Neurochemistry, Synaptic Transmission, and Neuropharmacology

Comprehensive vocabulary flashcards covering synaptic transmission, neurotransmitter systems, receptor mechanisms, clinical correlates, and neuropharmacology from the lecture notes.

Optogenetics

A technique that combines genetics and optics by introducing genes encoding light-sensitive proteins into specific neurons to manipulate their electrical activity with light at millisecond precision.

Channelrhodopsin

A light-gated ion channel protein originally discovered in the single-celled alga Chlamydomonas that opens in response to blue light, allowing cations ($H^+$, $Na^+$, $Ca^{2+}$) to flow into the cell and induce depolarization.

Vagusstoff

The name given by Otto Loewi to the chemical substance released by stimulating the vagus nerve of a frog heart, which slowed the contraction of a second unstimulated heart and was later identified as acetylcholine.

Ionotropic Receptor

A neurotransmitter receptor protein incorporating an intrinsic ion channel (ligand-gated ion channel) that opens directly and rapidly in milliseconds upon ligand binding, generating brief and transient postsynaptic potentials.

Metabotropic Receptor

A G-protein-coupled receptor that acts indirectly through intracellular second messenger cascades upon neurotransmitter binding, producing slower (seconds to minutes) and longer-lasting alterations in cell physiology.

Curare

An arrowhead poison that acts as an antagonist by selectively blocking nicotinic acetylcholine receptors on skeletal muscle, leading to flaccid paralysis.

Bungarotoxin

A snake venom neurotoxin that binds to and blocks nicotinic acetylcholine receptors at the neuromuscular junction, preventing muscle contraction.

Acetylcholinesterase (AChE)

An enzyme present in the synaptic cleft that rapidly terminates acetylcholine signaling via degradation, splitting it into acetate and choline to be recycled by the presynaptic terminal.

Transporter

A specialized membrane protein located on the presynaptic axon terminal that brings released neurotransmitter molecules back inside the cell through reuptake for repackaging into synaptic vesicles.

Astrocytic Absorption

A synaptic clearance mechanism where surrounding glial cells absorb excess neurotransmitters, such as glutamate, from the synaptic cleft to prevent excitotoxicity and recycle metabolic precursors.

Glutamate

The most abundant amino acid neurotransmitter in the brain, functioning as the primary excitatory transmitter at over 90% of synaptic connections and acting on receptors such as AMPA and NMDA.

GABA (Gamma-aminobutyric acid)

The primary inhibitory amino acid neurotransmitter in the brain that prevents runaway neural excitation by opening $Cl^-$ channels via ionotropic $GABA_A$ receptors or acting through metabotropic $GABA_B$ receptors.

Catecholamines

A subfamily of monoamine neurotransmitters synthesized through a shared pathway starting from dietary phenylalanine and tyrosine, comprising dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline).

Indoleamines

A subfamily of monoamines synthesized from dietary tryptophan, which includes serotonin (5-hydroxytryptamine [5-HT]) and melatonin.

Mesostriatal Pathway

A dopaminergic neural circuit originating in the substantia nigra of the midbrain and projecting to the striatum (basal ganglia); it plays a crucial role in motor control and degenerates in Parkinson's disease.

Mesolimbocortical Pathway

A dopaminergic pathway originating in the ventral tegmental area (VTA) and projecting to the nucleus accumbens and cortex; it is central to reward, motivation, learning via positive reinforcement, and addiction.

Locus Coeruleus

A small noradrenergic brainstem nucleus that provides widespread noradrenaline projections to the forebrain to regulate vigilance, alertness, mood, and sympathetic activation.

Raphe Nuclei

Midline structures of the midbrain and brainstem containing serotonergic cell bodies that project rostrally to the forebrain and caudally to the spinal cord to regulate sleep, mood, appetite, and pain sensation.

Neuropeptides

Peptide neurotransmitters composed of short amino acid chains synthesized in the cell body and transported to terminals; they act slowly as neuromodulators to fine-tune synaptic function (e.g., oxytocin, substance P, endorphins).

Gasotransmitter

A gaseous signaling molecule, such as nitric oxide ($NO$) or carbon monoxide ($CO$), produced on demand in dendrites that diffuses directly across membranes to activate second messengers without synaptic vesicles or cell-surface receptors.

Agonist

A drug or endogenous ligand that binds to a neurotransmitter receptor and activates it, mimicking or enhancing normal transmitter function.

Antagonist

A substance or drug that binds to a receptor without activating it, physically blocking the receptor site and preventing endogenous neurotransmitters from binding.

First-Generation Antipsychotics

A class of neuroleptic drugs that reduce the positive symptoms of schizophrenia primarily by antagonistically blocking dopamine $D_2$ receptors.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressant medications, such as fluoxetine (Prozac) and citalopram (Celexa), that block presynaptic serotonin transporters to prolong the availability and action of serotonin in the synaptic cleft.

Benzodiazepines

A class of anxiolytic drugs that act as agonists on $GABA_A$ receptors, allosterically enhancing GABA-mediated inhibition to reduce central nervous system activity and anxiety.

Periaqueductal Gray

A midbrain region rich in metabotropic opioid receptors (delta, kappa, and mu) where endogenous opioids (enkephalins, endorphins) and exogenous opiates (morphine) act to suppress pain perception.

Delta-9-tetrahydrocannabinol (THC)

The major active psychoactive constituent of cannabis that binds to cannabinoid receptors in the brain to produce cognitive, emotional, and motor effects.

Biphasic Effect

A pharmacological response profile in which a substance produces opposite behavioral outcomes over time, such as alcohol inducing an initial stimulant phase followed by a depressant phase.

Fetal Alcohol Spectrum Disorder (FASD)

A developmental disorder caused by heavy prenatal maternal alcohol consumption, characterized by permanent neuroanatomical damage such as the agenesis or severe hypoplasia of the corpus callosum.

Insula

A region within the cerebral cortex implicated in addiction and craving; damage to this structure has been documented to allow individuals to quit addictive habits like cigarette smoking effortlessly.