[A comparison of the frequency of the Straub tail elevation reaction as a measure of the activity of the endogenous opiate system in rats of different strains].

Stress-induced and exploratory activity-related Straub tail elevation was studied as a probable measure of endogenous opiate system activity in rats from catalepsy-susceptible GC strain as well as PM+ and PM- strains bred from Wistar stock for the presence and absence of predisposition to a stereotyped hyperkinesis with pendulum-like movements. All the three strains were characterized by lower incidence of Straub tail elevation than in the control Wistar stock. Moreover, the PM+ strain demonstrated a lower incidence of the studied reaction than PM- the difference between the strains being manifested during exploratory activity but not in immobilization stress.