Lecture 15 Cannabinoids and Nicotine Final Test

What is a "cannabinoid" and what does its chemical structure look like?

A class of lipophilic, multi-ringed hydrocarbon molecules that bind to cannabinoid receptors. Unlike alkaloids, their chemical backbones completely lack nitrogen atoms.

How does the chemical structure of nicotine compare to a cannabinoid?

Nicotine is a small, water- and fat-soluble alkaloid consisting of a pyridine ring attached to a pyrrolidine ring. Crucially, it contains nitrogen atoms, which cannabinoids lack entirely.

What does the term "psychotropic" mean?

Any chemical substance that readily crosses the blood-brain barrier to act primarily on the central nervous system, altering brain function, perception, mood, or behavior.

What are the 3 major psychotropic constituents found in cannabis?

1. Delta-9-Tetrahydrocannabinol (Delta-9-THC)\n2. Cannabidiol (CBD)\n3. Cannabinol (CBN)

Where is THC content most heavily concentrated in the cannabis plant?

In the sticky resin secreted by the glandular trichomes (hairs) located primarily on the flowering tops (buds) and adjacent small leaves of the female plant.

How does smoking different parts of the cannabis plant affect the subjective experience?

Smoking the flowering tops (buds) delivers a highly concentrated payload of THC, creating a rapid, steep spike in brain concentration that maximizes the magnitude of subjective effects and reinforcement value compared to smoking low-THC fan leaves.

What are the cellular, intracellular effects of stimulating CB1 and CB2 receptors?

Both are Gi/o-protein-coupled receptors. Stimulating them inhibits adenylyl cyclase (lowering cAMP), inhibits voltage-gated calcium channels, and opens inward-rectifying potassium channels.

What are 2 precise ways that retrograde endocannabinoids inhibit presynaptic neurotransmitter release?

1. They block presynaptic calcium influx, preventing neurotransmitter vesicles from fusing with the membrane.\n2. They open presynaptic potassium channels, hyperpolarizing the terminal axon so incoming action potentials cannot trigger release.

Describe the structure and channel type of the nicotinic acetylcholine receptor (nAChR).

It is a pentameric (5-subunit), ionotropic ligand-gated cation channel that permits the influx of sodium (Na+) and calcium (Ca2+) upon activation.

Which specific nAChR subunit composition mediates nicotine's primary reinforcing properties, and where is it located?

The alpha-4-beta-2 (a4b2) subunit configuration, which is localized with high affinity on dopamine cell bodies within the Ventral Tegmental Area (VTA).

What is the general biological mechanism responsible for short-term nicotine tolerance?

Rapid receptor desensitization. Upon binding nicotine, the nAChR quickly enters a closed, refractory state where it temporarily refuses to open again, even if nicotine is still present.

What is the general biological mechanism responsible for long-term nicotine tolerance?

A compensatory up-regulation of nAChR expression. Because chronic smoking constantly desensitizes and shuts receptors off, the brain compensates by packing significantly more nAChR proteins into the synaptic membranes.

How do "chippers" differ from dependent tobacco users regarding drug intake and withdrawal?

Chippers smoke regularly but lightly (5 or fewer cigarettes/day), showing an absolute absence of intake escalation, no functional dependence, and zero somatic withdrawal signs upon abstinence.

Describe the behavioral and clinical profile of a "moderately dependent" nicotine user.

They smoke half a pack to a pack a day. They display clear, uncomfortable withdrawal signs (irritability, anxiety, cravings) if forced to go hours without smoking and actively modify their schedules to maintain access.

Describe the behavioral and clinical profile of a "strongly dependent" nicotine user.

They smoke more than a pack a day, often lighting up within 5 minutes of waking. They exhibit massive physical tolerance, experience profound somatic withdrawal rapidly, and will continue smoking even during severe physical illness.

What characterizes Type 1 marijuana dependence?

Daily, high-frequency heavy use. The user exhibits high pharmacodynamic tolerance, severe psychological cravings, and a clear functional somatic withdrawal syndrome (insomnia, irritability, loss of appetite) upon cessation.

What characterizes Type 2 marijuana dependence?

Intermittent, situational, or lower-frequency use. Physical tolerance and somatic withdrawal are low or absent, but the user displays a strong psychological reliance on the drug to cope with stress, social settings, or negative affect.

Contrast the subjective effects of Nicotine vs. THC.

