EFFECT OF LONG-TERM ACETYL-L-CARNITINE ON STRESS-INDUCED ANALGESIA INTHE AGING RAT

Cold water swim (CWS) analgesia in the rat is mediated by the hypo-tha lmo-pituitary-adrenocortical (HPA) axis. An age-dependent increase of CWS-induced analgesia was observed in male Sprague-Dawley young (4 mon ths), adult (15 months) and old (26 months) rats. Acetyl-L-Carnitine ( ALCAR) chronically administered (75 mg/kg/daily in drinking water for 8 months) to old rats was able to maintain the stress-dependent respon se at the same levels as in adult rats. This effect may be explained b y ALCAR capability of retarding the age-dependent loss of glucocortico id receptors in the hippocampus, thus maintaining the glucocorticoid c ompetence of this structure which exerts a negative feedback control o ver the HPA axis activity.