CNS Neurotransmitters Flashcards
Presynaptic Inhibition
Some CNS nerve terminals synapse on other (excitatory) pre-synaptic terminals; an action potential in the inhibitory terminal releases GABA, which opens chloride channels in the target pre-synaptic terminal and ‘short-circuit’ the action potential in the excitatory terminal, reducing the number of voltage-gated Ca2+ channels that open in response to the action potential; thus, less excitatory neurotransmitter is released
Spatial summation
Many excitatory inputs converge on a target and fire action potentials simultaneously; each individually small synaptic potential summates, driving the post-synaptic membrane potential toward threshold
Temporal summation
A single excitatory input stimulated in succession causes a larger EPSP due to synaptic facilitation (Ca2+ accumulation)
Function of ACh in the CNS
Coordinated movement and cognitive functions (motivation, memory, and learning)
Pathophysiological Role of ACh in CNS
Alzheimer’s Disease
Parkinson’s Disease
Schizophrenia
Synthesis of Dopamine
Tyrosine is convered into L-Dopa by Tyrosine Hydroxylase (TH); L-Dopa is converted to Dopamine
Synthesis of Serotonin
Tryptophan is converted to 5-OH-tryptophan by Tyrosine Hydroxylase; 5-OH-tryptophan is then converted to Serotonin (5-HT)
Storage of monoamines
Transmitter is taken up into the storage vesicle via the vesicular monoamine transporter (VMAT)
Monoamine oxidase (MAO)
Enzymatically destroys dopamine, norepinephrine, and serotonin
Termination of monoamine signaling
Synaptic activity of monoamines is terminated mainly by pre-synaptic membrane transporters: dopamine transporter (DAT), norepinephrine transporter (NET), serotonin transporter (SERT)
Function of Dopamine in CNS
Initiation of voluntary movement
Reward related behaviors
Working memory
Attention
Function of NE in the CNS
Arousal, attention, vigilance
Sleep-wake cycle
Fear, anxiety
Mood/emotion
Function of Serotonin in the CNS
Arousal, attention, sleep
Processing of sensory information
Emotion, mood regulation
Eating/drinking behaviors
Pathophysiological role of Dopamine in CNS
Schizophrenia
Parkinson’s Disease
OCD
ADHD
Pathophysiological role of NE in CNS
Mania
Depressio
Anxiety disorders
ADHD
Pathophysiologic role of Serotonin in CNS
Depression
Anxiety
Schizophrenia
Synthesis of GABA
GABA is synthesized from Glutamate via glutamic acid decarboxylase (GAD)
Termination of GABA signaling
Primarily reuptake into the pre-synaptic nerve terminal and surrounding glial cells by the GABA transporter
GABA(A) Channel - Function
Ionotropic; GABA binding opens ligand-gated Cl- channel, decreasing neuronal excitability via ISPs
GABA(B) Channel - Function
Metabotropic; Gi/o coupled, inhibits adenylyl cyclase, decreases Ca2+ conductance, opens K+ channel
Pathophysiological Role of GABA in CNS
Generalized anxiety disorder
Seizure disorders
Sleep disorders
Alcohol withdrawal
Synthesis of Glutamate
Glutamate is formed from Glutamine by the action of glutaminase in the nerve ending
Glutamate termination and storage
Released glutamate either re-enters the neuron via neuronal glutamate transporter [(Gt(n)] or is taken up by the glial cell transporter [(Gt(g)] and is converted to glutamine by glutamine synthetase (GluSyn)
Pathophysiological Role of Glutamate in CNS
Epilepsy
Ischemic brain damage
Addiction
Schizophrenia