Nicotine acts as a psychomotor stimulant inducing alert energy, cognitive focus, and concurrent relaxation. THC induces relaxation, mild euphoria, altered sensory perceptions, heightened appetite, and short-term memory deficits.

Contrast the animal and human withdrawal signs of Nicotine vs. THC.

Nicotine withdrawal causes severe irritability, anxiety, and weight gain in humans, and gasps/shakes in animals. THC withdrawal causes insomnia, vivid dreams, and mild nausea in humans, and can be unmasked in animals via precipitated CB1 antagonists.

Contrast the half-lives of Nicotine vs. THC.

Nicotine has a very short elimination half-life of approximately 2 hours. THC has a long, prolonged half-life of 20 to 30+ hours due to extensive accumulation and slow leaching out of body fat tissues.

Contrast the metabolism of Nicotine vs. THC regarding active metabolites.

Nicotine is metabolized into cotinine, which is largely inactive. THC is metabolized into 11-hydroxy-THC, which is a highly potent, fully active agonist that strongly drives the drug's ongoing psychological effects.

Contrast the baseline mechanism of action between Nicotine vs. THC.

Nicotine is a direct full agonist at ionotropic nicotinic acetylcholine receptors (nAChRs). THC is a partial-to-full agonist at metabotropic, Gi/o-protein-coupled cannabinoid (CB1 and CB2) receptors.

How does nicotine's 2-hour half-life directly explain the typical daily smoking pattern of regular users?

Because blood levels drop drastically every 2 hours, dependent smokers must repeatedly dose themselves at frequent, regular intervals throughout the day (approx. every 1-2 hours, or one pack a day) to prevent early withdrawal distress.

What is the timeline for peak high and duration when nicotine or THC are inhaled (smoked/vaped)?

Inhalation yields a rapid peak effect within 3 to 10 minutes due to instant alveolar absorption, but a short duration of action (dropping within 1 to 2 hours) as the drug redistributes away from the brain.

What is the timeline for peak high and duration when nicotine or THC are orally ingested?

Oral ingestion delays the peak high for 1 to 3 hours due to slow gastric transit and first-pass liver metabolism, but provides a prolonged, steady duration of action lasting 4 to 8+ hours.

How does cannabis compare to alcohol and cocaine regarding clinical indicators of addiction liability?

Cannabis tracks lower across reinforcement strength, relapse rates, and withdrawal severity. Cocaine has vastly higher immediate reinforcement, and alcohol withdrawal unmasks life-threatening somatic crises (seizures/DTs) that cannabis does not produce.

What is the core pharmacokinetic stabilization principle of substitution therapies?

They provide a controlled, slower-acting formulation with a long half-life to keep target receptors safely occupied. This staves off severe withdrawal, eliminates the behavioral 'high/crash' cycle, and blocks the reinforcement of a relapse.

List the current major substitution therapies utilized for Tobacco Use Disorder.

Nicotine Replacement Therapies (NRTs), including transdermal nicotine patches, nicotine gums, lozenges, inhalers, and nasal sprays.

Why are current cannabinoid-related therapies (like Dronabinol/synthetic THC) suitable as substitution choices for Cannabis Use Disorder?

They safely bind to and stabilize central CB1 receptors, blunting withdrawal symptoms like severe insomnia, irritability, and anorexia during detox without the high-potency spikes of smoked cannabis.

What is the pharmacological rationale behind using Varenicline (Chantix) for Tobacco Use Disorder?

It is a partial agonist at alpha-4-beta-2 nicotinic receptors. It releases enough baseline dopamine to stop withdrawal cravings while simultaneously blocking any smoked nicotine from binding if the user relapses.

What is the pharmacological rationale behind using Bupropion (Wellbutrin/Zyban) for Tobacco Use Disorder?

It is a norepinephrine-dopamine reuptake inhibitor (NDRI). By boosting baseline dopamine and norepinephrine independent of nicotine, it props up the brain's missing reward signaling to alleviate withdrawal depression and low energy.

What is the clinical rationale behind using FAAH inhibitors to treat Cannabis Use Disorder?

FAAH is the enzyme that breaks down your body's natural endocannabinoid, anandamide. Inhibiting FAAH allows native anandamide levels to rise and gently stabilize withdrawal-weakened CB1 receptors without introducing an intoxicating foreign agonist.