Marijuana

Mode of Action: 

Marijuana, or cannabis, contains a psychoactive chemical from the cannabis plant. 

Receptors of the THC molecule are found in various regions of the brain which include the hyppocampus and the cerebellum.

The absence of areas such as the medulla, which controls vital function, accounts for the fact that even when taken in large doses it's not lethal.

The attachment of THC to receptors in different parts of the brain can account for the various effects of cannabis:

• Cerebellum: movement and posture. producing tendency to sit still.

• Frontal cortex: affects cognitive processing. Creates sensory distortions and affecting concentration.

• Hippocampus: disruption of memory.

When cannabinois attach to their receptors on the pre-synaptic membranes of neurones, they inhibit the release of other neurotransmitters. Applies to both THC and natural cannabinoids, such as anandamide.

ledent et al. (1999) used knockout mice which lacked the gene to produce the cannabinoid receptor. These mice did not respon to cannbinoid drugs, confirming the association between the resptors and the action of THC. 

Effects of Marijuana:

Medically, cannabis produces effects such as:

• analgesia

• sedation

• appetite stimulation

• reduction of pressure in the eye.

However, cannabis also interferes with attention and perception, mood, movement, learning and memory.

Similar short-term effects of cannabis on memory are seen in humans as have been found in animals. 

Kurzthaler et al. (1999) used a double-blind design…