Atipamezole, an alpha 2 antagonist, stabilizes age-related high-voltage spindle and passive avoidance defects

The present study investigates the effects of an alpha 2 antagonist, atipamezole (Ati), on the high-voltage spindle (HVS; Ati at 0.1, 1.0, and 3.0 mg/kg) activity, passive avoidance retention (PA; Ati at 3 mg/kg; injected before retention trial), and water maze (WM; Ati at 3 mg/kg; injected after daily training trials) acquisition of young and aged rats. PA retention trial performance defect of aged rats was partially alleviated by Ati at a 3-mg/kg dose. Ati at 3 mg/kg had no effect on the PA performance of young rats. Retention trial performance of nonshocked young or aged rats was not altered by a 3-mg/kg Ati dose. WM acquisition was not affected by posttraining Ati injections. Age-related increase of HVS was stabilized by Ati at 1 or 3 mg/kg. Ati at 1 and 3 mg/kg completely suppressed HVS of young rats. Ati at 0.1 mg/kg had no effect on HVS of young or aged rats. The results suggest that alpha 2-antagonist-administration-induced increase in noradrenergic activity may stabilize age-related HVS activity increase and PA performance defect.