alpha-2 agonists Flashcards
what are the 3 subtypes identified based on susceptibility to activation/inactivation by agonists and antagonists and confirmed by molecular biology
- a-2A: sedation, hypnosis, analgesia, sympatholysis
- a-2B: vasocontriction, anti-shivering action, analgesia
- a-2c: learning, startles response
what type of receptor is an a-2 adrenoceptor
G-protein coupled receptor
location of a-2 adrenoceptors
each receptor subtype is distributed ubiquitously throughout the body
presynaptic a-2 adrenoceptors
inhibit release of norepinephrine
postsynaptic a-2 adrenoceptors
norepinesphrine effect
a-2A receptors located presynaptically on neurons in the:
locus coeruleus
how is hyperpolarization mediated
by G-protein
what is the decreased sympathetic activity of a-2A
- decreased HR
- decreased BP
supraspinal level analgesic effects
activation of descending antioceptive pathways
spinal level (dorsal horn spinal cord)
pre/postysnaptic inhibition of nociceptive transmission
a-2 agonists vasocontriction effect
- hypertension, reflex bradycardia, cause decrease CO
- initial phase
- no atropine
a-2 agonists - decreased sympathetic tone
- hypotension, direct bradycardia, cause decrease CO
- secondary phase
- yes atropine
a-2 agonists - increased vagal tone
direct bradycardia, AV block
causes of medetomidine in dogs
- increase in systemic and pulmonary artery pressure
- decrease in HR (20-30%)
- decrease in CO (50%)
- increase in systemic and pulmonary vascular resistance
what do anticholinergics cause (bad)
- decrease in bradycardia
- arrhythmias
- hypertension
- decreased contractility, impaired myocardial oxygenation
