It is known that animal learning ability depends on the level of anxiety [1]. There is special interest whether such dependence influences on learning disturbances in postresuscitation period after haemorrhagic shock (HS) and what manner those disorders develop taking into consideration the starting functional CNS state. This research led to the finding that there are several stages in development of postshock learning disturbances.

Previously rats were placed in an elevated plus maze to determine their anxiety level. In 2 days anaesthetized rats were subjected to HS. Animals were rapidly bled to a mean arterial pressure of 40 mm Hg. Blood refletting or reinfusion was instituted to maintain this pressure for one hour followed by retransfusion with all shed blood. Rat learning was studied in a food-rewarded T maze (4 days of training sessions of 5 trials each) in a week and in a month after HS. Intact and operated rats were control. The program Statistica was used for data calculation.

In the intact group, the correlation coefficients between starting anxiety level and learning parameters as latency and time of correct trials in the first day of training were 0.45 and 0.44, respectively. Probably the low correlation coefficients can be explained by the long time between starting test in elevated plus maze and learning in T maze, preliminary adaptation and handling. Such correlation was not in the other days. In the operated group there is no sufficient correlation between starting anxiety level and learning ability. At the same time in HS group sufficient correlation was found between starting anxiety level in one hand and latency, time of correct trials and number of correct trials in the other hand (Spearman coefficients: 0.52; 0.47; 0.49, respectively, P<0.05) in 1st, 2nd and 3rd day sessions in T maze in a week after HS. Thus, learning disturbances in this period depends on starting CNS functional state. As long as behavior of intact animals depends on their starting functional state we divide animals to 2 groups concerning starting anxiety. All data in the other groups were standardized relatively these intact groups to determine learning disorders dependence on starting functional CNS state. Latency and time of correct trials increased in HS group by comparison with control groups on 3rd and 4th learning days in T maze in a week. However the number of correct trials in this group did not change relative to control. So the learning process slowed down. This is very likely to be caused by a change of perception. It is important only animals with low starting anxiety level had such disorders. In a month after haemorrhagic shock there were not correlations between starting anxiety level and learning disturbances. Besides learning curve of rats subjected to HS in T maze during 4 days of training had strong divergence from that of intact and operated animals. In intact and operated groups latency and time of correct trials decreased and number of correct trials raised from 1st to 4th day of training while in HS group such process was not observed.

Thus, pathological processes developing in postshock period lead to the consolidation of memory track becomes weak. In conclusion measuring correlation coefficients between starting anxiety level and learning parameters in T maze showed existence of several stages in learning disturbances after HS.

References

1. Zhukov; Vinogradova (1994)