Research

INDIVIDUAL RESEARCHER

Allan S. Schneider , Ph.D.
Professor Emeritus
e-mail: schneia@mail.amc.edu

Education

1968 - Ph.D. from University of California, Berkeley

Current Research

The research program of this laboratory is focused in two areas: 1. Calcium Signaling and Catecholamine Neurotransmitter Release from Adrenal Chromaffin Cells The adrenal medullary chromaffin cell is a classic neurosecretory cell mediating the sympatho-adrenal acute stress or "fight or flight" response. The chromaffin cells are developmentally homologus with sympathetic neurons in their synthesis, storage and secretion of catecholamine and enkephalin neurohormones. This laboratory is investigating the mechanisms regulating the cytosolic calcium signal for neurosecretion in active secretory zones along the inner plasma membrane. We are investigating several aspects of local calcium homeostasis below the plasma membrane including effects of spatial distribution of Ca2+ channels, the role of mobile and immobile Ca2+ buffers, subcellular diffusional obstacles and Ca2+ efflux by Na-Ca exchange. Computational modeling of the submembrane Ca2+ signal is being used to fit experimental single cell Ca2+ fluorescence imaging data in an effort to determine the properties of endogenous Ca2+ buffers, which in turn control the spatiotemporal properties of the Ca2+ signal at sites of exocytotic neurotransmitter release. 2. Fetal Nicotine Syndrome and the Role of Nicotinic Acetylcholine Receptors in Cerebral Cortical Development There is an extensive literature showing that fetal nicotine exposure, due to maternal smoking, alters embryonic brain development and results in a variety of pathological effects in the neonate that fall under the heading of the fetal nicotine syndrome. These include a fourfold increased incidence of SIDS, ten's of thousands of cases of tobacco induced abortions, premature deliveries, low birth weight and an increased incidence of attention-deficit hyperactivity disorder. Although the mechanisms involved are not well understood, they are thought to be mediated in part by nicotinic acetylcholine receptors in the fetal brain. Yet neither the existence of functional nicotinic receptors in early embryonic mammalian brain nor their role in development have been established. We have obtained electrophysiological and Ca2+ signaling data indicating that functional nicotinic receptors are expressed on mouse cerebral cortical cells at early embryonic ages when the cortex consists mainly of dividing stem and progenitor cells. These findings now open up an interesting set of questions concerning the role nicotinic acetylcholine receptors play in early cortical development and the mechanisms underlying how chronic fetal nicotine exposure during maternal smoking may alter such development and lead to the fetal nicotine syndrome. Resolution of these issues forms the long-term goals of this project. We are also interested in the cellular mechanisms contributing to nicotine tolerance and dependence including neuronal adaptive responses to chronic nicotine exposure.

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References

1. MAH, S.J.M, TANG, Y., LIAUW, P.E., NAGEL, J.E. and SCHNEIDER, A.S.,Ibogaine acts at the nicotinc receptor to inhibit catecholamine relese. Brain Research 797,173-180(1998)



2. TANG,Y.M., TRAVIS, E.R., WIGHTMAN, R.M. and SCHNEIDER, A.S., Na-Ca Exchange affects the local Ca signal and the rate of exocytotic secretion in single bovine adrenal chromaffin cells. J. Neurochem.74, 702-710 (2000).



3. ATLURI, P., FLECK, M.W., SHEN, Q., MAH, S.J., STADFELT, D., BARNES, W., GODERIE, S., TEMPLE, S. and SCHNEIDER, A.S., Functional nicotinic acetylcholine receptor expression in stem and progenitor cells of the early embryonic mouse cerebral cortex. Develop. Biol. 240: 143-156 (2001)



4. SCHNEIDER, A.S., MAH, S.J., FARHADI, M., GRINDE, E. and DAVIS, K Calcium transport proteins in active secretory zones: Na/Ca exchange isoforms and kinetic properties in chromaffin granule and plasma membranes. Ann. N. Y. Acad. Sci. 971: 142-144 (2002)



5. SCHNEIDER, A.S., DAVIS, T.E. AND MORARU, I. The Virtual Chromaffin Cell: Simulating Ca2+ transients in active secretory zones. In: Cell Biology of the Chromaffin Cell (L. Gandia and R. Borges, eds), Inst.Teofilo Hernando, Spain, Chap 29, pp.197-203. (2004) Also available on line: http://webpages.ull.es/users/isccb12/