Mary Teresa Lucero, Ph.D. - US grants

DESCRIPTION (Adapted from the Investigator's Abstract):The current theory of how the olfactory system distinguishes between odorant mixtures is based on the idea that the patterning of activity across many sensory neurons in the olfactory epithelium is integrated and recognized by higher centers in the brain. Odorant binding to membrane receptors on the cilia of olfactory receptor neurons activates one of several transduction pathways leading to depolarizing or hyperpolarizing responses that change the tonic firing rate of the olfactory receptor neurons. The discovery of multiple transduction pathways in a single olfactory receptor neuron suggests these cells are capable of integrating multiple inputs. Surprisingly, the biophysical and biochemical bases of olfactory mixture interactions have not been systematically investigated using both electrophysiological and fluorescent imaging methods. This proposal focuses on the mechanisms by which odorant mixtures activate different transduction pathways and thereby affect the integrated output of olfactory receptor neurons. The first specific aim is directed toward a characterization of the biophysical properties of the transduction pathways. This involves determination of concentration-response functions, conductance changes, and the ionic basis of transduction in squid olfactory neurons. The physiologically relevant odorants: dopamine, proline, AMP, and ADP will be used. Dopamine is an alarm substance found in squid ink that elicits strong aversive behavior in squid and hyperpolarizes olfactory receptor cells. Proline, AMP, and ADP stimulate appetitive behavior and depolarizing receptor potentials. The second specific aim will be the identification of the signal transduction mechanisms for each odorant. The third specific aim will be the effects of mixtures of odorants on activating multiple transduction pathways in a single receptor neuron. If mixture responses deviate from responses predicted on biophysical grounds, biochemical level interactions will be implicated and investigated.This work will provide insights into receptor level coding of odorant mixtures.

Olfactory receptor neurons (ORNs) have been assigned the incredible task of distinguishing between over 10,000 odor molecules. Not only must ORNs decipher the quality of odors, they must also provide the brain with intensity information. Recent studies have made considerable progress in identifying and characterizing the components of signal transduction machinery in ORNs. Odors binding to receptor proteins on olfactory cilia initiate a G-protein-mediated second messenger cascade that results in the transient elevation of cAMP or IP3. Both second messengers gate specific ion channels in the ciliary membrane, resulting in the generation of receptor potentials. Olfactory mucus provides the perireceptor environment in which the initial steps of the transduction of a chemical odor signal to an electrical receptor potential occur. Extrinsic autonomic and trigeminal innervation controls mucus secretion and may release neurotransmitters into the mucus. The presence of antioxidant chemicals in the mucus suggests that the mucus environment is permissive for neurotransmitter persistence yet the actions of those neurotransmitters are unclear. The sensitivity of ORNs to cAMP-generating odors is determined by both the sensitivity of the receptor proteins and the sensitivity of the cyclic nucleotide gated (CNG) channel. One possible role for neurotransmitters released into olfactory mucus is to modulate ORNs odor sensitivity. Potential sites for modulation include the receptor proteins, transduction cascades, and effector channels. The work in this proposal will test the hypotheses that the neurotransmitter dopamine is present in olfactory mucus, acts on D2 dopamine receptors on ORN dendrites and modulates the sensitivity of the system by changing basal levels of cAMP production. Our model suggest that the presence of dopamine in the mucus is under autonomic control and that increases or decreases in dopamine would increase or decrease the sensitivity of ORNs. This model fits with observations that stimulation of the trigeminal system decreases odor sensitivity in frogs, and that the psychophysical perception of odor intensity decreases after exposure to noxious substances (trigeminal stimuli). These studies may be clinically relevant to diseases where dopaminergic pathways are disturbed (Parkinson's) and which display decreased olfactory sensitivity as an early symptom. The work in this proposal will determine the modulatory role of dopamine on ORNs and will provide insights into how peripheral dopaminergic pathways may be involved in disease-related reduced olfactory sensitivity.

