreactivity.The results in this dissertation indicate that NO performs a global function in the antennal lobe to maintain the resting membrane conductance of AL neurons. NO likely exerts its effects through both sGC-dependent and sGC-independent mechanisms. Finally, these results have major implications for odor coding in all species, as NO has been found in the olfactory systems of every animal examined thus far.
Type:
text; Electronic Dissertation
Keywords:
olfaction; Manduca sexta; moth; nitric oxide; gaseous neurotransmitters
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Neuroscience; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Nighorn, Alan J

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleAn Examination of the Effects and Possible Targets of Nitric Oxide on Olfactory Neurons in the Moth, Manduca Sextaen_US
dc.creatorWilson, Caroline Hamiltonen_US
dc.contributor.authorWilson, Caroline Hamiltonen_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe gaseous messenger, nitric oxide (NO), has emerged as a key component of olfactory systems. Localization and imaging studies in the moth, Manduca sexta, suggest that NO may affect the excitability of olfactory neurons by modifying neuronal membrane properties through sGC-dependent mechanisms. This hypothesis was tested using a multidisciplinary approach, including two types of physiological recording techniques and immunocytochemical analysis of sGC antibody expression in the Manduca brain. The excitability of large populations or individual antennal lobe (AL) neurons was monitored with in vivo physiological recordings while various NO pharmacological agents were bath applied to the brain. To examine possible targets of NO, the binding site of sGC was blocked and the results were compared to NO blockade. Finally, sGC immunocytochemistry was used to also determine possible targets of NO.Two NO synthesis inhibitors and a sGC blocker were potent effectors of resting, baseline activity in the Manduca brain. Blocking NO synthesis caused significant decreases in AL neuron conductance. This conductance decrease led to changes in baseline activity, including the appearance of bursts in some neurons, and increased and decreased firing rates in other neurons. Further, the neurons had a decreased responsiveness and excitability to presynaptic input. Blocking the sGC binding site caused similar effects in most neurons, which indicates that NO likely acts through sGC-dependent signaling to exert its effects in at least a subset of neurons. However, some neurons had different responses to NO and sGC blockade, which indicates that NO may act through other signaling mechanisms in some neurons. Further examination using sGC immunocytochemistry revealed that only about 90% of projection neurons (PNs) and 30% of local neurons (LNs) contained sGC immunoreactivity.The results in this dissertation indicate that NO performs a global function in the antennal lobe to maintain the resting membrane conductance of AL neurons. NO likely exerts its effects through both sGC-dependent and sGC-independent mechanisms. Finally, these results have major implications for odor coding in all species, as NO has been found in the olfactory systems of every animal examined thus far.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectolfactionen_US
dc.subjectManduca sextaen_US
dc.subjectmothen_US
dc.subjectnitric oxideen_US
dc.subjectgaseous neurotransmittersen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineNeuroscienceen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorNighorn, Alan Jen_US
dc.identifier.proquest1431en_US
dc.identifier.oclc137355780en_US
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