DA
4-(2-aminoethyl)benzene-1,2-diol
see dopamine systems
neurotransmitter, hormone (catecholamine), neuromodulator
see dopamine systems
usually but not necessarily excitatory
e.g. hoebel spent most of his career studying dopamine in reward (midbrain nuclei like nucleus accumbens) - release of dopamine there like a generalised reward signal
midbrain to PFC - imbalances in this projection supposed to be related to schizophrenia - too much dopamine
schizophrenia - can get motor deficits as a result of reducing dopamine
medication
affects sympathetic nervous system, increases heart rate and blood pressure
also important in frontal cortex
involved in attention deficit disorder and schizophrenia
associated with pleasure system
amphetamines force dopamine out of vesicles and into synaptic cleft
cocaine - inhibits dopamine reuptake by blocking dopamine transporter
role in experiencing pleasure has been questioned
may be more involved in appetitive than consummatory pleasure
6-hydroxydopamine used to deprive rats of dopamine (Berridge & Robinson, 1998)
no longer eat by their own volition
then force fed the rats
judging from facial expressions
did not reduce consummatory plesaure, only the desire to eat
mutant hyperdopaminergic mice showed higher wanting but not liking of sweet rewards (Pecina et al, 2003)
antipsychotics reduce dopamine activity (Lambert et al, 2003)
reduce motivation
cause anhedonia (inability to experience pleasure)
D2/D3 agonists (pramipexole and ropinirole)
sociability
social anxiety
tied to low D2 receptor binding
social withdrawal, apathy, anhedonia
my be related to dopamine deficiency
traits found in schizophrenia
dopamine-blocking antipsychotics alleviate manic hyperosociality and hypersexuality
may be involved in salience of rewarding or dangerous things
pars compacta projects dopamine to the go and no-go guys
direct pathway gives positive feedback, indirect pathway gives negative feedback
high dopamine = a go signal
low levels of dopamine = suppress response
dopmainergic inputs to both pathways facilitate movements initated in the cortex
since dopamine boosts go and inhibits no-go units
tonic vs phasic dopamine???
ks4, 867
if correct, you get a positive dopamine burst (pars compacta activity above baseline), which increases the go guys and decreases the no-go guys
if you're wrong, vice versa
if the response mapping is really consistent, then once the basal ganglia has settled into habitual responses, the slow cortical learning can generate the correct response on its own
both neuromodulator and neurotransmitter
come from one place and go all over
modulate states
hormone-like
local effect
see ks4 890 - major modulatory system of the brain
peptides are neurotransmitter
mesolimbic system
ventral tegmental area -> nucleus accumbens -> limbic system???
from sara
how is this different nigrostriatal???
intentional movement
both neuromodulators
disorders
schizophrenia, adhd, parkinsons
depression???
depression, ocd, tourettes, schizophrenia
ptsd???
Conversation - Jon Roiser, 031031
if you take out the raphe nuclei and the cholinergic system, it messes up memory
but raphe on their own doesn't affect memory
what about ACh on its own???
cf schultz
prediction error in ventral tegmental area