Effect of hypothyroidism on the size of spines of pyramidal neurons of the cerebral cortex.
We have previously shown that hypothyroidism produces a decrease in the number of spines counted along the apical shafts of pyramidal neurons of the cortex. Nevertheless, other authors have found that when an animal is subjected to some adverse living conditions the size of the spines decreases, making them invisible to the light microscope. The question arises then of whether the decrease in the number of spines reported by us in hypothyroid animals is real or is due to a shrinking effect. In order to elucidate this question the cross-surface area of dendritic spines of apical shafts belonging to 20- and 60-day-old rats, thyroidectomized at 10 days of age, as well as those of their corresponding controls were measured in different layers of their cortex, studied using conventional electron microscopic techniques. The application of the three-way analysis of variance model to these data has shown us that while the age of the animal produces a definite increase in the size of the spines, hypothyroidism does not produce any change in their size, leading us to the conclusion that the decrease in the number of spines previously reported is due to an actual loss of these elements.
D000818:Animals; D002540:Cerebral Cortex / Q000648:ultrastructure*; D003712:Dendrites / Q000648:ultrastructure*; D007037:Hypothyroidism / Q000473:pathology*; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains; D013965:Thyroidectomy