Psychopharmacology: Nicotine, Caffeine, Cocaine, and Amphetamines

Vocabulary flashcards covering the pharmacological classifications, mechanisms of action, pharmacokinetics, and toxicological effects of nicotine, caffeine, cocaine, and amphetamines.

Psychostimulants

Drugs that increase activity in the central nervous system, alertness, and energy.

Cocaine

A stimulant that increases dopamine, norepinephrine, and serotonin activity by blocking their reuptake.

Amphetamines

Stimulants that increase monoamine release and reduce reuptake, especially dopamine and norepinephrine.

Monoamines

A class of neurotransmitters that includes dopamine, norepinephrine, and serotonin.

Dopamine transporter (DAT)

A membrane protein that removes dopamine from the synapse and returns it to the presynaptic neuron.

Dopamine reuptake inhibition

Blocking the dopamine transporter (DAT) prevents dopamine from being cleared from the synapse, increasing synaptic dopamine activity.

Cocaine's mechanism of action

Blocks monoamine reuptake transporters, elevating levels of dopamine, norepinephrine, and serotonin in the synaptic cleft.

Amphetamine's mechanism of action

Enters presynaptic neurons, promotes neurotransmitter release from storage vesicles, and reverses transporters to push dopamine out into the synapse.

Synapse

The specialized microscopic junction between neurons across which neurotransmitters diffuse to transmit chemical signals.

Presynaptic neuron

The upstream neuron that synthesizes, packages, and releases neurotransmitters into the synaptic cleft.

Postsynaptic neuron

The downstream neuron that receives neurotransmitter signals via specialized membrane receptors.

Reuptake

The process of transporting released neurotransmitters back across the membrane into the presynaptic terminal via specialized transporter proteins.

Cocaine's local anesthetic effect

Blocks voltage-gated sodium ($\text{Na}^+$) channels along sensory nerve fibers, preventing action potential propagation.

Routes of cocaine administration

Methods such as snorting, injecting, or smoking, which determine how rapidly the drug enters the bloodstream and reaches the brain.

Freebasing

A chemical method that converts powdered cocaine hydrochloride into a purified, smokable freebase form.

Crack cocaine

A smokable, rock-like form of cocaine that produces a rapid, intense, but short-lasting euphoric rush followed by a quick comedown.

Bioavailability

The fraction and rate of an administered drug dose that successfully reaches the systemic circulation in an active state.

Drug onset

The latency or time required following drug administration for initial physiological or psychoactive effects to appear.

Drug duration

The overall time span during which an administered drug continues to produce measurable physiological or behavioral effects.

Cocaine vs. amphetamine duration

Cocaine generally exerts short-lasting effects persisting for $20$ to $80\,\text{minutes}$, whereas amphetamines remain biologically active for $4$ to $12\,\text{hours}$.

Cocaethylene

A toxic metabolite formed in the liver when cocaine and alcohol are consumed concurrently, which has a prolonged half-life and elevated cardiotoxicity.

Methamphetamine

A potent synthetic amphetamine-type stimulant that causes robust dopamine release, rapid central nervous system penetration, and a prolonged duration.

Methamphetamine neurotoxicity

Structural and functional damage to dopaminergic terminal pathways, transporter proteins, and striatal neurons following high or chronic exposure.

Stimulant intoxication

An acute physiological and psychological state marked by elevated energy, alertness, tachycardia, elevated blood pressure, pupillary dilation, and possible agitation.

Stimulant psychosis

A drug-induced psychiatric state that features severe persecutory paranoia, vivid hallucinations, and delusions following high or chronic stimulant use.

Dopamine and psychosis

Excessive dopaminergic neurotransmission, particularly within mesolimbic pathways, is directly linked to psychotic symptoms like paranoia and hallucinations.

Acute stimulant effects

Immediate short-term actions including enhanced vigilance, elevated mood, sympathetic arousal (tachycardia, hypertension), and suppressed appetite.

Chronic stimulant effects

Long-term consequences of repetitive exposure, including sleep disturbances, severe mood dysregulation, dependence, neurotoxicity, and cardiovascular pathology.

Stimulant tolerance

An adaptive state where repeated drug exposure diminishes responsiveness, requiring higher doses to reproduce the original effect.

Sensitization

A neuroadaptive increase in biological or behavioral responsiveness to a drug following repeated intermittent administration.

Tolerance vs. sensitization

A physiological reduction in drug response over repeated exposure versus an augmented, heightened response to the same dose.

Physical dependence

A neurobiological state where the body has adapted to constant drug presence and experiences characteristic withdrawal symptoms upon cessation.

Psychological dependence

A strong cognitive craving, emotional compulsion, or perceived necessity to repeatedly consume a drug to function or maintain well-being.

Stimulant withdrawal

An abstinence syndrome featuring intense physical fatigue, hypersomnia, depressed mood, anhedonia, and increased appetite.

