72 - Basics continued Flashcards
How long is half-life of amine hormones?
Peptide/protein hormones?
Steroid hormones?
- Monoamines: 1-3 min
- Peptide/ptn: 4-170 min
- Steroid: min - several hrs
What are the 2 classes of monoamines?
- Catecholamines
- Indoleamines
How do monamines travel in the blood?
Freely
Describe the pathway of formation of catecholamines (don’t give enzymes).
Tyrosine -> XDOPA -> Dopamine -> NE -> epi
Can catecholamines act as a hormone, NT, or both?
Both
What hormone is the exception to the monoamines?
TH (we will see)
What is the RLS of catecholamine catabolism?
Tyrosime -> XDOPA (*tyrosine hydroxylase)
- Tyrosine hydroxylase often used as a marker for dopaminergic activity
How long is the half-life of monoamines?
Very short (1-2, 3 minutes)
What enzyme converts NE to epi?
Phenylethanolamine-N-methyltransferase (PNMT)
In what 3 major brain areas is dopamine synthesized?
- VTA
- SN
- Arcuate nucleus
(reward pw’s, attn, food)
Besides the brain, what other gland makes dopamine?
What is it converted to there?
Adrenal gland
- Converted to NE
What is dopamine’s specific endocrine action?
it’s a NT as well as a hormone
Tonic inhibitor of PRL in ant. pit.
Dopaminergic neurons arise from the __________ of the hypothalamus.
Arcuate nucleus
Where does dopamine (directly) go upon its release from the arcuate nuc of the hypo?
Into the hypophyseal capillary bed
Does NE function as a NT, hormone, or both?
Both
What does NE require for its release?
Symp NS stimulation
What general type of cell convert most of the dopamine into NE?
Neuron
What enzyme converts dopamine to NE?
Dopamine beta-hydroxylase
What class of neurons release NE?
Sympathetic post-ganglionic neurons
What specific types of receptors does NE act on? (released from sympathetic post-ganglionic neurons)
Alpha and beta-andrenergic receptors
Where is NE converted to epi?
What nerve innervates this?
Adrenal medulla
- Splanchnic n.
What is the names of the types of cells that release NE/epi into the blood in the adrenal medulla?
Chromaffin cells (analogous to post-sympathetic neurons)
While post-ganglionic sympathetic cells secrete NE, pre-ganglionic cells secrete _________/
ACh
Recall: what substrate do catecholamines derive from?
Tyrosine
What substrate do indoleamines derive from?
Tryptophan
Describe the pathway of formation of indoleamines (don’t give enzymes).
Tryptophan -> Serotonin -> (intermediate) -> melatonin
What is the RLS of indoleamine catabolism?
Tryptophan hydroxylase (TPH)
What hormone is known as the “happiness hormone”?
Is it also a NT?
Serotonin (5-HT)
- Yes
95% of 5-HT is made in the ___________ via ___________ cells.
- Gut
- Enterochromaffin
What are 5-HT’s actions in the gut?
- Vasoconstriction of smooth mm.
- Smooth m. cell contractions in intestine
How do SSRIs work?
What are 2 possible issues w/them?
Block 5-HT reuptake, supposedly leaving them in synaptic cleft to work longer
- Desensitization/down-regulation of receptors
- Negative feedback–less 5-HT produced in pre-synaptic cells