Neurotransmitters And Receptors

Front 1

G-protein type receptor

Back 1

Seven transmembrane receptor, requires G-protein to open ion channels. NH₂terminal outside the cell. Intracellular COOH terminal.

Front 2

ligand-gated ion channel receptor

Back 2

Ion channel as part of its structure that opens in response to binding of ligand to receptor

Front 3

voltage-gated ion channel

Back 3

Ion channel (Ca++) that opens in response to depolarization.

Front 4

neurotransmitters linked to aggression

Back 4

Decreased serotonin in CSF has been linked to agression. Dopamine seems to promote aggression, while NE, 5HT and GABA seem to inhibit it.

Front 5

second messengers - what are they?

Back 5

molecules that work within the cell to carry on the message delivered by the neurotransmitter on the cell surface. IP₃cGMP, Ca++, cAMP, DAG, NO and CO are all common second messengers

Front 6

receptor types associated with glutamate

Back 6

AMPA, kainate, NMDA

Front 7

receptor types associated with acetylcholine

Back 7

nicotinic1 - ganglionic
nicotinic2 - skeletal muscle
muscarinic

Nicotinic AChRs are ionotropic receptors permeable to sodium, potassium, and chloride ions. They are stimulated by nicotine and acetylcholine. They are of two main types, muscle type and neuronal type. The former can be selectively blocked by curare and the latter by hexamethonium. The main location of nicotinic AChRs is on muscle end plates, autonomic ganglia (both sympathetic and parasympathetic), and in the CNS.
Muscarinic receptors are metabotropic, and affect neurons over a longer time frame. They are stimulated by muscarine and acetylcholine, and blocked by atropine. Muscarinic receptors are found in both the central nervous system and the peripheral nervous system, in heart, lungs, upper GI tract and sweat glands.

Front 8

receptor types associated with NE

Back 8

alpha1 - usually excitatory
alpha2 - usually inhibitory
beta1 - usually excitatory
beta2 - usually inhibitory

Front 9

Receptor types associated with opioids

Back 9

delta, mu

Front 10

Glycine

Back 10

Synthesized from serine. A neccesary adjunctive neurotransmitter at NMDA receptor that binds with glutamate. Also an independent inhibitory neurotransmitter with own receptors that open chloride channels. Highest receptor concentration is in spinal cord.

Front 11

Amino acid neurotransmitters

Back 11

GABA, glutamate, aspartate. GABA is main inhibitory, glutamate is main excitatory. Benzodiazepines, barbiturates and some anti-convulsants affect GABA-A receptors. Lioresal (bacolofen) a muscle relaxant works at GABA-B. PCP affects glutamate receptors. Cocaine not only blocks reuptake of NE, DA and 5-HT, it also increases glutamate in nucleus acumbens.

Front 12

Sympathetic neurotransmitter at effector site

Back 12

norepinephrine

Front 13

Parasympathetic neurotransmitter at effector site

Back 13

acetylcholine

Front 14

Neurotransmitter at synapse with skeletal muscles

Back 14

acetylcholine

Front 15

5-HIAA

Back 15

5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin in the human body. In chemical analysis of urine samples, 5-HIAA is used to determine the body's levels of serotonin.

Front 16

catecholamine - summary information

Back 16

Catecholamines are chemical compounds derived from the amino acid tyrosine containing catechol and amine groups. Some of them are biogenic amines. Catecholamines are water-soluble and are 50% bound to plasma proteins, so they circulate in the bloodstream. The most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine, all of which are produced from phenylalanine and tyrosine. Tyrosine is created from phenylalanine by hydroxylation by the enzyme phenylalanine hydroxylase. (Tyrosine is also ingested directly from dietary protein). It is then sent to catecholamine-secreting neurons. Here, many kinds of reactions convert it to dopamine, to norepinephrine, and eventually to epinephrine.[1] Catecholamines are hormones that are released by the adrenal glands in situations of stress such as psychological stress or low blood sugar levels.

Catecholamines are produced mainly by the chromaffin cells of the adrenal medulla and the postganglionic fibers of the sympathetic nervous system. Dopamine, which acts as a neurotransmitter in the central nervous system, is largely produced in neuronal cell bodies in two areas of the brainstem: the substantia nigra and the ventral tegmental area.

Front 17

catecholamine synthesis

Back 17

-- precursor - tyrosine
-- tyrosine to dihydroxyphenylalanine (DOPA) rate limiting step for all cathecholamines. Cytoplasmic reaction - tyrosine hydroxylase.
-- DOPA to dopamine cytoplasmic reaction - dopa decarboxylase.
-- Dopamine to NE occurs in vesicles - dopamine beta hydroxylase.
-- NE to EPI occurs in some adrenergic neurons and adrenal gland - PNMT
-- storage pools are bound vesicular, free vesicular and free cytoplasmic (this last one regulates synthesis by inhibiting tyrosine hydroxylase.

Front 18

catecholamine release

Back 18

-- exocytotic: calcium enters cell during depolarization.
-- non exocytotic: calcium independent, pharmacologically important, not physiologically important, drug induced by cocaine, amphetamine and tyramine.

Front 19

fate of released catecholamine

Back 19

majority is taken up (reuptake) and reused, some is metabolized, and some bound to extraneuronal proteins.
Presynaptic reuptake is the primary mechanism, and is stored or metabolized by MAO. MAO also in liver, lungs, kidneys and GI tract.
Backup reuptake mechanism is extraneuronal, metabolized by COMT COMT is in postsynaptic tissue, liver, lungs and kidneys.

Front 20

acetylcholine summary information

Back 20

The chemical compound acetylcholine (often abbreviated ACh) is a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and the only neurotransmitter used in the somatic nervous system. It is also the neurotransmitter in all autonomic ganglia.
In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system. . When acetylcholine binds to acetylcholine receptors on skeletal muscle fibers, it opens ligand gated sodium channels in the cell membrane. Sodium ions then enter the muscle cell, stimulating muscle contraction. Acetylcholine, while inducing contraction of skeletal muscles, instead induces decreased contraction in cardiac muscle fibers. This distinction is attributed to differences in receptor structure between skeletal and cardiac fibers.
In the autonomic nervous system, acetylcholine is released in the following sites: all pre- and post-ganglionic parasympathetic neurons all preganglionic sympathetic neurons preganglionic sympathetic fibers to suprarenal medulla, the modified sympathetic ganglion; on stimulation by acetylcholine, the suprarenal medulla releases epinephrine and norepinephrine some postganglionic sympathetic fibers sudomotor neurons to sweat glands.
In the central nervous system, ACh has a variety of effects as a neuromodulator, e.g., for plasticity and excitability. Other effects are arousal and reward. Damage to the cholinergic system in the brain has been suggested to play a role in the memory deficits associated with Alzheimer's Disease.

Front 21

acetylcholine synthesis

Back 21

Acetylcholine is synthesized in certain neurons by the enzyme choline acetyltransferase from the compounds choline and acetyl-CoA. This is a cytoplasmic reaction.

Front 22

acetylcholine termination

Back 22

No active reuptake. The enzyme acetylcholinesterase converts acetylcholine into the inactive metabolites choline and acetate. This enzyme is abundant in the synaptic cleft, and its role in rapidly clearing free acetylcholine from the synapse is essential for proper muscle function. Certain neurotoxin work by inhibiting aceylcholinesterase, thus leading to excess acetylcholine at the neuromuscular junction, thus causing paralysis of the muscles needed for breathing and stopping the beating of the heart.