Mechanical Impacts to the Skulls of Rats Produce Specific Deficits in Maze Performance and Weight Loss: Evidence for Apoptosis of Cortical Neurons and Implications for Clinical Neuropsychology

Abstract

The purpose of this experiment was to induce closed head injuries that might be applicable to clinical neuropsychology. Six adult female albino rats were struck over the right dorsal skull by a 200-gm weight that fell through a 0.9-m tube while another six rats served as controls. The rats that received the impact to the skulls displayed significantly more weight loss and fewer completions of the maze during the subsequent two to four days (effect size about 40%) while their open field behaviors, response latencies to thermal stimulation of the feet, and immobility within a conditioned fear setting did not differ significantly from those of controls. Histological analyses of the brains about 35 days after the impact indicated striking alterations in the morphology of cerebral cortical neurons, strongly suggestive of an apoptotic-like process, within the dorsal cerebral cortices below the likely impact site. Distributions of clusters of these aberrant-looking cells were also evident opposite to the impact site within the ventral cerebrum. Because apoptosis is involved with minimal inflammation and edema, detection of diffuse apoptosis by MRI and CT would be unlikely even though the influence on adaptability would be significant.