Effect of aging on psychological stress-induced increases in noradrenaline release in the rat anterior hypothalamus: an in vivo microdialysis study.

Basal and psychological stress-induced noradrenaline (NA) release were studied by intracerebral microdialysis in the hypothalamus of rats aged 9 weeks or 12 months. Basal NA output was not significantly different between young (9-week-old; 2.11 +/- 0.22 pg/20 min) and aged (12-month-old; 2.29 +/- 0.34 pg/20 min) rats. Psychological stress for 20 min significantly increased NA release in both groups (186% and 142% of baseline at 9 weeks old and 12 months old, respectively); however, the increase in aged rats was significantly lower than that in young rats (P < 0.01). This finding suggest that the noradrenergic neuronal response to psychological stress is attenuated in aged rats.