Date of Award

1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

John T. Caprio

Abstract

Both electro-olfactogram and integrated multiunit receptor responses of populations of olfactory receptor neurons (ORNs) clearly showed that responses to complex mixtures were predictable. Results demonstrated that receptor sites for basic and acidic amino acids, respectively, are independent from those for neutral amino acids and multiple receptor site types with highly overlapping specificities exist for amino acids within each group. Results also confirmed that one mechanism for synergism is the simultaneous activation of relatively independent receptor sites by the components in a mixture, and there was no evidence of mixture suppression. Single ORNs recorded in vivo responded to stimuli with either excitation, suppression or both. Results suggested that suppressive responses, as well as excitatory responses, play important roles in olfactory coding. The result that 55% of the single ORNs studied responded to more than one stimulus suggested that multiple receptor site types for different odorants were expressed in the plasma membranes of single ORNs. Responses of single ORNs to binary mixtures of amino acids indicated that although mixture interactions occurred, none changed response types from those observed to the individual components. Thus, the observed response types to the tested component-similar binary mixtures were predictable. Responses of single olfactory bulb neurons to amino acids were highly reproducible over time. Results suggested that suppressive as well as excitatory responses are involved in both quality and quantity coding of olfactory information. Response types of olfactory bulb neurons to a given stimulus at different concentrations did not change from excitation to suppression, or vice versa. The responses of single olfactory bulb neurons to binary mixtures were highly associated with the responses to the components. Although mixture interactions occurred, mixture interactions that changed olfactory bulb neuron response types from those observed to the individual components were rare. The results indicated that responses to binary mixtures whose components evoked the same response types were generally predictable, whereas predictability of responses to the component-different binary mixtures was dependent upon the specific types of mixtures tested.

Pages

208

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