Investigators:
- Robert E. Akins, PhD
- Mary C. Theroux, MD
- Freeman Miller, MD
- Kirk W. Dabney, MD
Background
This study is part of a larger research effort to understand the pathophysiology of nerve-muscle interactions in children with neurologic injuries and diseases. Overall, we are interested in studying the structural and functional perturbations that may occur at neuromuscular junctions (NMJs) as a result of neurologic insult or deficit. In this study we look at NMJs in children with cerebral palsy (CP). We think that children with CP may have intrinsic abnormalities in their neuromuscular junctions, and we are attempting to understand the extent and nature of this pathophysiology by studying aspects of the structure and function of neuromuscular junctions.
Cerebral Palsy
Studies show that, in recent years, the prevalence of cerebral palsy is on the rise, and CP is the most common neurologic condition in children. It is a disorder of the central nervous system in which an insult sustained in fetal or early neonatal life results in spasticity and motor dysfunction. The effects on the motor system, clinically, are similar to those seen in the adult disease states of stroke, closed-head injury, encephalitis, and spinal cord injury. Despite the similarities in motor dysfunction seen in CP and other neurological conditions, few investigations have been conducted to examine the nerve-muscle interactions in children with CP, so we are establishing a research program to begin studying these interactions.
Neuromuscular Junctions
The surface of skeletal muscle contains proteins called acetylcholine receptors (AChRs). In the normal state, AChRs are confined to the area on the muscle that is contacted by a nerve. This area is called the neuromuscular junction. When a person wishes to contract a muscle, the nerve fires, and a small amount of a chemical messenger called acetylcholine is deposited at the neuromuscular junction. The AChR "sees" this chemical and induces the muscle to contract. Another protein at the neuromuscular junction, called acetylcholine esterase, chops up the chemical messenger so that there is none left at the junction. Normally, these two proteins are found together and only at neuromuscular junctions. Neurological diseases in adults that cause spasticity, such as stroke, closed head injury, encephalitis and spinal cord injury, all lead to abnormal neuromuscular junctions that are characterized by the appearance of AChRs away from their normal localization, and we think that this may be true in children with CP as well.
What We're Doing
Children with cerebral palsy (CP) undergo a large number of surgical procedures, and, after getting the permission of the childs parent, we are using small pieces of muscle that are collected during scheduled surgeries. We use a method to stain these pieces of muscle so that we can see where the acetylcholine receptor and the acetylcholine esterase proteins are located. The first thing we did was to compare the staining patterns found in muscle taken from children with CP to those found in children without CP to see if there were differences.
Some of What We've Found
In children undergoing surgeries to correct scoliosis, we have found that those who do not have cerebral palsy (CP) have neuromuscular junctions in which the acetylcholine receptor (AChRs) and acetylcholine esterase (AChEase) proteins localize in the same spots. The photograph shown above is an example of what we see. The top three panels show low power images taken through a specialized microscope. Red indicates where the AChR is located, green shows where the AChEase is located. By combining both images, we can see if there are areas where the AChR occurs without the AChEase. The two lower sets of images give examples of normal and abnormal staining. In children with CP, a significant subset of children have abnormal staining patterns and non-junctional AChRs.