Sympathomimetics Flashcards
On what five groups of tissue can we find alpha 1 receptors?
- Most vascular smooth muscle
- Iris
- Pilomotor smooth muscle
- Prostate and Uterus
- Heart.
What actions do the alpha 1 receptors have on the tissues they are located on?
- Contraction of the vascular smooth muscle beds (blood vessels, sphincters and bronchi).
- Contraction of the radial muscle of the iris (which dilates the pupil = mydriasis).
- Erects hair via the pilomotor smooth muscle
- Contraction of the prostate and uterus
- Increases force of contraction of the heart.
Which five tissues do we see a response from alpha 2 receptors?
- Platelets
- Adrenergic & cholinergic nerve terminals (presynaptic)
- Vascular smooth muscle
- GI tract
- CNS
What actions do the alpha 2 receptors have on the tissues they are located on?
Cause:
- Aggregation of platelets
- Inhibit transmitter release from adrenergic and cholinergic nerve terminals
- Contraction of vascular smooth muscle post-synaptically or dilation presynaptically in the CNS.
- Relaxation of the GI tract presynaptically
- Sedation and analgesia in the CNS via decreased SNS outflow from the brain stem.
Why does blood vessel contraction not end up being a big deal with alpha 2 receptor activation?
Because the presynaptic postganglionic neuron alpha 2 receptors at the blood vessel act as ultra-short loop negative feedback as then release NE that NE feeds back to the receptor changing the potassium conductance and hyperpolarizing the cell inhibiting further release of NE.
Which tissue is more sensitive to lower levels of alpha 2 activation?
The brain.
What is the problem with antagonizing the alpha 2 receptor?
We lose our negative feedback and would end up with a shit ton of circulating NE.
What two main places are Beta 1 receptors found?
- Heart
2. Kidneys
What actions do the Beta 1 receptors have at their tissue sites?
- Increase the force and rate of contraction of the heart
2. Stimulation of renin release.
What six places do we find Beta 2 receptors?
- Visceral smooth muscle (respiratory, uterine, vascular GI, GU)
- Mast cells
- Skeletal muscle
- Liver
- Pancreas
- Adrenergic nerve terminals.
What actions does the Beta 2 receptor have at the tissue level?
- Promotes smooth muscle relaxation
- Decreases histamine release
- Potassium uptake, dilation of vascular beds, tremor and increased speed of contraction
- Glycogenolysis
- Increased insulin secretion
- Increased release of NE
Beta 3 targets? causing?
- Fat cells
2. Activates lipolysis and thermogenesis.
Which Dopamine receptor is found on smooth muscle?
D1
What kind of action does the D1 receptor cause to happen in the smooth muscle?
Post-synaptic location; dilates renal, mesenteric, coronary and cerebral blood vessels.
Which Dopamine receptor is found on nerve endings?
D2 receptor
What kind of action does the D2 receptor cause to happen in the nerve endings?
Pre-synaptic: modulates transmitter release (feedback); nausea and vomiting
Name the three endogenous catecholamines.
- Epi
- NE
- Dopa
Name two synthetic catecholaimines.
- Isoproterenol
2. Dobut
What two types of classes of synthetic non-catecholamines do we have?
- Indirect
2. Direct
Name 3 indirect acting synthetic non-catecholamines.
- Ephedrine
- mephenermine
- amphetamines
Name two direct acting synthetic non-catecholamines..
- Phenylephrine
2. methoxamine
Name two selective alpha-2 agonists.
- Clonidine
2. Dexmedetomidine
Name three selective beta-2 adrenergic agonists
- Albuterol
- terbutaline
- Ritodrine
Direct agonists have varied affinites for?
Alpha 1, Alpha 2, Beta 1 and Beta 2.
Indirect agonists….
increase the release of NT
In what four ways can catecholamines be terminated/metabolized?
- Reuptake
- MAO
- COMPT
- Lungs
What are the two different reuptakes for catecholamines?
- Uptake 1- neuronal reuptake (the neuron that released it takes it back)
- Uptake II- extraneuronal uptake (neighboring area, slower with lower affinity so not as avid of a reuptake)
In what two was are non-catecholamines terminated/metabolized?
- MAO
2. Urinary excretion (unchanged).
