The Effects of a Neurotoxin on the Mammalian Brain

Paper Summary:

The paper shows that in the study of structural development in the brain there have been several proposed biomarkers for quantifying brain plasticity. These include but are not limited to cortical thickness, dendritic length and branching, expression of neuronal proteins, and the presence of DNA adducts. The paper discusses the theory that a measure of brain plasticity emerging late in embryonic development will be a very sensitive biomarker for detecting subtle damage suffered by brain cells during earlier stages of brain development not detectable by other means. The paper shows that to test this, the effects of a neurotoxin on the late developing dendritic spines were studied. A significant decrease in spine density was observed as the neurotoxin, methylazoxymethanol, increased. The author of the paper shows how the implications are widespread in the study of neuro-degenerative disease.

From the Paper:

"Fifty years ago, Donald Hebb demonstrated that the conditions under which laboratory rats were housed could significantly affect their performance in a variety of complex spatial tasks later in life (1). The complex environment rearing paradigm has been valuable in assessing plasticity of a variety of brain components including cerebral cortical microvasculature, astrocyetic morphology, dentritic branching patterns, synaptic number, and synaptic structure are all affected by complex environment rearing (2). It has been suggested that multiple synaptic contacts (spines) may play a role in the spread of the additive effect of learning known as potentiation, among neighboring unstimulated neurons. A lack of these spines and their connection with boutons of neighboring neurons could then result in a decrease in the capacity for learning. Some recent work has indicated that the presence of multiple synaptic contacts may be altered by experience. Most of this research has focused on structural changes in the hippocampus. Dendrtic spines show great variability in structure and connectivity, both within and across brain structures, including 10-fold differences in length and diameter as well as variations in the number of branches and spines per dendrite."

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