Why do psychostimulants sometimes produce a calming effect? Flashcards
What is a readily releasable pool?
Vesicles that stay close to the synapse
- these release NTs under normal circumstances
Do all of the catecholamines have the same synaptic transporter?
Yes
What is the PRIMARY DA signal termination?
Through reuptake via the dopamine transporter
What is the other way that DA’s signal can be terminated?
Through two enzymes metabolizing the NT:
- COMT
- MAO
- both of these break down monoamines
Which transporter does dopamine have the highest affinity to?
NET (norepinephrine’s transporter) vs. its own (DAT)
Which receptors do epinephrine and norepinephrine act on?
Adrenergic receptors
What are the two families of adrenergic receptors?
Alpha (1, 2) and beta (1, 2, 3)
Which part of the PNS does epinephrine act on?
The sympathetic NS (to activate the fight/flight response)
Where do the cell bodies of NE lie? Where do these neurons project to?
NE cell bodies lie in the locus ceruleus and project to the cortex, thalamus and hypothalamus
What are the cortex, thalamus and hypothalamus important for? What have these areas been implicated in?
Orienting response (hypervigilance) - have been implicated in depression and anxiety
What is a reserve pool?
Vesicles waiting for sustained firing
Why do beta blockers have a calming effect?
because when they are bound, they prevent the heart from beating too quickly
Which two co-factors does tyrosine hydroxylase need in order to regulate DA synthesis?
- O2 (oxygen)
2. BH4 (pteridine co-factor)
If a receptor is presynaptic, what can we say about its function?
That it is presynaptic
What do the DA autoreceptors do when too much DA is bound to the D2 autoreceptors?
They phosphorylate tyrosine hydroxylase
What are 4 ways to control DA neurotransmission?
- end product inhibition?
- BH4 availability (BH4 must be synthesized)
- DA autoreceptors phosphorylate TH
- controlling the firing rate of DA neurons (increased firing causes TH to make more DA, which increases BH4 affinity)
What are the two major DA pathways?
- The nigrostriatal pathway
2. The mesocorticolimbic pathway
Describe the nigrostriatal pathway.
Cell bodies lie in the substantia nigra and project to the dorsal striatum (aka caudate nucleus aka putamen)
Describe the mesocorticolimbic pathway.
Cell bodies lie in the ventral tegmental area and project to the ventral striatum (aka nucleus accumbens) and the prefrontal cortex
What effect do all psychostimulants have on the receptors they bind to?
They all act on the dopamine transporter, causing DAT to pump DA out instead of sucking it back in
- they also work on the NE transporter, and the 5-HT transporter (they have a higher affinity to NET than DAT)
What is ADHD characterized by?
- hyperactivity
2. attention deficits
Which of dopamine’s two pathways is degenerated in Parkinson’s disease?
The nigrostriatal pathway (which is responsible for initiation of movement, habit learning, and motor learning
What is the prefrontal cortex responsible for?
- inhibition
- working memory
- executive function
What did Patricia Goldman-Rakic research?
She gave administered DA agonists in the pfc to primates and observed an increase in memory deficits
- she also gave DA antagonists and observed the same memory deficits
How can we describe the effect that DA has on working memory?
In terms of the Yerkes-Dodson law (not enough DA impairs memory, and too much DA does the same thing; there is a sweet spot of DA concentration where memory is at its peak)
