The Chemistry of Drugs :: Addictions Marijuana Health Science Essays

The Chemistry of Drugs Delta 9 Tetrahydrocannabinol is the primary psychoactive constituent of Cannibis sativa, and is bound to two cannabinoid receptors: CB1 receptors, located primarily in the brain, and CB2 receptors, located primarily in the periphery (Wiley & Martin 2002). A cannabinoid is defined as a substance that has pharmacological properties that resemble those of delta 9 THC i.e. " a drug that binds to CB1 and /or CB2 receptors in vitro and produces a profile of in vivo effects in the tetrad model" (Wiley 2002). THC inhibits the function of the enzyme adenylate cyclase which is involved in the transmission of pain messages. While there are over 60 cannibinoids identified in the plant Cannabis sativa, Delta 9 tetrahydrocannabinol is the primary mood altering psychoactive agent in marijuana. Marijuana effects acetylcholine synthesis and turnover in the limbic region of the brain and in the cerebellum. (Harwood 2005) Eldreth, Matochik Cadet, and Bolla (2004) used PET 15 and a modified version of the Stroop task to determine if 25 day abstinent heavy marijuana users experienced persistent deficits in executive cognitive functioning and brain activity. The performance on a modified version of the Stroop task and brain activity was compared between 25 day abstinent, heavy users, and a matched comparison group. The 25 day abstinent users showed no deficits in performance on the modified version of the Stroop task when compared to the comparison group. They also found that despite the lack of performance differences, the anterior cingulated cortex and the left lateral prefrontal cortex had hyperactivity in the hippocampus bilaterally, when compared to the comparison group. The results suggested that users display persistent metabolic alterations in brain regions responsible for executive cognitive functioning. (Eldreth, Matochik, Cadet, & Bolla 2004). When performing the Stoop task, marijuana users were found to have greater activation compared to the comparison group in the left and right hippocampus. Marijuana users also failed to activate to the same extent as the comparison group in the left lateral prefrontal cortex and the left perigenual anterior cingulated cortex. According to Gardner (2002) drugs that are addictive to humans are similar to animal model systems in five ways. First, drugs enhance electrical brain stimulation reward in the core meso-accumbens reward circuitry of the brain, a circuit encompassing that portion of the medial forebrain bundle which links the ventral tegmental area of the mesencephalic midbrain