Migraine: Treatment And Prevention (Fitz) Flashcards
What is migraine?
Primary disorder of pain
Special form of neurovascular headache
Neural events provoke dilation of cranial blood vessels, which result in pain, further sensory and central nerve activation
Describe the migraine time course
Prodrome: Premonition 12-36 hrs before headache: yawning, depression, lethargy, excitability, craving, distaste
Aura: classic
None: common
Headache: Mostly unilateral ~4-72 hrs Photophobia Phonophobia Nausea Vomiting
Postdrome
Exhaustion
Fatigue
Describe therapeutic agents for migraine
Goal: rescue from/halt migraine attack
Frontline agents: triptans: 5HT1B/1D receptor agonists in prodrome phase
Ergot alkaloids in prodrome phase
Headache phase: NSAIDS, acetaminophen
Describe preventative agents for migraine
Goal: limit frequency and severity of attacks
In asymptomatic phase
Beta-blockers: propranolol, timolol
Tricyclic antidepresseants: amitriptylene, imipramine
Anticonvulsants: topirimate, valproate
Ca2+ channel blockers: verapamil
Describe neurogenic inflammation theory of migraine: cortical spreading depression
Wave of electrical activity and H+, K+ passing through nerve cells stimulates release of neuropeptides (CGRP, substance P) and inflammatory mediators (NO, histamine, prostaglandins) that dilate cranial blood vessels and sensitize nerves to pain
Sensitization of nerves progresses from periphery to brain
What are the elements of a migraine attack?
Vascular: cerebral and cranial vessels. Meningeal and dural arteries
Sensory nerves: trigeminal nerves and ganglion and trigeminal nucleus caudalis
Brain: cortical spreading wave
Brainstem: distorted sensory input
Neurogenic inflammation: neuropeptides (CGRP), nitric oxide (NO)
Serotonin receptors: 5HT1B/1D
Describe the mech of a migraine attack
- Brainstem dysfunction sparks a wave of excitation/depression in cortex (CSD)
- Cerebral vasoconstriction accompanied by H+, K+, NO discharge from neurons - Electrolytes and NO diffuse and dilate cranial arteries and depolarize perivascular trigeminal terminals
- CGRP and neuropeptides promote neurogenic inflammation - Neurogenic inflammation irritates TG nerve and transmits migraine pain
What are the two key mediators in migraine?
CGRP and NO
They interact throughout trigeminal neurovascular system
-at crainial artery, ganglion, nucleus caudalis
What drug used to treat coronary artery disease provokes migraine?
Organic nitrates (NO)
Cranial vessels and presynaptic TG nerve terminals express a distinct subset of what receptors?
Serotonin 5HT-1 receptors:
5HT-1D peripheal neuron
5HT-1B cranial vessels
5HT-1B/1D central neuron
Therefore, serotonin and its receptors modulate CGRP actions
Triptans are selective serotonin 5HT-1D/1B receptor agonists. What does triptan binding to 5HT-1B receptor do?
Lowers cAMP Stimulates vasoconstriction (opposes vasodilation)
What does triptan binding to 5HT-1D receptor do?
Lowers cAMP
Inhibitos presynaptic release of CGRP
Describe the peripheral actions of triptans
Triptans cause vasoconstriction of dilated meningeal, dural, and pial blood vessels by stimulating 5HT-1B receptors located on vascular smooth muscle
Triptans inhibit release of CGRP and other neuropeptides from peripheral end of trigeminal nerve by stimulating 5HT-1D receptors on presynaptic nerve terminals
What are the brainstem actions of triptans?
Triptans also have high affinity for 5HT-1D receptors located centrally in region of trigeminal nucleus caudalis in brainstem
This modulates incoming painful sensory information from periphery and inhibits its upward transmission to thalamus and higher brain centers where pain is perceived
Triptans are 5HT-1B/1D agonists. Do not confuse them with what other serotonin receptor (ant)agonists?
5HT-1A agonists: anxiolytic, antidepression (buspirone)
5HT-2 (serotonin): aggregates blood platelets
5HT-3 antagonists: anti-emesis (ondansetron)
5HT-4 agonists: GI disorders (cisapride)