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The effects of N-feruloylserotonins, substances isolated from the seeds of Leuzea carthamoides (WILLD.) DC., on nociception and anxiety were studied in Wistar rats. Nociceptive responses were measured using the plantar and tail-flick tests which were administered before and after swimming stress (3 min, water temperature 32 degrees C). Anxiety was evaluated using an elevated plus maze. In Experiment I, neither basal nociception nor stress-induced analgesia was influenced significantly. Separating the animals into groups based on their basal nociceptive sensitivity, either high- or low-pain threshold revealed that N-feruloylserotonins have selective effects, especially on rats with high-pain thresholds. In these animals, N-feruloylserotonins reduced the stress-induced analgesia that followed swimming stress. In Experiment II, basal nociceptive sensitivity correlated with indicators of anxiety; high-pain threshold rats were more anxious in the elevated plus maze, with less frequent visits to open arms. The opposite effect was seen in low-pain threshold rats. N-feruloylserotonins did not influence anxiety in low-pain threshold rats, although it reduced anxiety in the high-pain threshold rats as indicated by the increased ratio of open arm visit frequency compared to closed arm visit frequency in the elevated plus maze. From these results we concluded that N-feruloylserotonins have selective stress-reducing effects in stress-sensitive animals.

The effect of stress anticipation was studied in two inbred Wistar rat strains with high and low sensitivity to isoprenaline. The animals were exposed to tail-flick and 4-hr water immersion restraint stress on two consecutive days. On the first day stress was applied to one group and the next day to the anticipation group. The changes in adrenal, heart and spleen weights, tail-flick latency, incidence of gastric ulcers, and the antioxidant defense system in the sensorimotor cortex were compared with two non-stressed control groups. Anticipatory stress decreased adrenal weights. The content of thiobarbituric acid reactive substances (TBARS) was increased both in acute and anticipatory stress; superoxide dismutase, glutathione peroxidase, and antioxidative capacity were increased in anticipatory stress only. Stress anticipation decreased the pain threshold in the isoprenaline-sensitive and increased in the isoprenaline-resistant rats and led to more frequent gastric ulcers in the isoprenaline-resistant group. Significant sex differences were observed both in adrenal weights and TBARS content. The relative adrenal weights were negatively correlated with the TBARS content. We suggest that the outcome of anticipatory stress may depend upon the relation between the hormonal and antioxidant functions of the adrenals and that anticipation-induced activation of antioxidant enzymes may ameliorate the acute stress response. Anticipation itself was found to be a stronger stressor than physical acute stress.

The effect of various stressors of different intensity applied in random order before the final single immersion restraint stress was tested in two inbred rat strains, isoprenaline-sensitive and isoprenaline-resistant. The isoprenaline-sensitive strain revealed higher incidence of heart lesions after this single acute stress and low incidence of gastric lesions. The isoprenaline-resistant strain had the opposite characteristics. These differences were constantly reproducible when this strong stressor was used. After prestress by different stressors (tail-flick, ether anaesthesia, Porsolt swimming stress) at different time schedules, the incidence of gastric ulcer lesions, the weight of organs (heart, adrenals, spleen) changed substantially in isoprenaline-sensitive rats only. The most important result was reversal of the extent of gastric lesions. The isoprenaline-sensitive strain revealed more lesions than the isoprenaline-resistant one. The repeated different prestressors mainly changed the reactivity of animals, isoprenaline-sensitive rats becoming more similar to isoprenaline-resistant rats. These findings urged us to interpret carefully the results obtained in stress research with different and multiple stressors both in animals and humans.

Behavioral pattern was studied in two inbred strains of rats which have different responses to stress. These strains were originally developed from a randomly bred Wistar rat colony, according to high or low myocardial cells sensitivity to cardiotoxic effect of isoprenaline. One strain is very sensitive to isoprenaline cardiotoxicity (IS = isoprenaline sensitive) the other strain is more resistant (IR = isoprenaline resistant). In the IR strain the immobilization immersion stress causes high incidence of gastric ulcers, while the IS strain is prone to heart pathology. In this communication we report the differences in behavior of these two rat lines in three tests: open field, intruder's test and Porsolt's forced swimming test. The IS animals were passive and anxious in open field test, submissive in intruders test and they showed more floating time in Porsolt's forced swimming test. The IR rats were active, aggressive and dominant.

Two inbred rat strains were obtained by selective breeding and inbreeding: IR (isoprenaline resistant) and IS (isoprenaline sensitive). In addition to known differences between the two strains (1) other differences were found. As compared to IS strain, IR rats were more aggressive and showed more comfort behaviour in open field test. IR rats developed larger stress-induced gastric lesions but smaller heart lesions. They had larger spleen and thymus and more severe arthritis after Freund adjuvans administration. The two strains might be useful in studying the effects of drugs on various pathological processes. Their hybrids are being used to study interrelations between different genetic factors.

Elevation of lipid peroxidation (LOX) was observed in rabbits and mice after the intravenous administration of 0.2 micrograms.kg-1 of lipopolysaccharide (LPS) and 100 micrograms.kg-1 of peptidoglycan (MP). The peak was reached sooner after peptidoglycan, and 2-4 h after LPS administration. The trends of lipid peroxidation were the same in both species. 8-10 h later original LOX blood levels were reached. Mild horizontal vibration (1 h) induced in both species a significant lowering of LOX. This appeared already immediately after the vibration. Original values were gained again after 8-10 h. The difference between the internal stressors, LPS and MP, and the external stressor, vibration, are discussed.

During 6 h the plasma level of salicylates was followed after oral administration of aspirin. The plasma levels of salicylic acid were significantly lower in bull than in heifer calves during the whole observation period. The toxicity of the drug was higher in female animals.