Donald O'Malley - US grants

9514777 O'Malley Calcium is a key signaling molecule in the nervous system of all animals. In vertebrate animals, calcium levels inside nerve cells increase when the cells are stimulated. Increased calcium levels have many different actions inside nerve cells, ranging from the immediate regulation of the electrical excitability of the cell to very long term changes in the cell's behavior, which may be mediated through alterations of gene expression. Recently a technique was developed that allows the imaging of calcium activity in nerve cells in the brain of intact zebrafish. This allows measurement of cellular calcium activity in response to a variety of sensory stimuli and also allows the investigation of any correlations between these calcium signals and the behavior of the fish. This approach demonstrated that calcium signals in one particular identified nerve cell in the hindbrain of the zebrafish, the Mauthner cell, were dramatically enhanced after repetitive sensory stimulation. One principal aim of this proposal is to determine the conditions required to produce this novel form of enhancement. This will be accomplished by varying the timing, intensity and modality of sensory stimulation. A second major aim is to understand the cellular mechanisms underlying these large calcium signals. A third aim takes advantage of the fact that the Mauthner cell is a behavioral command neuron, which triggers the animal's escape behavior. This cutting-edge project will demonstrate the molecular basis for a behavior in a living animal. The potential implications are enormous, both for the understanding of the molecular basis of animal behavior and for the development of non-invasive measuring techniques in living animals.

DESCRIPTION The reticulospinal system (RS) is a major descending motor control system. It has not been possible to specifically stimulate or lesion discrete functional subsets of RS neurons and so our understanding of RS signals being transmitted to the spinal cord is poorly understood. The transparent hindbrain of the larval Zebrafish which is accessible to optical techniques solves this problem. Further, the larvae's RS system is quite simple. It is comprised of about 100 neurons, most of which can be identified in the living fish. This allows both optical recording of neural activity and laser ablation of either individual neurons or subsets of neurons. Further, given the small total number of neurons, it is feasible to make precise ablations and quantify the effects on such larval behavior as swimming, escaping, feeding and more complex behaviors. Thus, the larval Zebrafish hindbrain provides an ideal opportunity for understanding the neural control of different behaviors. The first aim is to ablate all RS neurons to delimit the range of behaviors that the RS system mediates. The second aim will use optical recording and laser ablation to identify which specific RS neurons are involved in which locomotor behaviors. This will not only reveal the functional organization of the Zebrafish hindbrain but allow the evaluation of several competing hypotheses on the forms of network organization used to implement motor control.

0608892
Menon
The goal of this NER application is to develop nano-biodevices for recording and stimulating nerves that are reliable and long lasting. This exploratory proposal addresses some of the critical issues entailed. These issues include gold nano-wire size, cell growth and motion artifacts, and cell viability at the electrode-cell interface. The research plan calls for fabrication of an array of nano-wires in three sizes ranging of 50, 100, and 200 nm. Measurements will be performed by culturing two types of neural (rat hippocampal and human neuroblastoma) cells onto the surface of Au and peptide conjugated Au nano-wires.