Beta-adrenoceptor blockers/antagonist Flashcards
What are adrenergic receptors?
- GPCRs - part of sympathetic system
What hormones activate adrenergic receptors?
- catecholamines - adrenaline and noradrenaline (main 2)
What are the 2 main groups of adrenergic receptors?
- alpha (a) - beta (B)
What type of transmembrane receptors are all adrenergic receptors?
- GPCRs
How many alpha adrenergic receptors are there?
- 2 - alpha 1 and 2
How many beta adrenergic receptors are there?
- 3 - B1, B2 and B3
Which GPCR do alpha receptors use to activate intracellular pathways?
- a1 = Gaq - a2 = Gai
Which GPCR do beta receptors use to activate intracellular pathways?
- all Gas
What is the basic intracellular pathway for Gaq?
- phospholipase C is activated and cleaves PiP
- IP3 and DAG are formed
- IP3 increases Ca2+
- Ca2+ binds with DAG and activates protein kinase C
- protein kinase C can phosphorylate inside cell
What is the basic intracellular pathway for Gas?
- adenlyly cyclase (AC) is activated
- AC converts ATP into cAMP
- cAMP activates protein kinase A
- protein kinase A can phosphorylate inside cell
What is the primary function of a1 adrenoreceptors receptors during fight or flight?
- vasoconstriction (primarily blood vessels)
- bladder sphincter contraction
What is the primary function of a2 adrenoreceptors receptors during fight or flight?
- inhibit release of noradrenaline
- inhibit release of acetycholine
- inhibit release of insulin
What is the primary function of B1 adrenoreceptors receptors during fight or flight?
- ⬆️ Heart rate
- ⬆️ Inotrophic contractility
- ⬆️ Renin release (fluid and salt retention)
What is the primary function of B2 adrenoreceptors receptors during fight or flight?
- Vasodilation (skeletal muscle)
- Bronchodilation
- Gluconeogenesis (⬆️ glucose from liver)
Propranolol was the first ever beta blocker invented. What beta channels does in block?
- all as it is a non selective beta blocker
- inhibits B1 and B2 adrenergic receptors
What can Propranolol be used for in treatment?
- angina, hypertension, arrhythmias
- migraine, tremor
- anxiety
- thyrotoxicosis (excessive thyroid hormone)
What are beta blockers (specifically beta 1) able do to the heart in relation to BP?
- ⬇️ HR
- ⬇️ inotropic force
- ⬇️ afterload (SVR) through reduced renin release
What are 2 common side effects of beta blockers (specifically beta 1) that can occur?
- bradycardia
- fatigue
Why can beta blockers be dangerous in the lungs when using them to treat patients with heart disease?
- inhibit B2 adrenoreceptors
- bronchoconstriction
- ⬆️ breathlessness
- dangerous in asthma/COPD
Beta blockers (specifically beta 1) are useful drugs when treating the heart, but what are some side effects that they can have on arterioles in the circulatory system?
- ⬇️ blood supply to skeletal muscles
- ⬇️ blood supply to skin (cause claudication and cold hands)
- ⬇️ blood supply to penis
What is a useful method for remembering which beta blockers are present in the heart and lungs?
- B1 = heart - we have 1 heart
- B2 = lung - we have 2 lungs
What is the most commonly used B1 adrenergic antagonist, also called a beta blockers?
- Bisoprolol
Although Bisoprolol does reduce the side effects when compared with Propranolol, there can be one dangerous side effect in patients with diabetes. Hypoglycaemia causes release of adrenaline, causing gluconeogeneis in the liver in an attempt to release glucose. What symptoms can patient with diabetes experience when hypoglycaemic due to adrenaline?
- sweating, tremor, irritation and palpitations
- symptoms of adrenaline help patients know they may be hypoglycaemic
Why can it be dangerous for patients who are diabetic to take beta blockers?
- B1 adrenergic antagonist/blockers block symptoms associated with hypoglycaemia
- especially dangerous in non selective beta blockers
When treating hypertension, we need to remember how to calculate BP, which is cardiac output (CO) x systemic vascular resistance (SVR). Therefore what are the main effects on CO and/or SVR that adrenergic antagonists/blockers affect?
- CO
- ⬇️ inotrophy
- ⬇️ HR
- ⬇️ renin release
