The Journal of Neurophysiology Vol. 81 No. 3 March 1999, pp. 1147-1149
Copyright ©1999 by the American Physiological Society

Increased Intracellular Calcium in Rat Anterior Piriform Cortex in Response to Threonine After Threonine Deprivation

 ¹Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine and Food Intake Laboratory, University of California, Davis, California 95616; and  ²Pfizer Research, Groton, Connecticut 06340

Magrum, Linda J., M. Anne Hickman, and Dorothy W. Gietzen. Increased intracellular calcium in rat anterior piriform cortex in response to threonine after threonine deprivation The anterior piriform cortex (APC) may serve as the chemosensor for amino acid (AA) deficiency in rats. To investigate the mechanism by which the APC recognizes a limiting indispensable AA (IAA), we examined changes in intracellular calcium ([Ca²⁺]_i) in APC slices after culture in medium with or without threonine (Thr) or lysine (Lys). The addition of 1 or 10 mM Thr to slices previously incubated in Thr-devoid medium resulted in a significant and sustained increase in [Ca²⁺]_i compared to control slices; an effect not seen when isoleucine, another IAA, was added. Similar results were seen when lysine, but not threonine, was added to slices incubated in lysine-devoid medium. The rise in [Ca²⁺]_i resulting from the addition of the limiting IAA to deficient slices may be linked to enhanced activity of the appropriate AA transporter. This is suggested by preliminary findings that serine, a small neutral AA that uses the same transporter as threonine, gave rise to an enhanced response in the Thr-deficient slice.