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Flashcards in Neurotransmitters & Recptors Deck (37)
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Distribution of Cholinergic neurons

-cholinergic neurons in vertebrate NS
-motor neurons
-Autonomic NS
1. Preganglionic sympathetic and parasympathetic
2. postganglionic parasympathetic
-neurons regulating arousal and sleep in brainstem and forebrain
-local interneurons in other brain regions
-project locally within the region


Synthesis, release, removal of acetylcholine

-synthesized from precursors in Acetyl-CoA and choline in presynaptic terminal
-loaded into SVs by vesicular transporter
-degraded in cleft by acetylcholinesterases (leaves choline which is taken up
-acetate diffuses away


Nicotine acetylcholine receptors

-ionotropic receptors permeable to cations
-fast EPSPs
-structure: 5 subunits + several genes for diversity
-at NMJ
-pre and post ganglionic parasympathetic
-preganglionic sympathetic
-many cholinergic synapses in brain
-nicotine, a-bungarotoxin, curare act on nicotine receptors


Muscarinic acetylcholine receptors

-metabotropic receptors
-activation leads to decrease or increase in K+ conductance
-slower EPSPs/IPSPs
-targets of parasympathetic innervation (heart, smooth muscle)
-forebrain regions (striatum)
-blockers: atropine (pupillary dilation), scopolamine (prevents motion sickness), ipreatopium (asthma treatment)


Myasthenia Gravis

-disease that interferes with neurotransmission at NMJ
-faster fatigue during repetitive stimulation
-mEPPs smaller
-cause: autoimmune disease
-antibodies against nAChRs generated
-treatment: acetylcholine esterase inhibitors
-less degradation of acetylcholine


Distribution of Glutamate

-NT of most excitatory synapses throughout CNS
-more than 50% of all synapses in the brain
-NT of many primary sensory cells (photoreceptors, olfactory receptors)


Synthesis, release and removal of glutamate

-synthesized from glutamine in presynaptic terminal
-loaded into SVs by vesicular transporter
-released glutamate taken up into glia and neurons by excitatory aa transporters
-glutamine taken up by glia is converted to glutamine and shuttled back to neurons


Ionotropic glutamate receptors

-AMPA, NMDA, Kainate
-all cation permeable
-all have 4 subunits and multiple genes
-most glutamatergic synapses in brain have AMPA and NMDA
-Kainate receptors present at some synapses


NMDA receptors

-permeable to cations; calcium activates postsynaptic signalling pathways
-at negative membrane potentials, channel pore blocked by Mg2+
-opens only in response to glutamate release and post synaptic depolarization
-glycine or D-serine as coagonist


Metabotropic glutamate receptors

-3 groups
-post- and presynaptic localization
-postsynaptic: trigger second messenger cascades modulating excitability
-presynaptic: diminish NT release (inhibitory)


GABA and glycine distribution

-GABA is an amino acid NT
-most abundant inhibitory NT in brain (30% of synapses)
-glycine mainly at inhibitory synapses in spinal chord


GABA synthesis, release, removal

-synthesized from glutamate in presynaptic terminal
-SV loading by vesicular inhibitory AA transporter
-released GABA taken up into glia and neurons by GABA transporters


Glycine synthesis, release, removal

-synthesized from serine in presynaptic terminal
-SV loading by vesicular inhibitory aa transporter
-released glycine taking up into glia and neurons by glycine transporter


Ionotropic GABA and glycine receptors

-permeable to Cl- (usually IPSP)
-structure: 5 subunits, several genes
-benzodiazepines and barbiturates: positive modulators; used as sedatives, anxiolytics, and anticonvulsants
-bind to channel and allow them to be open longer... more Cl- influx repolarizing membrane

Glycine receptors: permeable to Cl-
-inhibited by strychnine (causes convulsions... uncontrolled excitation)


Metabotropic GABA receptors

-Activation of G proteins leads to increase K+ conductance
-slow IPSPs
-presynaptic GABAB receptors diminish NT release


Distribution and function of dopamine

-substantia nigra and ventral tegmental area
-project to cortex and striatum
-facilitation of body movement (Parkinson’s)
-motivation and reinforcement (addiction)
-regulate cognitive functions (psychiatric disorders)


Synthesis and removal of dopamine

-synthesized from tyrosine
-released DA taken up into glia and neurons by domaine transporters
-DAT inhibited by cocaine, so in synapse longer
-DA degraded in neurons by monoamine oxidase
-MAO inhibitors used as antidepressants (prevents breakdown)


Dopamine receptors

-only metabotropic
-receptor activation can lead to increase or reduced post synaptic excitability (depending on which G protein)
-DA antagonists used to treat schizophrenia
-L-DOPA (precursor of DA) used to treat Parkinson’s symptoms


Distribution and function of norepinephrine

-sympathetic ganglia
-fight or flight
-locus coeruleus in brain stem
-influences sleep and wake


Distribution and function of epinephrine

-in rostral medulla
-involved in autonomic functions
-adrenal glands produce 80% of epinephrine (20% of norepinephrine)


Norepinephrine and Epinephrine synthesis and removal

-NE synthesized from DOPAMINE
-released NE taken up into glia and neurons by NE transporter
-NET inhibited by amphetamines
-degraded in neurons by MAO
-MAO used as antidepressants


Adrenergic receptors

-bind E and NE
-different classes for different G proteins
-increase or decrease excitability
-peripheral: smooth muscle contraction/relaxation
-increased heart and muscle force
-glandular secretion
-antagonists and agonists used pharmacologically
-beta blockers (decrease excitability)


Distribution and function of serotonin

-in raphe nuclei
-sleep and wake
-mood and emotions


Synthesis and removal of serotonin

-synthesized from tryptophan
-taken up into glia and neurons by serotonin transported
-SERT inhibitors used as antidepressants
-degraded by MOA


Serotonin receptors

-also called 5-HT receptors
-metabotropic receptors with different classes
-increase/decrease excitability
-also 1 group of ionotropic receptors
-non-selective, mediate fast EPSPs


Histamine distribution and function

-in hypothalamus
-regulate sleep and wake
-antihistamines have sedative effect


Histamine synthesis and removal

-synthesized from histidine
-taken up into glia and neurons
-degraded by MAO


Histamine receptors

-increase or decrease excitability


Purines distribution and function

-Purine NTs: ATP and adenosine
-ATP in all SVs
-coreleased with other NTs
-adenosine generated through breakdown of ATP in extracellular space

-neuron - glia communication
-respiratory response to hypoxia


Purinergic receptors

-3 classes: P1, P2Y, P2X
-P2X only ionotropic receptor
-all classes expressed throughout NS and in neuronal tissue
-caffeine blocks P1: responsible for stimulant effect