**Question:** Negri bodies are located in -

A. Motor neurons
B. Sensory neurons
C. Astrocytes
D. Ependymal cells

**Correct Answer:** D. Ependymal cells

**Core Concept:** Negri bodies are intracytoplasmic inclusions that are characteristic of rabies virus infection. They are formed due to the accumulation of viral proteins within infected cells.

**Why the Correct Answer is Right:** Negri bodies are found in the cytoplasm of ependymal cells, which are specialized cells that line the ventricles of the brain and the spinal cord. In the context of rabies virus infection, these bodies represent the site of viral replication and provide evidence of the disease.

**Why Each Wrong Option is Incorrect:**

A. Motor neurons: Negri bodies are not found in motor neurons, as they are not the primary site of viral replication.
B. Sensory neurons: Similarly, sensory neurons are not the primary site of viral replication, and therefore Negri bodies are not found in them.
C. Astrocytes: Astrocytes are involved in supporting and maintaining the blood-brain barrier, but they are not the primary site of viral replication.

**Clinical Pearl:** The presence of Negri bodies in ependymal cells is a key diagnostic feature of rabies virus infection, particularly in brain tissue examination during post-mortem studies. This helps differentiate rabies from other encephalitis cases.

**Explanation:**

Negri bodies are specific to the rabies virus infection, and their presence helps in diagnosing rabies. In the context of rabies, these bodies are formed due to the accumulation of viral proteins within the infected cells. The correct answer, D, refers to ependymal cells, which are specialized cells that line the ventricles of the brain and the spinal cord. These cells are the primary site of viral replication in rabies, leading to the formation of Negri bodies.

In contrast, option A refers to motor neurons, which are not the primary site of viral replication in rabies. Similarly, sensory neurons (option B) and astrocytes (option C) are not the primary sites of viral replication, as they are not involved in supporting the blood-brain barrier as ependymal cells are.

The presence of Negri bodies in ependymal cells is a key diagnostic feature of rabies virus infection, particularly in brain tissue examination during post-mortem studies. This feature helps differentiate rabies from other encephalitis cases.