Cord Mishaps
When transmissions from the peripheral tissues (such as muscles) arrive at the entrance to your spinal cord, they synapse with a second set of neurons. As you read in the section on Neurons Switching Function, these neurons have NMDA receptors on them. In fibromyalgia patients, the NMDAs are amplifying incoming signals and leading to a reduced pain threshold.
The second set of neurons can send the signal up to the brainstem, a control center at the top of the cord, and eventually it may reach your brain. But not all messages reach these higher centers because of the Bottom-Up and Top-Down control systems. The main control hub for the Top-Down system is in the brainstem, the mid-level player that will be addressed in the next article.
Focusing on the Bottom-Up controls, they operate primarily within the cord by employing a massive community of spinal interneurons (like tiny jumper cables). There are two main types: those that release GABA or opioids to inhibit signals and those that release glutamate to increase signals. Remember, glutamate charges up the NMDAs.
Ordinarily, nuisance signals are filtered out by GABA, and to a lesser extent, by opioids. Urgent messages get amplified by glutamate. Due to the high glutamate levels and the activation of the NMDAs, your Bottom-Up system tends to enhance the signals traveling up the cord.
Aside from modulating incoming signals entering the cord, spinal interneurons play an essential role in locomotion. They connect the left and right sides of your body to coordinate movement. Given the GABA/glutamate imbalances, the interneurons could be contributing to your balance and coordination difficulties.
Medications that increase GABA may help the Bottom-Up controls work better, but they are limited by their sedating side effects. Memantine is a drug that blocks glutamate, but it also causes sleepiness.
Nondrug alternatives are another option and without the side effects. One study shows reducing dietary glutamate, such as MSG and similar flavor-enriching agents used in processed foods, reduces fibromyalgia symptoms. See the section on Diet & Nutrition for details about the study and how you can follow this dietary protocol. Acupuncture also decreases CNS glutamate in people with fibromyalgia … if you can afford it.