The development of cerebral cortex in hypothyroid and starved rats

Abstract

ONE FIGUREBoth congenital hypothyroidism (Benda, '47) and chronic starvation during childhood (Keys, Broiek, Henschel, Michelson and Taylor, 'SO) cause a serious and permanent impairment to bodily growth, and in either condition the basal metabolic rate may be depressed to as much as 40% of the normal level. Thyroid deficiency and inanition also have similar effects on the development of the nervous system for, in the rat, the growth of the brain is retarded, but less severely than that of the body. I n each case, therefore, the experimental animal has a central nervous system which is heavier than would be expected for a normal animal of the same weight (Hammett, '26a). Furthermore, the brains of both hypothyroid (Hammett, '26b) and starved (Donaldson, ' 11 ; Hatai, '04) rats contain less water in relation to their size than the brains of normal animals of the same age.This similarity of effect applies equally to the maturation of behaviour in the rat. Biel ('39) showed that chronic starvation retarded the time of first appearance of a number of automatic reactions and similar results have been reported in cretinous rats (Eayrs and Taylor, '51). These findings suggested that the changes in cortical structure which are associated with impairment to the maturation of behaviour in the cretin, such as reduced myelination (Barrnett, '48) and closer aggregation of cell bodies (Eayrs and Taylor, '51) might also occur in the starved animal.

Maturation of somatomotor responses to strychnine in the albino rat

“…4, open circles). The descending part, characteristic of the immature animal, should be obtained in the pre-natal period, in view of the fact that at 30-35 days of gestation the guinea-pig presents a similar degree of maturity to that of a newborn rat (Eayrs & Goodhead, 1959;Martin, 1962). Pilkko & Woodbury (1961) obtained results which give only an ascending curvethe mature curve (Fig.…”

Postnatal Changes in Local Cerebral Blood Flow Measured by the Quantitative Autoradiographic [14C]Iodoantipyrine Technique in Freely Moving Rats

“…After weaning time, however, the rat brain is still undergoing quite active maturation that is achieved in this species by 5 to 6 weeks of life after birth (Eayrs, 1964). For example, the cerebral cortex has not attained its full specialization by P21 and the behavior of the rat is still changing after weaning.…”

Effects of Environmental Complexity and Deprivation on Brain Anatomy and Histology: A Review

“…(1964) suggested increased dendritic ramification as one of the factors contributing to the greater EC cortical bulk. They based this hypothesis on a report that postnatal cortical development is largely due to dendritic proliferation (Eayrs & Goodhead, 1959) and that there is a correlation between neuronal perikaryonal size and dendritic branching (Clendinnen & Eayrs, 1961).…”