Stimulant crash

An acute period of exhaustion, profound lethargy, and dysphoria that occurs as high stimulant concentrations abruptly leave the body.

Compensatory responses

Physiological adaptations produced by the body to oppose drug actions and maintain internal homeostasis.

Reward pathway

A neural circuit involving dopaminergic projections from the ventral tegmental area to the nucleus accumbens that drives reinforcement, motivation, and reward.

Drug reinforcement

The pharmacological property of a substance that strengthens the behaviors associated with taking it, thereby increasing the probability of future use.

Drug craving

A powerful, obsessive urge or perceived psychological need to acquire and consume a specific substance.

Stimulant addiction

A chronic, relapsing disorder involving compulsive substance seeking and use despite severe adverse physical, psychological, and social consequences.

Caffeine

A widely consumed central nervous system stimulant that promotes wakefulness and alertness primarily by blocking adenosine receptors.

Methylxanthines

A chemical family of plant-derived alkaloid stimulants that includes caffeine, theophylline, and theobromine.

Adenosine

An endogenous inhibitory neuromodulator that promotes sleepiness, sedation, and vasodilation by dampening central nervous system activity.

Adenosine receptors

Cell-surface purinergic receptors that mediate sleep-inducing signaling, which caffeine competitively binds and blocks to prevent sedation.

Caffeine's mechanism of action

Direct competitive antagonism at adenosine receptors, which prevents endogenous adenosine from binding, thereby reducing drowsiness and promoting alertness.

Adenosine A1 receptors

Inhibitory purinergic receptors distributed throughout the brain that suppress neurotransmitter release and promote sleepiness.

Adenosine A2A receptors

Purinergic receptors located in striatal and dopamine-rich regions that regulate sleep homeostatic pressure and interact with dopamine transmission.

Caffeine and dopamine

By blocking adenosine $A_{2\text{A}}$ receptors, caffeine removes tonic inhibition from dopamine receptors, indirectly enhancing dopaminergic signaling.

Caffeine absorption

Rapid and complete gastrointestinal uptake following oral consumption, usually reaching systemic circulation within $30$ to $60\,\text{minutes}$.

Caffeine distribution

Equal dispersal throughout total body water, allowing it to readily cross both the blood-brain barrier and the placental barrier.

Blood-brain barrier

A selective endothelial boundary with tight junctions that protects cerebral tissue by regulating the entry of substances from the bloodstream.

Caffeine metabolism

Hepatic biotransformation of caffeine into downstream metabolites (paraxanthine, theobromine, theophylline) predominantly performed by CYP1A2.

CYP1A2

The principal cytochrome P450 liver enzyme responsible for metabolizing approximately $95\%$ of ingested caffeine.

Caffeine half-life

The duration needed for the human body to eliminate half of the circulating caffeine, typically spanning $3$ to $7\,\text{hours}$ in healthy adults.

Factors affecting caffeine metabolism

Physiological and external variables including pregnancy, liver disease, oral contraceptives, genetics, and tobacco use that alter metabolic speed.

Smoking and caffeine metabolism

Chemical hydrocarbons produced during cigarette smoke combustion induce CYP1A2 enzymes, speeding up caffeine breakdown by roughly $50\%$.

Smoking cessation and caffeine

Quitting smoking causes liver enzyme induction to subside, which slows caffeine clearance and can amplify caffeine's effects if intake is unchanged.

Caffeine tolerance

A reduction in sensitivity to caffeine's cardiovascular, blood pressure, and sleep-disrupting actions after repeated daily consumption.

Caffeine dependence

A state of neuroadaptation resulting from habitual caffeine consumption that produces withdrawal symptoms when intake is stopped.

Caffeine withdrawal

An abstinence syndrome featuring prominent headaches, daytime fatigue, irritability, difficulty concentrating, and depressed mood.

Caffeine withdrawal headache

Cephalalgia caused by rebound cerebral vasodilation when the vasoconstrictive effects of caffeine wear off, allowing adenosine to dilate blood vessels.

Caffeine withdrawal timeline

Symptoms typically emerge within $12$ to $24\,\text{hours}$, peak at $24$ to $48\,\text{hours}$, and resolve within approximately one week.

Caffeine intoxication

An acute syndrome resulting from excessive consumption marked by restlessness, psychomotor agitation, insomnia, muscle twitches, and tachycardia.

Caffeinism

A chronic clinical pattern of severe caffeine overuse characterized by chronic anxiety, irritability, persistent insomnia, tremors, and cardiac arrhythmias.

Caffeine and sleep

By opposing adenosine somnogenic signaling, it reduces drowsiness, extends sleep onset latency, and shortens deep restorative sleep.

Caffeine and memory

Promotes vigilance and sustained attention, which can indirectly aid memory performance and improve post-learning memory consolidation.

Caffeine and attention

Produces temporary enhancements in psychomotor vigilance, reaction time, and sustained concentration during fatiguing tasks.

