Document Type

Dissertation

Date of Award

1976

Keywords

Developmental psychobiology, Malnutrition, Brain damage Brain, Wounds and injuries

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

First Advisor

P. J. Donovick

Second Advisor

R. G. Burright

Third Advisor

C. F. Cegavske

Abstract

Transient hypoxia or hypoglycemia in the neonate frequently leads to permanent neural damage. In developing countries, malnutrition is likely to be superimposed upon such damage. Using septal lesions as a tool, we attempted to assess the interaction between neonatal brain damage and subsequent malnutrition.

Half of the offspring of each sex in each of 28 litters of albino rats received lesions restricted to the septum at 24 hours of age. The other half underwent only the hypothermia (anesthesia) phase of the surgical procedure. Following surgery, pups were returned to their mother and left undisturbed until 10 days of age, when maternal retrieval tests were conducted and showed no differential preference for control or operated pups. At weaning (25 days of age) no significant differences among groups were found either in terms of activity or the number of transitions between levels of a 2-tier open field.

Immediately following open field testing, rats were assigned to housing and nutritional conditions such that a 2 x 2 x 2 x 2 completely randomized factorial design was attained. Four subjects of the same sex were housed in a cage, such that all rats in the cage had the same neonatal surgical treatment (i.e., 4 septals or 4 controls) or mixed neonatal surgical treatment (2 septals and 2 controls in the same cage). Half the subjects in each of these conditions received a commercially prepared diet with 8% protein while the other half received a comparable diet with 27% protein. These dietary conditions were maintained for 5 weeks, at which time half of each of the 16 groups were sacrificed for organ weights and histological purposes. The other half of the animals were housed singly and allowed 7 weeks of undisturbed recovery on a diet of Purina laboratory rat chow.

Those rats maintained on 8% protein and sacrificed at 60 days of age exhibited smaller absolute wet weights of whole brain, adrenal glands, liver, spleen and gonads. However, 8% protein animals had heavier brains and adrenals relative to their body weight. The higher adrenal weight/body weight ratio was more pronounced in males, particularly those without neonatal septal lesions.

Subsequent to the 7-week dietary recovery period on Purina chow rats remaining in the experiment were tested in a battery of behavioral tests. In the open field, whereas female septals were more active than female controls, there was no lesion effect in males. Malnutrition did not appreciably alter activity, but mixed housing generally resulted in increased activity across treatments. In response to a flashing light, male activity was suppressed to a greater extent than that of females. Across sex, malnourished septal rats suppressed their activity less if they had been housed under the mixed condition. In a passive avoidance task utilizing shock as the aversive stimulus, no differences between groups were observed. These data point to an important degree of interaction between sex, neonatal septal lesions, malnutrition and housing conditions in determining subsequent behavior.

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