Strain differences in brain biogenic amines concentration in rats with different resistance to emotional stress

Blood pressure and heart rate were measured under the conditions of prolonged emotional stress due to 30 h immobilization in rats of various strain: 1. Wistar; 2. Veg (deviated from Wistar); 3. August; 4. Bastards. Some defined areas of brain from Wistar and August rats were dissected and used for the estimation of noradrenaline (NA) and dopamine (DA) content with the aid of spectrofluorimetric method. It was found that, among the animals of all strains used, different groups may be defined according to their resistance to cardiovascular changes due to emotional stress. Thus, the highest percentage of resistant animals was found among Wistar rats, while the lowest one occurred in August animals. Intact August rats differ from those of Wistar strain by a lower content of NA in hypothalamus and a higher content of DA in midbrain and isthmus. Sensitive animals of August strain showed an increase of DA content in hypothalamus and bulb compared to intact animals and a decrease of DA content compared to operated controls, while no such changes were observed in Wistar rats. However, sensitive Wistar rats showed an increase of DA content in midbrain.