First some background: The spinal cord is a bundle of nerve axons that descend from the brain down the back, to around the area of the waist. It is responsible for delivering and relaying messages traveling to and from the brain. The spinal cord is surrounded by bones known as vertebrae, which function to protect the spinal cord from damage or injury. However, it is still possible for damage to occur as a result of severe trauma, which tends to affect bodily functions below the area of injury. However, the initial trauma is not usually the major cause of cell death in the spinal cord. Necrosis occurs after a nerve cell axon is compressed, leading to swelling and eventually bursting. Additionally, a different process occurs known as apoptosis, or programmed cell death, in which neurons surrounding the initial area of damage receive a signal to essentially kill themselves. In spinal cord injuries this normally occurs in two waves: one wave eight hours after the initial injury that affects a specific cell type known as glial cells. The second wave occurs about seven days later in a different cell type known as oligodendrocytes, which can occur at areas distant from the epicenter of injury. This exacerbates initial damage and leads to increased loss of bodily functions.
The new information: It was found that by activating cannabinoid CB1 and CB2 receptors, neuronal axons were preserved at the immediate region of injury. Axons are long extensions of brain cells that form the actual spinal cord. These axons, also known as white matter, are coated with a fatty insulating material known as the myelin sheath, which is formed in the periphery by oligodendrocytes. It was shown that by activating these cannabinoid receptors, there was preservation of white matter and a decreased level of oligodendrocyte death at the epicenter. Additionally, the cannabinoid also inhibited myelin damage and oligodendrocyte loss at areas distant from the injury epicenter due to delayed apoptosis.
What this means: Currently, there are only two possible treatments for spinal cord injury that may help to halt the progression of neuronal damage: anti-inflammatory medication, and cold saline. Both of these work by decreasing the amount of signals that can be received by the cell processes in the spinal cord. However, anti-inflammatory medications may lead to an increased risk of infection, and administration of cold saline lacks empirical evidence to prove its effectiveness. This experiment showed that cannabis can possibly be used immediately following acute spinal cord injuries to decrease the amount of damage, and thus decrease the loss of function in patients.
Arevalo-Martin, A., et al. “The endocannabinoid 2-arachidonoylglycerol reduces lesion expansion and white matter damage after spinal cord injury.” Neurobiology of Disease. (2010): preprint.