Dose-related effects of central noradrenaline stimulation on behavioural arousal in rats

The general activity of rats in an open field test situation was observed following the central administration of isotonic saline and 0.5 and 2.0 mug of noradrenaline into the locus coeruleus. A significant increase in activity was found following the 0.5 mug, but not the 2.0 mug dose. The results are consistent with other reports indicating that low doses of centrally administered noradrenaline produce behavioural arousal whereas higher doses may result in behavioural depression. In addition, these findings suggest that the noradrenergic neurons arising from the locus coeruleus may be important for the arousal status of rats.