Neurotransmitters Flashcards
Glutamate
Major excitatory NT in CNS
Post-synaptic receptor type can be ionotropic or metabotropic
Ionotropic receptor: NMDA, kainate AMPA
When receptor is ionotropic, always excitatory
When receptor is metabotropic, can be excitatory or inhibitory
Amino acid
Function:
1.Excitatory neurotransmission-AMPA/Kainate receptor
2.Modulation of synaptic plasticity-NMDA receptor
3.Activation of second messenger system-Metabotropic receptor
Cell bodies and projections in CNS
GABA
Amino acid Major inhibitory NT of CNS Ionic and metabotropic post-synaptic receptors Function: 1. Inhibitory neurotransmission
Receptors:
Entire CNS: GABA a, GABA, b
Retina: GABA c
Transmission impacted by many drugs, such as anti-anxiety, hypnotics, anti-epileptics, and aesthetics
Dopamine
Cell bodies in midbrain (substantia nigra, pars compacta, and ventral tegmental area)
Project on striatum, prefrontal cortex, lambic cortex, nucleus accumbens, amygdala
Receptor D1-5
Causes neuromodulation; involved in reward-motivated behavior and motor pathways
CNS neurons originate in brainstem regions
3 pathways: mesolimbic (reward pathway/addiction), nigrostriatal (control of movement), and mesocortical (working memory)
Drugs that influence dopamine transmission: antipsychotics, nicotine, Cochin, methamphetamine, amphetamines, and methylphenidate
Serotonin
Cell bodies in midbrain and pons (raphe nuclei) and project onto entire CNS
Receptors: 5-HT1A-F, 5HT2A-C’, 5HT3-7
Neuromodulation
Histamine
Cell bodies in hypothalamus and project onto brain
Receptor: H1-3
Mainly excitatory neuromodulation
Definition of NTs
- Synthesized in pre-synaptic neuron
- Reside in synaptic terminal, usually vesicles
- Elicit same response when tested under in-vitro conditions
- Bind to specific receptors on post-synaptic membrane
- Inactivated in or removed from synaptic cleft
Major 6 NTs
Glutamate (excitatory AA) GABA (inhibitory AA) Dopamine (biogenic amine) Norepinephrine (biogenic amine) Serotonin (biogenic amine) Acetylcholine
Synaptic vesicles
Protect NT from degradation
Transported to nerve terminals and aggregate in presynaptic region
Motored by V-type H+ ATPase: uses a proton gradient to exchange H+ for NT
NMDA Receptor
Voltage gated and ligand gated Ca2+ glutamate ionotropic receptor
Activated by the binding of glutamate to AMPA, which allows for Na+ to enter post-synaptic neuron and depolarize the cell. Once depolarized, Mg2+ is displaced and NMDA is active
Blocked by Mg2+ at RMP
When blocked by PCP and ketamine, causes hallucinations that resemble schizophrenia
Important for development of synapses, regulating neural circuits, and long term potentiation (increased responsiveness of post-synaptic neurons after repeated stimulation)
Glutamate exotoxicity
Occurs in many diseases such as ALS, Alzheimer’s, tumors, oxygen deficiency, ischemia, trauma, and repeated seizures.
When there is increased glutamate release or decreased glutamate reuptake, causing increased Ca2+ leakage into cells
Increased Ca2+ causes increased water uptake and stimulation of intracellular enzymes that degrade proteins, lipids, and nucleic acids
Cell death
Neuromodulators
Subclass of NTs that usually originate in the brainstem and project widely throughout the cortex
Affect wakefulness, attention, personality, motivation, reward pathway, etc
Muscarinic receptors
Excitatory or inhibitory depending on the receptor
Target for many psychiatric drugs
ANS receptor of dilator muscle in eye
Alpha adrenergic
When epi or norepi bind, cause pupillary contraction to increase pupil size (mydriasis)
ANS receptor of sphincter (pupillary constrictor muscle)
Muscarinic
When ACh binds, mediates contraction causing miosis
ANS receptor of ciliary muscle
Muscarinic
Binding of ACh, controls accommodating and contraction puts tension on trabecular mesh work to facilitate aqueous humor outflow.
ANS receptor of ciliary epithelium
Beta adrenergic
Promotes secretion of aqueous humor by
