[Individual differences in the reactions to acute stress related to behavioral types. The structural changes in the brain].

Structural alterations in the brain after stress were studied in rats with different behavior type in open field and forced swimming tests. The most typical brain reaction to acute stress was a combination of reactive (hypertrophy and fission of mitochondria, hyperplasia of rough reticulum) and destructive (disintegration of mitochondria and rough reticulum) alterations which were different in rats with various behavior types. Thus, in rats with the active type of behavior showing the greatest resistance to stress (see report 1) the reactive processes were more manifest, while the the rats with the passive type of behavior showing lower resistance to stress developed destructive processes. Rats of the middle group with the least resistance to stress differed from the other two groups by vague structural alterations, i.e. by the lack of evident predominance of any definite process. It is assumed that individual differences in the resistance to acute stress are associated with individual differences in the manifestation of reactive alterations in the brain which can be regarded as a structural component of the urgent adaptation to stress.