Caffeine and physical performance

Exerts ergogenic actions by decreasing perceived physical exertion, delaying exhaustion, and improving aerobic endurance.

Energy drinks

Canned beverages containing high doses of caffeine alongside additives like taurine, B-vitamins, and herbal extracts marketed to boost stamina.

Caffeine and alcohol

Masks subjective perceptions of drowsiness and drunkenness without reducing alcohol's objective motor discoordination or cognitive deficits.

Caffeine and pregnancy

Freely diffuses across the placenta to the fetus, while maternal clearance slows substantially, extending the drug's circulation time.

Caffeine and breastfeeding

Passes into breast milk in small amounts, where high maternal intake can lead to infant irritability, fussiness, and poor sleep.

Caffeine and cardiovascular effects

Can cause acute, transient elevations in peripheral blood pressure, vascular resistance, and cardiac contractions in sensitive individuals.

Caffeine overdose

Severe, life-threatening toxicity from massive doses that can trigger ventricular arrhythmias, metabolic acidosis, and generalized seizures.

Caffeine and bone health

High intake can slightly impair intestinal calcium absorption and increase excretion, potentially lowering bone density if calcium intake is inadequate.

Nicotine

A potent, highly addictive stimulant alkaloid that occurs naturally within plants of the tobacco genus.

Nicotiana tabacum

The large-leaf cultivated tobacco plant species widely grown and processed for commercial cigarettes, cigars, and smokeless tobacco.

Nicotiana rustica

A small-leaf tobacco variety known for bitter smoke and exceptionally high nicotine concentration, used largely for ceremonial purposes.

Nicotinic acetylcholine receptors (nAChRs)

Ligand-gated ion channels located across the central and peripheral nervous systems that are selectively opened by acetylcholine and nicotine.

Acetylcholine

An endogenous neurotransmitter vital for muscle contraction, autonomic functioning, attention, arousal, and memory processes.

Nicotine's mechanism of action

Directly binds and activates nicotinic acetylcholine receptors, opening an internal ion channel to depolarize the neuron.

Ionotropic receptors

Membrane receptors that contain an integral ion channel, opening directly upon ligand binding to produce rapid, millisecond-scale electrical flux.

Metabotropic receptors

G-protein-coupled receptors that activate intracellular enzymatic signaling cascades rather than directly conducting ions.

Nicotinic vs. muscarinic receptors

Two acetylcholine receptor types: one consists of fast ligand-gated ion channels, whereas the other consists of slower metabotropic G-protein pathways.

nAChR structure

A pentameric macromolecular protein arrangement composed of five individual subunits encircling a central pore.

Nicotinic receptor subunits

Various combinations of alpha ($\alpha$) and beta ($\beta$) proteins whose arrangements determine binding affinity, location, and desensitization rate.

Depolarization

A positive change in a neuron's electrical membrane potential that drives it closer to the threshold for triggering an action potential.

Nicotine and ion movement

Receptor gating permits the rapid influx of positively charged sodium ($\text{Na}^+$) and calcium ($\text{Ca}^{2+}$) ions, causing cellular excitation.

Nicotine and neurotransmitter release

Stimulation of presynaptic and postsynaptic nicotinic receptors triggers the release of multiple chemical messengers, notably dopamine and glutamate.

Nicotine and dopamine

Increases dopamine release within mesolimbic reward structures, producing reinforcing sensations that drive persistent tobacco use.

Nicotine reward pathway

Activation of the ventral tegmental area and nucleus accumbens, reinforcing drug administration and underpinning dependence.

Nicotine absorption

Uptake into circulation across various mucosal and barrier surfaces including the lungs, buccal cavity, nasal passages, skin, and GI tract.

Pulmonary absorption

Rapid uptake of aerosolized or vaporized drug across the expansive capillary beds of the lung alveoli directly into arterial blood.

Nicotine delivery speed

Inhaled nicotine reaches cerebral tissue in approximately $7\,\text{seconds}$, traveling faster than intravenous arm injections which take about $14\,\text{seconds}$.

Nicotine from cigarettes

Delivery achieved via tobacco combustion, generating an acidic smoke that allows rapid, efficient pulmonary alveolar absorption.

Nicotine from vaping

Delivery achieved by electrically heating an e-liquid solution to create an inhalable aerosol that deposits nicotine into the lungs.

Nicotine from smokeless tobacco

Slower transmucosal absorption occurring through the membranes lining the cheeks and gums without involving inhalation.

Nicotine metabolism

Primary biotransformation occurring in the liver, where roughly $80\%$ of circulating nicotine is enzymatically converted to cotinine.

CYP2A6

The specific cytochrome P450 hepatic enzyme responsible for the majority of nicotine clearance and its conversion to cotinine.

Cotinine

The primary inactive metabolite of nicotine, which exhibits a much longer half-life and serves as the clinical biomarker for tobacco exposure.