Adrenoreceptors Flashcards
Which drug effects the synthesis stage of NE?
- Reserpine blocks VMAT and inhibits vesicular transport
- alpha methyl tyrosine inhibits tyrosine hydroxylase enzymes and in experimental conditions can be used for the inhibition of synthesis of NE
which drugs affect the storage of NE?
Indirect sympathomimetics like tyramine and sympathomimetics of mixed actions like ephedrine promote the release of NE from its storage
which drugs affect the release of NE?
- Phentolamine presynaptic A2 receptors and increases and NE into the synaptic cleft due to suppression of negative feedback mechanism
- Clonidine decreases the release of neurotransmitter in case of stimulation of presynaptic A2 receptors
- Propranolol inhibits presynaptic beta 2 receptors and it decreases the release of neurotransmitters
which drugs affect the inactivation of released NE?
- Tricyclic antidepressants or cocaine inhibit the neuronal uptake or reuptake 1
- Clorgyline and selegyline inhibit MAO enzyme
- Tolcapone and entacapone inhibit COMT enzyme
What are the different types of adrenoreceptors?
- Alpha 1
- postsynaptic alpha 2
- presynaptic alpha 2
- beta one
- postsynaptic beta 2
- pre synaptic beta 2
- extra synaptic beta 2
- beta 3
What is the transduction mechanism of alpha 1 adrenoreceptors?
They couple with Gq protein and activate phospholipase C leading to increase of IP3 and DAG
where can we find alpa 1 adrenoreceptors?
- Smooth muscles
- Eyes
- blood vessels
- heart
- spleen
- GIT
- Uterus
- Pilomotor muscles of the skin
what are the actions of stimulating alpha 1 adrenoreceptors?
- contraction of radial papillary dilator muscle of the Irish causing mydriasis
- vasoconstriction of ciliary body vessels and inhibition of production of fluid causing decrease of intraocular pressure
- vasoconstriction of skin, renal, cerebral, and GIT vessels
- insignificant contraction of bronchial smooth muscles
- insignificant increase of heart contraction force
- rise in blood pressure
- constriction of spleen capsule and shifting deposited blood into the bloodstream
- contraction of sphincters of GIT and urine bladder
- decrease in tone and motility of stomach and intestine
- contraction of uterine
- contraction of pilomotor muscles of skin causing gooseflesh
What is the transduction mechanism of alpha 2 adrenoreceptors?
They couple with GI proteins and inhibit adenylate cyclase and reduce the level of intracellular C AMP and increase in permeability of potassium ions and inhibition of calcium channels
what is the location of postsynaptic alpha 2 adrenoreceptors?
- CNS
- GIT
- Intestines
- adipose tissues
what are the observed actions in case of stimulating postsynaptic alpha 2 adrenoreceptors?
- Inhibition of central sympathetic outflow resulting in the decrease of blood pressure and bradycardia
- sedative and analgesic actions
- increased blood pressure
- decrease of motility of GIT
- inhibition of secretory functions of intestines
- inhibition of AMP dependent lipolysis and adipose tissues
where can we find presynaptic alpha 2 adrenoreceptors and what are the actions observed due to their stimulation?
They are found in juxtaglomerular system of kidneys at which their activation results in the inhibition of the release of NE from peace synaptic membrane and leads to the inhibition of renin secretion
what are the actions observed in case of stimulating extra synaptic alpha 2 adrenoreceptors?
- Contraction of ciliary body vessels, decrease in intraocular fluid formation, and reduced intraocular pressure
- vasoconstriction of the skin and mucous vessels
- inhibition of insulin secretion
- stimulation of platelet aggregation
What is the transduction mechanism of beta adrenoreceptors?
They are coupled with GS protein at which their activation and cardiomyocytes open calcium channels and and smooth muscles leads to activation of protein kinase a which inhibits the activity of miocene light chain calmodulin dependent kinase
what are the locations of beta 1 adrenoreceptors?
- CNS
- Heart
- Kidneys
- Intestine
- fatty tissues
