What is the major mechanism through which prion diseases spread in the nervous system?

• A. Neurotransmitter release
• B. Protein aggregation
• C. Direct contact
• D. Excretion into the bloodstream

Answer: (D)

The spread of prion diseases in the nervous system primarily occurs through the mechanism of protein aggregation. Prions are misfolded proteins that can induce other normally folded proteins to also misfold, leading to a chain reaction of aggregation. This protein aggregation contributes to neurodegeneration and is a hallmark of prion diseases such as Creutzfeldt-Jakob disease.

In the context of prion diseases, prions can propagate in neural tissue by converting normal proteins into the pathological form, which then leads to the accumulation of aggregate formations in the brain. This aggregation process facilitates the spread of the disease within the nervous system without the need for traditional vectors like viruses or bacteria, as the infectious agent in prion diseases is a misfolded protein rather than a nucleic acid or an organism.

The other options do not accurately represent the primary mechanism of prion dissemination. Neurotransmitter release pertains to synaptic transmission and communication between neurons but does not involve the propagation of prions. Direct contact refers to the physical transmission of pathogens, which is not how prions spread within the body. Excretion into the bloodstream is not a mechanism of prion spread in the nervous system; instead, prions primarily propagate through direct contact with affected neural tissues.