This application requests funds for a conference of chemosensory scientists from universities in the Intermountain Region including Utah, Idaho, and Colorado. The conference will meet on February 9-12, 2001 at Jackson, Wyoming. Two outside speakers using novel functional imaging techniques will be invited. The meeting will be organized around three objectives: 1) presentation of innovative experimental techniques; 2) small group "brain storming" sessions to focus on identifying new directions for chemosensory studies applying the techniques described in the first objective; 3) establishment of collaborative projects.
The outcome of this meeting will be to establish new strategies for recording the functional activity of chemosensory neurons. Synthesis of cutting edge research findings from scientists studying organisms ranging from insects, cephalopods, amphibians, fish, mammals, and man will lead to exciting new advances in the field. A small number of participants with ample time for formal presentations and informal interactions will foster new collaborations and general sharing of expertise. Graduate students, post-docs and research associates will have full access to faculty and be encouraged to actively participate in all sessions. Efforts will be made to actively involve women and minorities in all aspects of the meeting.

DESCRIPTION (provided by applicant): The sensation of smell enables us to gain valuable information about a plethora of chemicals in our immediate environment, and to respond appropriately. Olfactory receptor neurons (ORNs) are responsible for detection of these chemicals and are unique among neurons because following death due to cytotoxic insults or viral infections, they are replaced by new ORNs. This process occurs in the olfactory epithelium (OE) lining the nose and involves the step-wise transformation of mitotic basal ("stem") cells into differentiated mature ORNs. In experiments outlined in this application, we will investigate the role of pituitary adenylate cyclase activating peptide (PACAP) in proliferation and maturation of normal developing and regenerating OE. PACAP is an intraepithelial peptide that acts as a cue for the regeneration of ORNs and for initiating defensive responses within ORNs to minimize cell death or apoptosis. The interaction of the signaling pathways activated by cell-extrinsic PACAP and cell-intrinsic electrical activity of ORNs in promoting differentiation of progenitor cells into differentiated ORNs will be investigated. In three specific aims, we will determine: (1) the expression profiles of PACAP and isoforms of its receptor (PAC1) in the developing and adult OE of wild-type and PACAP ko mice with and without bulb ablation; (2) the contributions of PACAP and cell-intrinsic activity in driving the maturation of ORNs and proliferation of basal stem cells, and (3) how PACAP prevents apoptosis of ORNs following cytokine inundation of the OE and injury caused by bulb ablation. Our studies are timely and critical for gaining an understanding of the cellular and signaling mechanisms involved in neuroregeneration in general, and are directly relevant to addressing the causes and potentials remedies of neurodegenerative diseases such as Alzheimer's and Parkinson's disease in which olfactory dysfunction is an early symptom.

[unreadable] DESCRIPTION (provided by applicant): This application requests training support for exceptional predoctoral students in the University of Utah's Interdepartmental Program in Neuroscience. The Program consists of structured interdisciplinary training in neuroscience followed by individualized research training under the guidance of 56 faculty members who work in one of 13 academic departments participating in the Neuroscience Program. The Program Director and interdepartmental Directorate will select the trainees, monitor their progress, and select and oversee the training faculty. Training will be provided in a broad range of areas including cellular neuroscience, molecular neuroscience, neurobiology of disease, brain and behavior, and developmental neurobiology. Prospective predoctoral trainees are admitted by the interdepartmental admissions committee of the Program in Neuroscience. During their first two years, Ph.D. students must take a series of interdepartmental core courses, perform laboratory rotations (with opportunities to work in both academic and industrial settings), and complete their Ph.D. qualifying examinations. A research advisor and thesis project are chosen after their first year. The majority of training will focus on individual research projects. The participation of 13 departments provides the opportunity for diverse interdisciplinary training in Neuroscience. A coherent structure is provided by the wide variety of interdepartmental activities sponsored by the Program in Neuroscience, as well as the long history of cooperation within the Neuroscience community here. In addition, all trainees will participate in a Responsible Conduct of Research course, a course in Scientific Writing and Speaking, and an annual retreat and regular research symposia where they will share their research results. This will be supplemented with vigorous seminar programs, journal clubs, and inter-laboratory research-in-progress group meetings to ensure that our students receive strong training in neuroscience, preparing them to contribute effectively to high-quality research programs. [unreadable] [unreadable] [unreadable]