Difference in the reactivity of the mesocortical dopaminergic neurons to stress in the BALB/C and C57 BL/6 mice

The sensitivity to electric foot shock strees of the dopaminergic system projecting to the frontal cortex was investigated in Balb/c and C57 BL/6 mice. Changes in the activity of the dopaminergic neurons were estimated by measuring DOPAC and DA levels in the frontal cortex using a radioenzymatic method. The DOPAC/DA ratio was enhanced in both strains as soon as 2 min after the beginning of the strees but the effect was much more pronounced in the Balb/c than in the C57 BL/6 mice. The difference was even more important after 6 min of stress since the DOPAC/DA ratios were respectively 380 and 200% the corresponding control values. These changes were related both to an increase of DOPAC levels and a reduction of those of DA. This difference in the reactivity of the mesocortical dopaminergic neurons could partly contribute to some of the distinct behavioral responses of these two strains of mice. A preliminary communication of these results was made at the 7th International Congress of Pharmacology (Paris, July 1978).