12.4: CNS Stimulants: Cocaine, Amphetamines and Cannabinoids

CNS stimulants, such as cocaine, amphetamines, and cannabinoids, have varying structures and mechanisms of action that lead to different therapeutic effects and side effects. Cocaine, with its molecular formula C₁₇H₂₁NO₄, is a tropane alkaloid and a tertiary amino compound. It has two chemical forms: the hydrochloride salt and the "freebase." The former is in powder form, while the latter involves removing the hydrochloride salt to create a form that can be smoked. Cocaine exerts its effects by inhibiting the reuptake of dopamine, serotonin, and norepinephrine into presynaptic neurons, accumulating these neurotransmitters in the synaptic cleft. This results in amplified signaling to post-synaptic neurons. Therapeutically, it's used as a local anesthetic, especially in ophthalmic and other surgical procedures. However, it can cause severe side effects like addiction, cardiovascular diseases, and stroke.

Amphetamine, on the other hand, is an indirect-acting adrenergic agonist. It enhances the release of catecholamines like dopamine and norepinephrine from their storage sites in nerve terminals. The increase in these neurotransmitters leads to heightened alertness, increased concentration, and euphoria. Therapeutically, amphetamines treat attention deficit hyperactivity disorder and narcolepsy. However, they can also cause side effects such as insomnia, reduced appetite, and increased heart rate. Cannabinoids, including Δ⁹-tetrahydrocannabinol (THC), the primary psychoactive compound in marijuana, bind to CB₁ receptors in the brain. THC mimics anandamide, a naturally occurring neurotransmitter, leading to various effects, from relaxation to hallucinations. Synthetic cannabinoids, which are chemically engineered to mimic THC, can be significantly more potent. Therapeutically, cannabinoids can be used for pain relief, to reduce nausea, and to stimulate appetite. However, they can lead to side effects like impaired memory, altered judgment, and addiction. Over time, use can lead to tolerance and dependence. In conclusion, while CNS stimulants can have beneficial therapeutic effects, they also carry risks of significant side effects and must be used under appropriate medical supervision.

CNS stimulants are agents that modulate neuronal activity. These three stimulants each have a distinct structure, mechanism, and effect.

Cocaine, an alkaloid derived from coca plants, increases extraneuronal dopamine concentrations by inhibiting its reuptake.

It enhances alertness, elevates heart rate and blood pressure, and induces euphoria at higher doses.

Prolonged use leads to involuntary motor activity, paranoia, and violence. Cocaine addiction carries risks like cardiac arrhythmias, cerebral vasoconstriction, and seizures, necessitating rehab, psychotherapy, and pharmacotherapy.

Amphetamines, particularly methamphetamine, share similar mechanisms and abuse potential as cocaine. They treat conditions like narcolepsy and ADHD.

Cannabinoids, such as marijuana and its psychoactive alkaloid Δ⁹-THC, act on the brain's CB₁ receptors.

Cannabinoid intoxication impairs cognition and memory. However, Δ⁹-THC has medicinal uses, such as reducing intraocular pressure in glaucoma, inducing muscle relaxation, and possessing antiemetic properties.