Caffiene Flashcards
Examples of xanithine stimulants
caffiene, theophylline, theobromine
What is a methylxanthine?
a xanthine stimulant
Where does coffee come from?
the coffea arabica bush
tea
- camellia sinesis bush
- caffeiene and theophylline
coca
- theobroma cacao tree
- caffiene and theobromine
use of xanthine as an insectiside
comsumption of xanthine causes increased levels of octopamine
octopamine
an excitatory transmitter in the insect nervous system
What is caffiene an additive in?
- cola beverages
- over-the-counter painkillers
- cold remedies
- simulants
- energy drinks
primary form of administration for caffiene
oral
caffiene is primarily absorbed from the _____
intestine
At what dose do signs of toxicity appear?
1 gram (5 cups of coffee at 200mg/cup)
roues of administration for medicinal use of caffiene
suppository, injection, inhalation
At what dose is caffiene toxic?
greater than 10 grams (50 cups of coffee)
Time frame for peak blood levels of caffiene
30-60min
Maximal CNS effects occur in ____ hours
2 hours
Caffeine blood levels peak in _____ for cola beverages
1-2 hours
Why does it take longer for caffiene levels to peak when its from cola?
- the pH of soda (3.0) is less than coffee (5.0)
- the sugar is absorbed first, before caffiene
Half-life of caffiene
generally 3-5hrs, but there is much between-subject variability (genetic variation)
What organ metabolizes caffiene?
liver
What decreases the rate of elimination of caffiene?
- oral contraceptives
- pregnancy
What increases caffiene’s rate of elimination?
cigarette smoking
newborns & caffiene elimination
- excrete 85% of caffiene unchanged in urine
- caffiene has half-life of 4 days
- adult metabolism isnt developed until 7-9 months
What is theophylline used to treat in infants?
apnea
effects of caffiene on smooth muscle
-relaxation of involuntary muscles
What does caffiene do to bronchia?
relaxes them, a treatment for asthma
effects of caffiene on striated muscle
stimulation
What does muscle stimulation mean?
strengthen muscle contraction & reduce muscle fatigue
cardiovascular effects of caffiene
- constricts blood vessels in brain (headache treatment)
- dialates vessels in muscle
diuretic
increases production of urine
low doses of caffiene
- decreases drowsiness & fatigue
- more rapid and clearer flow of thought
moderate doses of caffiene
- nervousness, anxiety
- restlesness
- tremors
- insomnia
caffiene induced insomnia
increases the length of time to fall asleep, but does not alter normal sleep stages
high doses of caffiene
- convulsions
- increase rate & depth of breathing
What receptor does caffiene antagonize?
adenosine receptors
neuromodulator
adenosine; it acts in a more diffuse fashion than typical neurotransmitters
adenosines actions in the nervous system
down-regulates the activity of neurons
How is adenosine inactivated?
by uptake (into neurons &glia) and degredation
What can be produced from ATP? Where?
adenosine; pre-synaptically, post-synpaptically and in the extracellular space
Adenosine is part of what compund in every cell?
adenosine triphosphate (ATP)
ATP can also act as a _____ and is stored in _____
neurotransmitter, vesicles
What are the adenosine receptor subtypes?
A1, A2A, A2B and A3
purpose of receptor subtypes
provides a mechanism by which one neurotransmitter can produce a range of effects
Besides the existence of receptor subtypes, what else proivdes diversity in signaling?
differential distriubtion of receptor subtypes in different areas of the brain
Are adenosine receptors ionotropic or metabotropic?
metabotropic
A1 and A3 are linked to _____
inhibitory G proteins (Gi)
A2’s are linked to
stimulatory G proteins (Gs)
Effects of adenosine at A2 receptors
- Adenosine (first messenger) binds to A2 receptor
- A2 receptor activates Gs protein
- Gs protein excties the enzyme adenylate cyclase
- Excitation of adenylate cyclase promotes converstion of ATP to cAMP
- cAMP (second messenger) excites protein kinase
- protein kinase opens Ca channel located in the membrane adjacent to A2 receptor
- Ca2+ enters the cell
effects of adenosine on A1/A3 receptors
- adenosine (first messenger) binds to A1/A3
- A1/A3 receptor activates Gi protein
- Gi protein inhibits adenylate cyclase
- Prevents conversion of ATP to cAMP, cAMP activating kinase, kinase opening Ca channel and Ca from entering the cell
Where are many A1 receptors located?
presynaptic terminal
Adenosine acts at _____ receptors to inhibit ____ and decrease the release of _____
presynaptic A1 receptors; Ca2+ influx; dopamine, norepinephrine & acetylcholine
effects of adenosine on postganglionic NE neurons of synmpathetic nervous system
decreases release of NE, decreases heart rate and respiration
effects of adenosine of mesoaccubens & nigrostriatal DA neurons
decreases DA release, decreases reinforcement and motor activity
effects of adenosine on NE and ACh in cortex
decreases the release of NE & ACh, decreases alterness
caffiene on sympathetic NE neurons
increases release of NE, increaes heart rate and alertness
caffiene on mesoaccumbens & nigrostriatal DA neurons
increases DA release, increases reinforcement and motor activity
caffiene on NE and ACh in cortex
increases release of NE and ACh, increasesarousal and alterness
Other effects of caffiene:
- inhibits action of certain enzymes
- blocks GABAa receptors
- promotes CA2+ release
Do A2A and A2B receptors have the same sensitivity to adenosine?
No
