CANNABINOID RECEPTORS
Delta-9 tetrahydrocannibinol (THC) is a cannabinoid that mimics the body’s natural “ligand” anandamide. THC is unique, it is not a sedative nor a psychedelic, it employs particular methods of action. Cannabinoid receptors inhibit calcium ion flux and open potassium channels, they are made up of a chain of 473 amino acids which contains 7 hydrophobic columns. These hydrophobic cylindrical columns continue throughout the cell membrane. THC binds by connecting to the outside or the extracellular portion of the receptor, the receptor deploys a second messenger G-protein. A G-protein cyclical nucleotide second messenger system activates and inhibits adenylate cyclase. After going through several processes THC eventually moderates the potassium and calcium ion channels and cyclical AMP (Julien, 1997) (Joy, Watson & Benson, 1999).
Cannabiniod receptors have been found in invertebrates such as mollusks and leaches. Cannabinoid receptors are one of the most numerously occurring G-protein linking receptors in the brain. Their high prevalence in the human brain and body, and the fact that a largely differential number of species contain them is a possible demonstration of their importance to function. It is thought cannabinoid receptors have had a long evolutionary history (Joy, Watson & Benson, 1999).
Large numbers of cannabinoid receptors are found in the frontal cortex as well as other cortical areas. The frontal cortex is responsible for the effects of the high experienced by marijuana smokers. This moderates in general higher cognitive processes. Sensory cortical areas near the central gyrus are responsible for other cognitive and perceptual distortions. The processing abilities of the cortex in general are distorted in terms of sound, concentration, reality, time, color and taste by the exercise smoking or using of marijuana (Julien, 1997).
The cerebellum and the basal ganglia which deal with overall spatial coordination contain some of the densest areas of cannabinoid receptors in the brain as a whole. Movement and postural control are affected by smoking marijuana. Deficits in psychomotor coordination have been well documented in many studies summarized in (Julien, 1997).
Cannabinoid receptors are also prevalent in the hippocampal region of the brain. The hippocampus is responsible for cognitive processing and abilities in many learning and memory tasks. The high frequency of cannabinoid receptors could very well be responsible for the disruption of memory processes affected by THC. THC promotes deficits in the encoding of memories and storage and retrieval. Anandamide the body’s natural ligand has been shown to play a similar role to that of THC in hippocampal functioning. It regulates synaptic plasticity which relates to memory and also learning. This is one main point of evidence as to why Anandamide is considered a natural cannabinoid (Julien, 1997).