B. Michael Thorne

No change in emotionality of rats following bulbectomy

An attempt to replicate the hyperemotionality syndrome seen in rats following olfactory bulb ablation was unsuccessful, despite the use of a single-blind testing procedure and seven response measures. No difference in postoperative emotionality was found when males and females were compared. Procedural differences were discussed which might account for the failure of the present study to replicate previous results.

Aluminum ingestion and behavior in the Long-Evans rat ☆

A variety of behaviors was measured in adult Long-Evans male rats fed ground rat chow containing either no added aluminum, low aluminum (1500 mg/kg), moderate aluminum (2500 mg/kg), or high aluminum (3500 mg/kg). There were no effects of aluminum on either body weight or mouse killing. There was an inverse relationship between brain aluminum and open-field activity. Elevated brain aluminum was correlated with relatively poor performance on a single-trial passive-avoidance task and on a visual discrimination with reversal task.

Olfactory system damage in rats and emotional, muricidal, and rat pup killing behavior

Long-Evans female rats were subjected to a variety of olfactory-system lesions and compared with septally damaged and operated-control Ss in terms of handling characteristics, muricidal behavior, and behavior toward rat pups. Damage to the olfactory bulb rostral to the frontal poles resulted in increased mouse killing without changes in E-directed behavior. Additional damage under the frontal lobes increased both emotional behavior and mouse killing. Olfactory tubercle damage unaccompanied by olfactory bulb removal failed to produce either increased emotionality or mouse killing. A trend toward an increase in rat pup killing was noted in rats sustaining olfactory bulb damage. Finally, rats with septal damage, although extremely difficult to handle, did not display increased muricidal behavior.

Long term effects of dietary copper and sodium upon blood pressure in the long-evans rat

Abstract Forty-eight male Long-Evans rats were divided into three groups of 16 and assigned to one of the following levels of dietary copper at weaning: 1) low copper (LC), no added copper; 2) marginal copper (MC), 3 mg Cu/kg feed; 3) adequate copper (AC), 8 mg Cu/kg feed. At 100 days of age, half of the rats in each group were fed 5% NaCl in their drinking water for 1 week, followed by 1% NaCl for an additional 11 weeks. The other half were fed deionized-distilled water for the same time period. Systolic blood pressure was measured biweekly from day 100 until the rats were 6 months old. The copper deficiency of rats in the LC group was confirmed by a decrease in growth rate, a decrease in hematocrit and hemoglobin levels, and an increase in serum cholesterol levels. Copper deficient rats also had higher levels of serum triglycerides and glucose, but lower high density lipoprotein cholesterol as a percentage of total cholesterol than AC and MC animals. The results from this study also indicated that LC and MC rats had lower blood pressure than AC rats. The addition of 5% NaCl to drinking water increased blood pressure whereas 1% NaCl did not have the same effect.

Septal damage and muricide: Effects of strain and handling ☆

Abstract Rats from two strains (Long-Evans and Sprague-Dawley) were subjected to either septal ablations or sham operations and were either handled or not handled for the first four postoperative days. On the fifth day all animals were tested for muricidal behavior using albino mice. L-E rats showed a greater tendency to kill than S-D rats. Additionally, septal lesions increased the probability of muricide in the L-E strain while no difference was observed in S-D rats. Finally, handling had no effect upon the expression of muricide.

Brainstem reticular formation lesions: Amnestic effects on learned habits in the rat

Adult albino rats, previously overtrained on a brightness and a pattern discrimination habit, sustained bilateral lesions to the brainstem reticular formation and were subsequently tested for retention. Those groups receiving lesions to the basolateral mesencephalic reticular formation or to the paramedial portion of the reticular formation at either the dimesencephalic juncture, mes-metencephalic juncture, or rostral pontine levels exhibited significant losses in retention of the pattern habit. Lesions destroying either the dorsomedial mesencephalic reticular formation or brainstem areas dorsal, lateral, or ventral to the reticular formation failed to produce significant retention deficits on either habit. Similar findings were obtained in connection with the retention of a nonvisual (kinesthetic) discrimination habit.

Memory deficit in passive-avoidance learning in bulbectomized Long-Evans hooded rats ☆

Male and female Long-Evans hooded rats were subjected to either olfactory bulb damage or control surgery. Olfactory bulb removal resulted in increased mouse killing, increased irritability to handling, and increased open-field activity. In acquisition trials on a modified passive-avoidance apparatus, control animals habituated rapidly to the apparatus, while OB rats showed little evidence for habituation. All controls showed 24-hour retention of shock on the last acquisition trial, while OB rats showed the typical retention deficit, despite being given a behavioral alternative to withholding a response. The P-A deficit in OB rats appears to be a learning/memory deficit, not the result of heightened activity.

The effects of food deprivation and the length of the test on muricide in rats

Abstract Long-Evans hooded rats were divided into three feeding conditions: ad lib, deprivation, or deprivation/ad lib. Approximately one-half of the animals received a 5-min mouse-killing test while the remaining animals received a 20-min, 24-hr mouse-killing test. Results indicate that food deprivation is a powerful determinant of the initiation of mouse killing in rats, but subsequent maintenance of the killing response is less dependent of feeding schedules. The probability of mouse killing is not affected by shifting deprived rats to an ad lib feeding schedule; however, response latencies are significantly increased by this manipulation. In addition, the results of this study indicate the need for future research to determine a standard and optimum mouse-killing test duration.

Aluminum toxicity and behavior in the weanling Long-Evans rat

Muricidal behavior, weight, open-field activity, passive-avoidance learning, and learning of an eight-arm radial maze were assessed in Long-Evans hooded rats subjected as weanlings to 60 days of oral administration of aluminum hydroxide gel (Group AA) or tap water (Group NA). Measurement of brain aluminum content indicated that the groups did not differ significantly in neural incorporation of aluminum, although the median amount of aluminum in each brain area examined was higher for Group AA than for Group NA. Although the highest brain concentrations of aluminum were found in the hippocampus, there was no evidence for cognitive impairment in the present study. Aluminum-exposed rats weighed less than nonexposed animals at all weight periods, probably reflecting their initially decreased fluid intake. There was slight evidence for activity changes as a function of brain aluminum content. Age of the animals appears to be an important consideration in the study of aluminum toxicity in rats, with young animals less affected than older animals.

Omission training and extinction in rats with septal damage

Rats with either control operations or septal damage were pretrained on a VI 30-sec schedule and tested for response suppression ability on either an omission training (OT) task or on extinction. Septal damage enhanced barpressing on the VI 30-sec task. Animals with septal damage took longer to suppress responding on the OT task than controls while lesioned and control animals tested on extinction did not differ. Increased emotionality was seen in subjects with septal damage on the first test day but not thereafter. Animals tested with OT suppressed responding more rapidly than animals tested on extinction.