Nicotinic Receptors Flashcards
Where are nicotinic receptors found?
Gangli + nmj (they’re different)
Nicotinic receptor general characteristics
Pentamer with integral ion channel
Drugs affecting ganglia don’t discriminate between ____ + __________
Sympathetic + parasympathetic ganglia
Characteristics of nicotine including effects at small and large doses
- Stable, volatile tertiary amine
- Readily absorbed through mucous membranes + skin
- Stimulates ganglia in small doses
- Blocks ganglia at larger doses
Main acute effects of absorbing nicotine by smoking
- CNS stimulant effects
- Increased parasympathetic and sympathetic activity
- Release of ADH of posterior pituitary gland
In what ways is parasympathetic and sympathetic activity increased by smoking?
- Rise BP
- Tachycardia
- GI motility inhibitied
- Increased salivation + bronchial secretion
- Vasoconstriction (impairment in foetal growth?, increase in cardiovascular disease?)
If smoking doesn’t cause ganglionic block, what can?
Chewing tobacco
How do ganglion-blocking drugs act?
- On postsynaptic receptor, either as competitive antagonists/ open channel blockers/ mixture of both
- Selective for autonomic ganglia
- Don’t affect neuromuscular transmission
- Don’t distinguish between sympathetic + parasympathetic action
Effects of cardiovascular system block
Depends mainly on sympathetic system
- > dilation of arterioles + veins + loss of cardiovascular reflexes
- :> skin vasodilation
Effects of GI block
Mainly parasympathetic
- inhibition of motility and secretion -> constipation (severe)
Effects of genito-urinary system block
Parasympathetic block -> impairment of micturition + erection failure
Sympathetic block -> inhibits ejaculation -> impotence
Effects of eye block
Loss oc accommodation + pupillary reflex -> photophobia
Hexamethonium use
No longer used in man but first effective antihypertensive 1949 - too many side effects
Trimetaphan
Produce controlled hypotension during surgery occasionally
