Hypnotics, Sleep Architecture, Anticonvulsants, and Antiparkinsonian Agents

Vocabulary practice flashcards focusing on the pharmacology of hypnotics, sleep architecture, antiepileptics, antiparkinsonian agents, and antispasticity drugs.

Hypnotics

Drugs that facilitate falling asleep and increase the depth and duration of sleep, primarily indicated for sleep disorders like insomnia and sleeplessness.

Sleep

A genetically determined condition of homoitherms (warm-blooded animals) characterized by regular, sequential polygraph patterns organized into cycles, phases, and stages, regulated by the hypnogenic brain stem system and biological rhythms.

Polysomnography

A diagnostic assessment combining simultaneous electroencephalography (EEG), electrooculography, electromyography, and the monitoring of vegetative functions to assess sleep architecture.

Stage 0 Sleep (Awake)

The transitional state from lying down to sleep onset including occasional nocturnal awakenings ($1\text{--}2\%$ of sleep time), showing $\alpha$ waves with closed eyes, $\beta$ waves with open eyes, and irregular or rolling eye movements.

Stage 1 Sleep (Dozing)

An initial light sleep stage ($3\text{--}6\%$ of sleep time) characterized by the appearance of $\alpha$ and $\theta$ waves, rolling eye movements, neck muscle relaxation, and easy arousal by external stimulation.

Stage 2 Sleep (Unequivocal Sleep)

A sleep stage ($40\text{--}50\%$ of total sleep) characterized on EEG by $\theta$ waves with interspersed sleep spindles (linked to information consolidation) and sensory-evoked K-complexes.

Stage 3 Sleep (Deep Sleep Transition)

A transitional deep sleep stage ($5\text{--}8\%$ of total sleep) exhibiting $\theta$, $\delta$, and spindle activity, where K-complexes require strong stimuli to evoke and arousal is difficult.

Stage 4 Sleep (Cerebral Sleep)

The deepest sleep stage ($10\text{--}20\%$ of total sleep) where $\delta$ waves predominate, K-complexes cannot be evoked, eyes remain practically fixed, awakening is difficult, and night terrors can occur.

Slow (NREM) Sleep

Also called forebrain or slow-wave sleep; regulated by the thalamus, dorsal raphe nuclei, and $\delta$-sleep peptide, characterized by synchronized EEG, muscle relaxation, lower blood pressure, and restorative anabolic activity.

Fast (REM) Sleep

Paradoxical or afterbrain sleep regulated by pontine reticular structures (locus coeruleus, giant-cell nucleus); characterized by desynchronized saw-shape EEG, rapid eye movements, dreaming, sympathetic activation, and profound skeletal muscle atonia.

Ascending Arousal System

A wakefulness-maintaining dual-pathway system consisting of a cholinergic branch (pedunculopontine and laterodorsal tegmental nuclei to thalamus) and a monoaminergic branch releasing histamine, norepinephrine, and serotonin.

Sleep Switch

A bidirectional inhibitory circuit between sleep-promoting GABAergic neurons of the ventrolateral preoptic nucleus and wake-promoting monoaminergic nuclei, stabilized by hypocretin (orexin).

Narcolepsy with Cataplexy

A neurological condition caused by deficient hypocretin (orexin) levels, impairing sleep switch stability and causing erratic transitions between sleep and wakefulness.

Presomnia

A disorder of sleep initiation characterized by difficulty falling asleep, common in young and middle-aged individuals experiencing daytime stress.

Intrasomnia

A sleep disorder characterized by superficial sleep and frequent nocturnal awakenings, commonly associated with somatic or psychoneurotic disorders.

Postsomnia

A sleep disorder manifested by abbreviated total sleep time and early morning awakening, commonly observed in elderly individuals due to age-related CNS changes.

$\text{GABA}_A$ Receptor Complex

A pentameric ligand-gated ion channel composed of $2\alpha$, $2\beta$, and $\gamma$ subunits that mediates neuronal hyperpolarization via chloride influx upon activation by GABA at the $\beta$ subunit.

Barbiturates

CNS depressants acting on the $\alpha/\beta$ interface of the $\text{GABA}_A$ complex to potentiate GABA and directly open chloride channels at higher doses, characterized by a narrow therapeutic index and hepatic microsomal enzyme induction.

Benzodiazepines (BZDs)

Hypnotic-anxiolytic drugs that bind the $\alpha/\gamma$ subunit interface of the $\text{GABA}_A$ receptor to enhance channel opening frequency in the presence of GABA, presenting a high therapeutic index.

Flumazenil

A specific competitive benzodiazepine receptor antagonist that blocks the effects of both BZD receptor agonists and inverse agonists, used to reverse BZD-induced sedation or toxicity.

Zolpidem

A non-benzodiazepine imidazopyridine hypnotic that selectively targets the $\omega_1$ ($\alpha_1$ subunit-containing) BZD receptor subtype, offering potent hypnotic and amnesic effects with minimal anticonvulsant or muscle relaxant actions.

Zaleplon

An ultra-short-acting pyrazolopyrimidine non-BZD hypnotic selective for the $\omega_1$ receptor subtype, indicated exclusively for sleep-onset insomnia (presomnia).

Doxylamine

An ethanolamine derivative and central $H_1$-histamine receptor antagonist used to treat presomnia and intrasomnia, frequently producing anticholinergic adverse effects.

Suvorexant

A dual orexin receptor antagonist (DORA) that blocks both $OX_1R$ and $OX_2R$ neuropeptide receptors in the hypothalamus to facilitate sleep onset and maintenance.

Agomelatine

A sleep-regulating antidepressant that acts as an agonist at melatonergic $MT_1/MT_2$ receptors and an antagonist at serotonin $5\text{-HT}_{2C}$ receptors to resynchronize circadian rhythms.

Phenytoin

A hydantoin antiepileptic that limits seizure spread by blocking voltage-dependent sodium channels; notable adverse effects include gingival hyperplasia, hirsutism, and fetal hydantoin syndrome.

Carbamazepine

An iminostilbene sodium channel blocker indicated as a first-line treatment for grand mal and partial seizures, with risks of neurotoxicity, aplastic anemia, and agranulocytosis.

Valproic Acid

A broad-spectrum antiepileptic that prolongs sodium channel inactivation, attenuates T-type calcium currents, and elevates GABA levels; known for risks of hepatotoxicity, pancreatitis, and neural tube defects (spina bifida).

Ethosuximide

A succinimide antiepileptic drug that acts selectively by blocking T-type calcium channels, used as a primary agent for treating absence seizures.

Levodopa

The metabolic precursor of dopamine that crosses the blood-brain barrier to be decarboxylated into dopamine, serving as a cornerstone treatment for Parkinson's disease.

Carbidopa

A peripheral DOPA-decarboxylase inhibitor that does not cross the blood-brain barrier, administered with levodopa to inhibit peripheral breakdown and diminish adverse effects like nausea and arrhythmias.

$D_1$-like Dopamine Receptors

Excitatory dopamine receptors ($D_1$ and $D_5$ subtypes) coupled to stimulation of adenylyl cyclase, resulting in elevated cAMP and protein kinase C activation.

$D_2$-like Dopamine Receptors

Inhibitory dopamine receptors ($D_2$, $D_3$, and $D_4$ subtypes) that inhibit adenylyl cyclase, promote potassium channel opening, and suppress voltage-sensitive calcium channels.

Dantrolene

A direct-acting skeletal muscle relaxant used in the clinical management of spasticity.