Exam 2 Flashcards
(287 cards)
Catecholamines are named for their
structure
General term for neurotransmitters/hormones in sympathetic NS
Catecholamines
Three major catecholamines/neurotransmitters
Dopamine, Norepinephrine, + Epinephrine
Norepinephrine is located
On effector organs at adrenergic receptors of the sympathetic NS
Four basic categories of adrenergic receptors
- Alpha 1 type (a1a,b,c)
- Alpha 2 type (a2a,b,c)
- Beta type (b1,2,3)
- Dopamine type (d1,2,3,4,5)
Adrenergic receptors (alpha1, alpha2, beta, + dopamine) are all
G-protein coupled cell membrane bound receptors
What increases of complexity of the NS by adrenergic receptors (alpha1,alpha2,beta,dopamine)
Various subtypes differing by potency + type of response
Number of factors can alter degree to which any adrenergic receptors respond to a stimulus
- Selectivity
- Regulation
- Polymorphisms
- Catecholamines
- Why we see effect in one person but not others
Receptor selectivity allows
sympathomimetic drugs to bind to one subgroup of receptors w/out binding to others
-Drug X binds to a1 receptors but not a2/B
Selective binding results in
selective actions
Degree of binding in receptor selectivity is
concentration-dependent
Receptor selectivity at low concentrations allow for
selective binding
Receptor selectivity at high concentration cause
Non-selective binding
- larger concentration floods receptors that usually don’t bind drug
- high dose of drug X bind to both a + b
- more unintended effects
Receptor regulation
Response inc./dec. over time
*usually due to changes in number of receptors/Up-down regulation
Receptor regulation can result in
Changes of observed response to sympathomimetic drugs
Example of receptor regulation
Desensitization
Desensitization AKA
- Tolerance
- Refractoriness
- Tachyphylaxis
Desensitization occurs after
long term exposure to catecholamines/drugs
Desensitization results in
Dec. responsiveness of that cell/tissue to additional stimulation
Mechanisms of desensitization
- Altered transcription/translation of DNA+/RNA
- Modifications of receptors by interaction w/enzymes/other proteins
- Long term exposure to agonist often w/ long-term drug use
- Interactions/messages from other receptors
* Results in less effect
Sometimes desensitization of receptors is the
Desired effect of drug b/c increased response followed by the desired decreased physiologic action
Example of therapeutic desensitization
Drug z binds to a1 receptors + causes exaggeration of expected physiologic response but the body doesn’t like that and wants to maintain homeostasis so the body dec. production of a1 receptors in the target organ (down regulation) so less neurotransmitter available to bind to a1 receptors result in in desired effect of drug which is dec. in a1 activity in specific target organ
All people have a and B receptors but slight changes in ______can occur in different people
amino acid sequences
Amino acid differences in receptors can
Alter receptor response
- Inc./dec. risk to develop dz
- Degree of susceptibility to desensitization
- Degree of responsive to drug
- May be why some therapeutic drugs work in some patients but not others which is a key area of future genetic investigations