Beyond the Amygdala Flashcards
What is the role of the hippocampus?
Lesions have anxiolytic effects - increase in the rate of acquisition of active avoidance, don’t show freezing behaviour - may be changing how the amygdala is responding
It provides information about contextual stimuli that are important for fear conditioning - if you pair 2 things, get a freezing behaviour just where you learnt it - this is the role
What do benzodiazepines do to the hippocampus?
They have a direct effect on GABAergic inhibition in the hippocampus - decrease in contextual fear response when midazoplam is administered directly into the hippocampus
What happens in situations of chronic stress?
Activation of glucocorticoid receptors in hippocampus
increased Ca2+
too much, cells die
hippocampus can’t feed back to limit cortisol production
so some anxiety disorders my result from diminished activity of the hippocampus, loss of feedback to the amygdala, inappropriate fear responding
Where else do the hippocampus and amygdala respond too?
Diffuse modulatory ssystems:
noradrenergic system
serotonin system
both project diffusely throughout the brain, they balance one another e.g. serotonin inhibits LC firing
What is the role of the locus coeruleus?
When activated from events that are important for survival, there is increased firing of LC (more noradrenaline), increased arousal and attention - focussing on what is happening, gets you ready to deal with what is going on - but overactive is bad
What do benzodiapines do to the LC?
Decrease the release of noradrenaline in the LC (increased GABA inhibition of NA neurons) - these don’t do anything alone, but in a stressful environment, it is released, and BDZ can block the arousal
if overactive - get rid of the symptoms of feeling fearful
What is the role of the raphe nuclei?
Serotonergic projections to the brain
Punishment stimuli - leads to activation of sertonergic system - behavioural inhibition (freezing) - shuts you down
Opposing system to noradrenaline
What do benzodiazepines do to the raphe nuclei?
They decrease the serotonergic activity in the raphe nuclei - increase in social interaction (anxiolytic effect) following administration of midazolam directly into the raphe nuclei, increasing inhibition
What are the two opposing systems?
Noradrenergic system - associated with arousal (sympathetic nervous system)
Serotonergic system - associated with behavioural inhibition (central nervous system symptoms)
What do benzodiazepines work well for and what do they not work well for?
Work well in:
Generalised anxiety disorder
Panic disorder
Not effective in:
OCD and PTSD
What do SSRI work for?
OCD
PTSD
PD
GAD
What are the problems with SSRI’s?
They can be anxiogenic in the first few days of treatment, takes a while for them to work - problematic if feeling bad
sometimes prescribe them at the same time as a low dose of BZD to treat this
Common treatments for anxiety disorders
Benzodiazepines
SSRI’s
Buspirone
What is buspirone?
5-HT receptor partial agonist - works for GAD, but takes a while
What do SSRI’s do?
Prolong the action of 5-HT (serotonin) in the synapse - can’t do it without serotonin, need that first to release more
or it could be that the presynaptic terminal is feeding back to say stop getting it
