Mast cells are a class of cells found in the brain that are not themselves nerve cells, or neurons. Although often associated with allergies, they are present in normal brains. Their numbers can change in adults as a result of hormonal changes, and there is molecular evidence that mast cell secretions can affect long-term modifications of excitability of nerve cells. A novel recent hypothesis, based on some preliminary data from birds, is that mast cells may be small migratory glandular units, capable releasing compounds with neurotransmitter or modulator activity. Release of compounds from mast cells appears to be different from release of neurotransmitter from nerve cells; in mast cells granules appear to form within the cell and may fuse to form large secretion chambers, or sometimes much smaller releases are seen. This Small Grant for Exploratory Research (SGER) supports studies to develop electron microscopical techniques to substantiate how this novel release mechanism occurs, to compare observations on mammals with prior observations on birds, and to add histochemical techniques to determine what compounds may be passed from mast cells to neurons. Results will have a substantial impact beyond neuroendocrinology because mast cells occur in all vertebrate brains, and these mechanisms could be very important for understanding the plasticity of neuronal function in the brain. A novel form of cellular secretion also will be important to general cell biology.
