RECOGNITION OF DEFICIENT NUTRIENT INTAKE IN THE BRAIN OF RAT WITH L-LYSINE DEFICIENCY MONITORED BY FUNCTIONAL MAGNETIC-RESONANCE-IMAGING, ELECTROPHYSIOLOGICALLY AND BEHAVIORALLY

Each L-amino acid (AA) in plasma and brain remains unchanged all day l ong while normal diet is available. But once restriction of L-lysine ( Lys) was introduced, strong anorexia happened. When Lys deficient diet was offered to rats, their growth were decreased depending upon dieta ry Lys intake, and they ingested Lys solution in choice quantitatively and both appetite and growth normalized. The recognition site for the deficit in rat's brain was identified by brain oxygenation using a fu nctional MRI that higher signals in the ventromedial hypothalamus and lateral hypothalamic area (LHA) appeared, at 30-50 minutes after Lys i njection i.p. and then recovered. Degree of Lys hunger, assayed by bar -pressing (50mg pellet of normal diet/30 presses), was suppressed by L ys micro-injection into the LHA, similar to free Lys ingestion but any other AA never did, suggesting the LHA as recognition site for Lys de ficit in rats with Lys deficiency due to AA homeostasis.