Lactating rats were given distilled water or distilled water containing 0.067% lead chloride (500 ppm lead) as their sole source of drinking fluid from Days 1-21 of lactation. Activity, social investigation and rough and tumble play fighting behaviors of the offspring were observed on Day 26 and activity and play solicitation behaviors on Day 36. Although lead treatment reduced the mothers' fluid intake, there were no effects on pup growth and activity or on maternal behaviors. When paired with a group-housed stimulus animal on Day 26, lead-treated subjects had increases in the two measures of play fighting (crossover and pinning), and in social investigation, relative to controls. When tested with a scopolamine-treated, non-playful stimulus on Day 36, increased crossover frequencies were observed in lead-treated subjects when compared with controls. Two-min activity levels on Days 26 and 35 were unaffected by lead exposure. These results indicate that social interactive behaviors of juvenile rats are effective tools in the assessment of exposure to toxic substances early in development.

Aggression↗

PubMedDate not supplied

Social memory deficits in adult male rats exposed to cadmium in infancy.

In two experiments infant rats were injected subcutaneously with 0, 1, or 2 mg Cd/kg on Day 5 or 6 after birth. In adulthood (150 days of age) subjects in both experiments who received the 2 mg/kg dose failed to learn the identity of a strange rat in a social recognition test. Cadmium-treated rats investigated familiar and strange rats equally, whereas control subjects investigated familiar rats much less than unfamiliar individuals. Results with rats in the 1 mg/kg group were less consistent; in Experiment 1 they failed to learn the identity of a stranger, in Experiment 2 they behaved like controls. The level of investigation of a strange rat did not differ among the experimental groups, indicating cadmium did not cause a performance deficit. The 2 mg/kg dose of cadmium had no effect on body weight in Experiment 1 and a small (6.98%), but significant, depressant effect on body weight in Experiment 2. Cadmium exposure in infancy appears to affect social memory processes long after the treatment period.

Animals↗

PubMedDate not supplied

Cadmium exposure in infancy: effects on activity and social behaviors of juvenile rats.

In two experiments male and female infant rats were given single injections of cadmium chloride (0, 1, 2, 3 or 4 mg Cd/kg) on Day 5 or 6. Animals receiving the 3 and 4 mg/kg doses had high mortality rates at weaning; survivors were extremely underweight and were not used in postweaning tests. Male subjects receiving 2 mg/kg in infancy were significantly more active after weaning than littermates who had received 0 or 1 mg/kg doses, and on Day 29 they also engaged in significantly more rough and tumble play with a nontreated partner than did rats in the other groups. This effect of early cadmium exposure was also evident when males were tested with similarly treated subjects on Day 44: rats in the 2 mg/kg group had higher pinning frequencies than rats in the 0 or 1 mg/kg groups. In contrast, females in the 1 and 2 mg/kg groups did not have increased activity or rough and tumble play fighting. These data are consistent with the few correlational studies in human children which suggest changes in social behaviors associated with elevated tissue cadmium levels.

Animals↗

PubMedDate not supplied

Acute and chronic caffeine exposure effects on play fighting in the juvenile rat.

Effects of acute and chronic exposure to caffeine on the behavior of juvenile rats were assessed in three experiments. In Experiment 1, two indices of play fighting--pin frequency and duration--were decreased and locomotor activity was increased in dose dependent fashions by caffeine. Social investigation of another juvenile was not affected by the drug. In Experiment 2, juvenile rats were isolated and given caffeine in their drinking fluid for 10-11 days. Play fighting was increased by all except the highest caffeine dose. In Experiment 3, juveniles were housed in groups of four and received either tap water or caffeine in their drinking fluid. Pin frequency of caffeine treated subjects was lower than controls on days 2-4, and higher than controls on days 9-11 after caffeine treatment was initiated. Evidently, caffeine has inhibitory and facilitatory effects on juvenile play fighting behavior, contingent on duration of exposure to the drug.

Aggression↗

PubMedDate not supplied

Caffeine and social investigation in the adult male rat.

In three experiments with adult rats, caffeine (0, 10, 20, 40 mg/kg) was found to increase the social investigation of a novel juvenile conspecific. Activity was elevated only after caffeine injections, whereas the duration of social investigation was raised after both the injection of caffeine and the administration of caffeine via the drinking water, suggesting the mechanisms of action of caffeine on these two behaviors may be independent. Duration and frequency of investigation were each increased following caffeine exposure, but the amount of investigation/episode was not influenced by this substance. Finally, the acute response to caffeine was not altered by prior exposure to the methylxanthine in the subject's drinking water.

Analysis of Variance↗

PubMedDate not supplied

Caffeine: effects on the behaviors of juvenile rats.

Caffeine, a central nervous system stimulant, was found to alter the expression of 3 behaviors in the juvenile rat. After caffeine administration, locomotor activity was increased in rats of all ages studied (24-84 days old). Pinning, a behavior characteristic of the juvenile period and used as an index of play-fighting, was suppressed following caffeine exposure, but only in rats 24-54 days old. Social investigation was not affected by caffeine in 24- and 34-day-old rats. However, in animals 44-84 days of age caffeine increased both the frequency and duration of investigation of a novel juvenile. Although caffeine influenced all the behaviors we observed, the developmental time course of caffeine's effects was different for each behavior.

Analysis of Variance↗